# Audi TT Quattro 225 Haldex Issue



## Christian_02_225 (Sep 20, 2016)

Hello, i am new to this forum and have heard positive things about it. I have a 2002 Audi TT Quattro 225 and I love the car despite the usual Audi problems, other than that, the car runs great and there is no major problems with it. My Haldex system does not seem to be performing correctly, I have put it on jack stands and all 4 wheels spun but I get bad wheelspin or power loss from ESP when driving "spiritedly". I know it is engaging but do not think it is providing sufficient torque to spin the wheels from the weight of the car since it did spin on the jacks but does not feel working on the street. I do not know the last fluid change, but there is fluid inside, and considering the car has 170k on it with a rebuilt motor, I expect some problems but would like to at least find out what is wrong with the Haldex since it is a major feature to the car that i am missing out on. Any advice would be appreciated Thanks!


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## asiwa (Dec 18, 2014)

Hey man! 

First of all, welcome to the forum. We do have a great community here and I hope you'll find everyone's advice both helpful and insightful.

The Haldex system in the MK1 TT can be glorious at best and downright frustrating and maddening at worst. Especially with such a high mileage car, I would recommend checking out the following things:

-Haldex fluid/filter - make sure you do a change right away. The fluid/filter service is something that owners and even dealers tend to forget about and could have been neglected for a long period of time. You can get the tube of fluid and filter from any Audi/VW dealer .

- ESP/ABS Codes - Bad sensors and ABS modules account for a fair chunk of Haldex issues. If either system is working incorrectly and throws a code in the ECU, the system will drop to front wheel drive only until the parts are replaced and the codes are cleared. These codes can be checked with VCDS/VAGCOM.

- Haldex control module - The physical computer module that controls the pressure on the clutch pack is notorious for failing due to exposure/vibration/fluid leakage/etc. This is the problem that my particular car had. The modules can be bought new for way too much money or you can find one used fairly easily for under $200. Make sure you get one off of a low mileage car, if possible. Also be sure that it wasn't chopped off (check pictures to make sure that the cables and connectors are intact). The module can be read for codes and tested for functionality from VCDS as well.

Other small assorted issues - any part that is interconnected with the Haldex system can cause problems. Things like the brake light switch under the brake pedal, clutch pedal switch, and the ground strap that connects the Haldex casing to the car chassis can all cause the system to fail. Most of the solutions are straightforward, but diagnosing the actual problem can be the hard part. VCDS is your best friend, if you can get it or have access to it.

I'm a bit short on time and don't have the ability to write more at the moment, but if you have questions or want specifics feel free to ask. Everyone here is happy to help!

Sent from my Nexus 6P using Tapatalk


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## Christian_02_225 (Sep 20, 2016)

Hey, thanks for the quick reply, there are not any codes according to the obd ii scanner i have but the ground strap on the haldex was disconnected when i first go it and fixed that, but like i said, the haldex IS engaging but i guess once on the ground, it just doesnt have enough pressure on the packs maybe? Would an overdue filter/fluid change cause these symptoms? Once again thanks for the reply and advice. 
Thank you


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## MCPaudiTT (Nov 26, 2006)

Change the fluid and filter. They are a FREQUENT maintenance item, and it sounds like you don't know the status. When in doubt, change it out. If that helps, great! If not, come back and post up is any changes were noticed. You can also try these diagnostics: http://wiki.quattroworld.com/index.php?title=TT.Mk1_Haldex_Troubleshooting


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## asiwa (Dec 18, 2014)

The issue you're experiencing is actually identical to the problem I was having. My car is an early '01 225QC, so it doesn't have ESP and the previous owner(s) didn't opt for that part of the recall.

MC is right about getting the fluid and filter done. I am personally doubtful that the fluid itself is the cause for malfunction, unless the system was run dry or almost dry and caused excessive heat and wear which is a rare occurrence. I do have a whole shpeal that I give about the Haldex but it's better at this point to take the issue one solution at a time.

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## Christian_02_225 (Sep 20, 2016)

Okay guys thanks for all of the replies! I do recall trying the rollout in the parking lot and I did not do it correctly if i remember right, but I did hear a sound similar to a power steering pump but with out the whine, and also it sounded like something was dry and heard a variety of very light clicks and taps. I am pretty sure that this sound was the haldex trying to engage but it did not sound so healthy. It is too late as of right now to go test it again but I will do it the proper way, and let you guys know! I am probably going to do the fluid/filter change. How difficult is this process and what am I looking at as far as price? Thanks again guys!
Oh and one time I did crack the drain plug slightly open just to make sure the system was not bone dry, and there was indeed fluid in it, but i do not know what kind of viscosity the haldex fluid is supposed to have but it seemed relatively thin in my opinion.


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## MCPaudiTT (Nov 26, 2006)

Fluid and filter is NOT something you should "probably" do - it is the ONLY think you have available as your next step. There is NO Point in doing any other troubleshooting at this point until you change the fluid. It should not be thin, it is relatively thick, and if the viscosity is wrong, or if the fluid is contaminated, or ... your Haldex won't work right even if EVERYTHING else is fine.


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## bwdz (Jan 21, 2015)

The clutch plates are usually pretty tough so the usual culprit is a weak charge pump when the wheels just won't grab. It would be good if you posted up your location and someone who has VCDS can scan it for you, your OBDII scanner is not scanning the Haldex system. VCDS lets you run a test on the system and shut the pump on and off from your laptop as well as test communication with the controller. You can drive down the road with VCDS and see if all your ABS sensors are reading the same Etc....


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## asiwa (Dec 18, 2014)

MCPaudiTT said:


> Fluid and filter is NOT something you should "probably" do - it is the ONLY think you have available as your next step. There is NO Point in doing any other troubleshooting at this point until you change the fluid. It should not be thin, it is relatively thick, and if the viscosity is wrong, or if the fluid is contaminated, or ... your Haldex won't work right even if EVERYTHING else is fine.


As I recall from my last fluid change, the Haldex oil is actually very thin and runny even when fresh. It sloshes around fairly easily in the factory container. Used fluid will be even thinner but really not by much - if anything it will just be slightly darker from regular wear inside the system. All of this is a result of the "oil" not actually being oil in the first place; it is hydraulic fluid that is used to apply pressure to the clutch plates.

The above comment is also a route to check out; I completely forgot to mention the precharge pump. That was another fix that I took care of and while mine did need to be replaced, it was ultimately not the prevailing issue with my car.


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## Christian_02_225 (Sep 20, 2016)

Okay I have finally done the oil change. Like I expected, no difference. I started researching a bit more and have came to the conclusion that I am pretty sure my pre charge pump is weak. I have put the car on jack stands before and the wheels spin, but since there is no resistance to the rear wheels since the car is in the air, I think that the precharge pump may be weak, since it is for a fact engaging, I just maybe think that it could be old and worn out and not providing sufficient pressure to the rear wheels. Any help will be appreciated and I heard these motors are pretty pricey, I also heard that ordering a Volvo haldex pump will be much cheaper. I do not need OEM or anything, but I just want my haldex to work. And with me considering a chip, maybe APR or REVO, I would really like the extra traction. I feel like I am missing out on a fun feature of the car, and would really like to make this thing work. Thanks
PS what chip do you guys recommend for reliability, and performance gains (yes i know both are rare) but input is appreciated Thanks again


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## bwdz (Jan 21, 2015)

SO you think your awd is not engaging, but it did on jackstands. One simple test you can perform before going any further would be this, go drive down the road "spiritedly" like you mentioned so that the esp kicks in from tire spin, go back, pull the haldex fuse which will definitely disengage the awd and do it again. See if it is much different or if it is about the same. This would tell you if it is working at all or not at all.


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## recaro19 (Feb 17, 2016)

Get it hooked up to a computer. I'm assuming this is the only real way to tell without causing more damage.

Maybe research some codes that may pop up in regards to this issue? Have you taken it to a mechanic?


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## bwdz (Jan 21, 2015)

Where are you located, many of us have VAGCOM and can scan the system for you. If you want, send me a PM with your email and I can forward you a PDF file of the factory service procedure with all the pinout readings you need to get on the plugs and the test and service procedure.


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## Christian_02_225 (Sep 20, 2016)

Okay, it has been a while since I had been concerned about this Haldex Unit, and out of the blue last night I was browsing eBay and found a complete haldex carrier assembly for only 179.99 plus shipping which was 125. I ended up getting it for 149 plus shipping by making an offer. I had to snatch it since they are usually 500-600 dollars or more, and it came with a 6 month money back guarantee. My question would be, how difficult would it be to swap the entire carrier assembly, and could you refer me to a write up on it? Thank guys


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> Okay, it has been a while since I had been concerned about this Haldex Unit, and out of the blue last night I was browsing eBay and found a complete haldex carrier assembly for only 179.99 plus shipping which was 125. I ended up getting it for 149 plus shipping by making an offer. I had to snatch it since they are usually 500-600 dollars or more, and it came with a 6 month money back guarantee. My question would be, how difficult would it be to swap the entire carrier assembly, and could you refer me to a write up on it? Thank guys


That's definitely priced significantly lower than most rear assemblies I've seen, but I am really questioning the desire to swap the whole assembly out on your car (assuming you haven't done any further troubleshooting).

These problems are usually due to a failure of one or two very small electronic components in the Haldex system as a whole. This purchase means you have a spare in the event that your rear end implodes, but that really doesn't happen on these cars unless you:

- Run the system with no fluid
- Never change the fluid or filter (even then the innards are pretty hefty)
- Abuse the car on a dyno
- Abuse the car on the street
- Use a poorly implemented aftermarket Haldex pressure controller

In light of this, swapping the rear end on your car will absolutely be more work than it's worth. Did you try rebuilding/replacing the precharge pump or swapping out the controller? Both of those fixes take far less time and hassle and are almost always the cause of malfunction.

Also - I have seen rear assemblies on ebay in the past for that price and they *always* have had the Haldex controller removed prior to being sold. Did you make sure this one you purchased had that *very important* part still attached?


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## Christian_02_225 (Sep 20, 2016)

Well the reason I replace the whole thing is becuase; number one, I dont wanna go through all of the work doing possibly clutch packs, pump, controller, etc and still not have a functioning haldex system. I would rather spend 275 and do it once and have it work guaranteed, than spend 200 on a pump, 70 on fluid and filter and clutch packs are i am sure an expensive unit too. Plus the work to split the haldex open and actually make it work. I saw the low price and i just had to take it. I really just want this AWD to work. Mainly becasue i have a 225HP and low profile front tires so traction is limited. I also don't like having to push the ESP button everytime I want to go fast without getting the boost cut. Not that there is any snow in South Carolina but I just would rather have AWD working because im planning on taking it to the drag strip and without the haldex working, then I would have no chance. It would have less wear on my front tires, better launches, and not that annoying traction control power cut. Thanks for your consideration though. It sounds like you know your way around Haldex units so when I get mine removed if you want to snag it you might wanna take it off my hands. It just depends, if it is something simple like the precharge pump, then I will just send it somewhere to get the motor fixed and then maybe sell the unit for a good price. I mean could I atleast get 150 bucks out of my broken one as is? Anyway thanks again. Tell me what you think, oh and is there anywhere i can find a guide to removing it and reinstalling it? Thanks !!!!!


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## bwdz (Jan 21, 2015)

Just to clarify something, you say you have low profile tires on the front? Do you have the same size all the way around? Just checking


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## Christian_02_225 (Sep 20, 2016)

I indeed do have different tires sizes. 215 40 18 on the front and 245 40 18. Weird combo but i kinda like it. I looked it up and supposedly only a 3.6% rolling diameter difference. I heard they can be safe 4 - 5 %


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## bwdz (Jan 21, 2015)

Oh that is a big difference and probably tore up your system, I know they say that it is allowed but your rears are nearly an inch taller. BTW, running a smaller tire on the front which carries 60% of the weight of the car vs the rear is not recommended and will make your car handle extremely poorly, any car that is front heavy should not be running a smaller tire in front.


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## YayItsBlake (Apr 11, 2016)

^ Im with this guy. 

Staggering your tire width while maintaining uniform height all the way around is one thing, two entirely different tire sizes is another. 

You're essentially running a tire setup for a chevy camaro, not a primarily fwd car with awd secondary. Like bwdz said, at BEST you're looking at 60/40 distribution, what sense does a taller, meatier tire in the rear make? 

I'd spend the $275 to get some matching tire sizes, then go from there. I'd rather drive in a properly balanced fwd setup than understeer/traction/esp nightmare mode. You would be suprised the difference having matching wheel speeds will make in a system that is constantly looking for them. 

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## bwdz (Jan 21, 2015)

Not sure if you have VCDS, but if you do pull up your ABS sensors as you can read them individually. When the car is in a straight line as I am driving I am reading the exact same reading on all of mine but if my rears were an inch taller the computer would constantly be trying to adjust for the slip. Maybe your system is not burned out it's just fighting readings that are off.


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## Lorem (Nov 19, 2003)

Here's my post in the U.K. TT forum. 
http://www.ttforum.co.uk/forum/viewtopic.php?f=2&t=1413065

Here's Video.
https://youtu.be/2I31rD3t35s

While you're in this area check the flat grounding cable found no the driver side above Haldex. My was heavily corroded and it was easy to clean up and replace with new wire.

I'm sure the rear diff fluid is well overdue and need to replace as well. Unbolt the top/side fill plug first before drain plug. Just incase fill hole is stuck.


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## Christian_02_225 (Sep 20, 2016)

Okay guys I havent checked on here in a little bit but just to recap, the haldex works while on jackstands but doesnt kick in like it should on the ground. I will be solving the tire diameter issue by putting 245 35 18s on the back and according to a website that is a complete diameter match to my 215 40 18s in the front. I am changing the rear end regardless, I am not interested in trying anything else on this old haldex in my car now. I would rather do it once and have a guarantee to have it work than to just to keep shooting in the dark. thanks for the input but i have just had enough with it. Thanks


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## bwdz (Jan 21, 2015)

I would change to the 35 series tires and just see how it works with that. If it still doesn't work I can't blame you for just popping it all out since you already have the replacement pieces and you got them for a steal.


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> Okay guys I havent checked on here in a little bit but just to recap, the haldex works while on jackstands but doesnt kick in like it should on the ground. I will be solving the tire diameter issue by putting 245 35 18s on the back and according to a website that is a complete diameter match to my 215 40 18s in the front. I am changing the rear end regardless, I am not interested in trying anything else on this old haldex in my car now. I would rather do it once and have a guarantee to have it work than to just to keep shooting in the dark. thanks for the input but i have just had enough with it. Thanks


I think I can speak for most TT owners when I say that we all understand your frustration with the Haldex issues, but one of the points I tried to make was that even after purchasing an entire rear assembly for your car there is absolutely no guarantee that things will be any different.

I asked if you knew if this assembly came with a working Haldex controller and didn't receive an answer. If it comes with a bad one, or doesn't come with one at all, you will be in the exact same place you were before but will be out of a lot of time and work. This is why members recommended finding someone to try and diagnose your car with VCDS. One scan can sometimes tell you exactly what's wrong.

Keep in mind that this assembly was removed from a used car, possibly with more miles than the car you have right now. There is always a chance that the replacement has the same problems or more.

This isn't supposed to be negative in nature - I just don't want you to perform a difficult service on your car when there are several easy and inexpensive fixes that combined take up less time than the swap will. 

Regardless, let us know how it goes. Everyone deserves a working Haldex no matter the situation. Good luck, bud.


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## Christian_02_225 (Sep 20, 2016)

The Haldex came in yesterday but it was shipped to my Dad's dealership so I will be looking at it today after school. I kind of jumped the gun when ordering it since it came with a 6 month guarantee so if it did not work then it would not be a waste of money. I have a picture of the haldex and I think i can see some of the loom that would come from the controller but i am not 100% sure yet, and When you say controller, you mean the computer part of the haldex right? Or the haldex coupling itself. It definitely comes with the coupling lol and like i said, pretty sure it comes with the controller. When I first got the car, the ground strap was indeed broken, but was replaced, and that did not seem to fix it. But what makes me think that it is mechanically related such as clutch packs is the fact that it engages while off of the ground but I think when the weight of the car is put on the haldex, then it does not have enough strength to actually put power to the ground. It could be the clutch packs, or the stepping motor, Which are both more expensive than what i spent on the whole carrier assembly, and there is no guarantee that one of those are bad either. When I remove the old haldex from my car, then I will probably try to salvage it or sell it as is just to get some of my money back. I mean it has to be worth something right? I know that you guys are trying to help me, and I really appreciate that but I just want to get it DONE and working lol. Thanks again


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## Christian_02_225 (Sep 20, 2016)

Also, just to add I did the rollout test in the parking lot where you drive in a circle and rev it up. I remember doing it once and hearing a grinding/ rotating noise from the rear end. Not to mention, the car stopped in the same distance in both scenarios of the test.


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## Christian_02_225 (Sep 20, 2016)

Okay, quick update. After vacation I came back and switch to the proper matching rear tires. I now have 215/40/18s on the front and 245/35/18s on the back. The sizes are a perfect match in rolling diameter. As I expected, no difference in the Haldex, (I did not plan on having any difference anyway since it was broken). I recieved the Haldex Unit assembly and cleaned it up. It does come with the controller and everything I need to change it except that the plug is all messed up from when they removed it. I do not know if it is supposed to look like it does but it is just a connector with a bunch wires coming out of it. Anyway, I was wondering if it would be easier to just pull the haldex unit itself from the diff in the car and switch it with the new one. Would I need a new gasket for the haldex to differential if i did do that? I figured that if I just took off the haldex, I would not have to undo the axles and any other things. Also, what kind off differential fluid does the diff take, there was a rubber plug on top of the diff and it was shipped upside down so when I got it, the diff fluid had all leaked out. I am really excited to get this working, I just want to take the most logical route. What do you guys think? Thanks so much guys


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> Okay, quick update. After vacation I came back and switch to the proper matching rear tires. I now have 215/40/18s on the front and 245/35/18s on the back. The sizes are a perfect match in rolling diameter. As I expected, no difference in the Haldex, (I did not plan on having any difference anyway since it was broken). I recieved the Haldex Unit assembly and cleaned it up. It does come with the controller and everything I need to change it except that the plug is all messed up from when they removed it. I do not know if it is supposed to look like it does but it is just a connector with a bunch wires coming out of it. Anyway, I was wondering if it would be easier to just pull the haldex unit itself from the diff in the car and switch it with the new one. Would I need a new gasket for the haldex to differential if i did do that? I figured that if I just took off the haldex, I would not have to undo the axles and any other things. Also, what kind off differential fluid does the diff take, there was a rubber plug on top of the diff and it was shipped upside down so when I got it, the diff fluid had all leaked out. I am really excited to get this working, I just want to take the most logical route. What do you guys think? Thanks so much guys


Here's the issue: you need that connector to be intact to have any shot at a working Haldex.

These are the sorts of things that you need to be 100% sure of before you buy things from wreckers and salvage yards. Frequently they hack through wires and yank pieces apart that are crucial to the part's normal operation. You now will need to find the kit to replace/repair that connector as it insulates the controller connection from condensation/dust/dirt/oil/other debris. 

Second - when you do get that connector fixed - the *more* logical approach at this point would be to swap out your controller and precharge pump with the ones that came with the unit you purchased. These jobs take very little time and will quickly eliminate the fixes that have already been suggested in this thread without you having to waste your time swapping out the entire differential and Haldex.

Provided that for some reason those swaps do not fix the issue, you could do the assembly swap if desired. There are good writeups on the TTForum and on the Vortex on the removal of the assembly. Generally, the idea is to remove the differential and Haldex as one piece as they are very difficult (if not impossible) to *properly* separate and reattach while still mounted on the car. If I remember correctly there are a couple one-time-use parts that need to be replaced. I will look around for a writeup and post one soon.

Most people recommend Redline synthetic oil for the diff in our cars. I would probably do the same if I were going to service it soon.


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## bwdz (Jan 21, 2015)

A broken plug makes it no good. Can a plug be replaced and repaired, sure but you do it incorrectly and introduce any sort of additional resistance to the circuit and it will not function properly. All along you said you are replacing the whole thing rather than do what we suggested and what you are suggesting now (meaning just trying the module before swapping all of it)
Anyway, instead of saying I told you so I'll help you. There is a "gasket" in there. It is like a metal crush gasket not a rubber one. I think its about $10 so get one before you start the job. Also get some fresh Haldex fluid and a filter so when you spill some while doing it you can replenish the fluid. I would tell you that you can just top it off a bit but the only way I know of putting fluid in the Haldex is through that bottom plug by injecting it up there so I cannot figure out how you would just add some when you pull out the plug it all leaks out. Also I never heard of anyone mentioning how you can check the level, I was always under the impression that the tube of fluid you buy is the amount that should be in there so drain it out and inject the new tube.


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## Christian_02_225 (Sep 20, 2016)

Okay so I am going to consider changing the pre charge motor since I have a "hopefully functioning" one on the new one. I attempted to remove it in the past but I could 

not get any clearance between the electric motor cover and the driveshaft/ subframe to get it out. Last time I did this, i dont think that I got much fluid back in the unit 

when I drained it for the motor removal but my only concern would be that the haldex coupling would be ran with very low fluid for over a month or so, I just don't wanna 

spend money on more fluid to add to the existing unit in the car if it could possibly be damaged by running it super low on fluid for a little over a month now. Anyway, would 

I just have to remove the driveshaft to get clearance for the motor to come out? I don't really mind doing it now that I have a replacement but I heard that people have 

pried the rubber driveshaft cover to get clearance but i do not want to mess anything up. Just let me know, thanks guys.


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## bwdz (Jan 21, 2015)

How are you going to know anything if the fluid is low? Maybe it will malfunction because of low fluid as the pump might not get enough to properly charge the system. There is not a whole lot of fluid that goes in there.
Honestly, from your posts, I think you need some guidance. Sounds like you have mechanical aptitude but no way in hell should you be doing these things without someone trying to get you to do it right.


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## asiwa (Dec 18, 2014)

bwdz said:


> How are you going to know anything if the fluid is low? Maybe it will malfunction because of low fluid as the pump might not get enough to properly charge the system. There is not a whole lot of fluid that goes in there.
> Honestly, from your posts, I think you need some guidance. Sounds like you have mechanical aptitude but no way in hell should you be doing these things without someone trying to get you to do it right.


Agreed.

When you do services on the Haldex that require removing the pump and/or controller, you are preparing to purchase a new tube of fluid every time. I made this mistake when I did the troubleshooting on my own car. I did the precharge pump and two controller swaps in rapid succession and ended up going through three tubes in less than a month. Draining/refilling the unit is good practice to ensure you don't run the system dry when you service it.

The people in this thread have made many recommendations about how to go about troubleshooting the Haldex problems on your car, and most are speaking from personal experience. Although what you do is 100% your decision, you've opted to mostly disregard that advice and go your own route. 

We want to help and make sure you get the job done right but that requires doing things in a sometimes very meticulous and specific way. When you bought a used MKI TT you nonverbally agreed to buying a car with weird quirks and an uncommon drivetrain system. Owning and maintaining that requires you to sometimes buy fluid when you don't want to or do things more than once to get it right. 

We get it - you don't want to waste time, but it took me personally over a year to get the problem solved and now that I took the time to do it I haven't had any problems since. Sometimes you just need to bite the bullet and do it.

Edit: An addition - you can pry the driveshaft cover back with a crowbar/breaker bar or some other sturdy item. I had the same problem with my car and the solution was pretty simple. You can use a fair amount of force on it, too.


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## Christian_02_225 (Sep 20, 2016)

Okay, although I might not be the most experienced person working on cars, I am still learning. I think that it is low on fluid because when I tried to use the siphon to put back in the new fluid I just put in the other day. I was not going to buy a whole new tube of fluid if it is not going to function anyway. I know that might not have been the most logical decision but with what I had to deal with at that time, that was my only choice. There is still fluid in there but just not near as much as there should be. If it is not engaging anyway, I do not think that it could do too much harm IMO. I am going to go ahead and try the motor to see if it will fix it. And once again, i know I do need some mechanical guidance, and YES that's why i am here lol. And all I need to know is if driving with a non engaging haldex with low fluid for a little over a month will cause it to completely go out, or should i be safe, there is no binding in the rear end and it drives just like it did before. Thanks guys i really do appreciate your help


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> Okay, although I might not be the most experienced person working on cars, I am still learning. I think that it is low on fluid because when I tried to use the siphon to put back in the new fluid I just put in the other day. I was not going to buy a whole new tube of fluid if it is not going to function anyway. I know that might not have been the most logical decision but with what I had to deal with at that time, that was my only choice. There is still fluid in there but just not near as much as there should be. If it is not engaging anyway, I do not think that it could do too much harm IMO. I am going to go ahead and try the motor to see if it will fix it. And once again, i know I do need some mechanical guidance, and YES that's why i am here lol. And all I need to know is if driving with a non engaging haldex with low fluid for a little over a month will cause it to completely go out? Thanks guys


I would generally not advise running the car with low fluid in the coupling. Even though the clutch pack/controller may not be working properly, the fluid serves multiple purposes. It serves as a hydraulic fluid for pushing the clutches together, but also serves as a lubricant/coolant for the system since it is a wet clutch design. If you drive the car with low fluid you run the risk of damaging the internal components whether or not they are operating the right way.


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## Christian_02_225 (Sep 20, 2016)

Well i know that it is not good for it regardless hahahaha but do you think it will be okay if i were to just put another full tube in when i do the motor? Oh, and I never really drive the car for really long road trips at a time so I don't think that too much wear could have been caused by heat (just a guess) .... school is 5 minutes away every day, not that school is my only destination but it's not like i am driving for super long periods of time every day. I just want to make sure that it would be worth my time trying the motor. I am probably gonna do it anyway now that i know that you can just pry the driveshaft rather than removing it which was what scared me in the beginning. I have seen a few posts online where people have ran them pretty much dry due to a leak and did not really seem like the haldex grenaded during that process. Much Thanks


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## mdjenkins (Feb 16, 2010)

Risk the cost of a Haldex or walk to school?
Based on the half measures you've taken to troubleshoot in the name of funds, I know which side I would recommend and which I bet you'll do.

Either way, its your car and your risk. Hope it all works out for you.


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## bwdz (Jan 21, 2015)

Christian_02_225 said:


> Well i know that it is not good for it regardless hahahaha but do you think it will be okay if i were to just put another full tube in when i do the motor? Oh, and I never really drive the car for really long road trips at a time so I don't think that too much wear could have been caused by heat (just a guess) .... school is 5 minutes away every day, not that school is my only destination but it's not like i am driving for super long periods of time every day. I just want to make sure that it would be worth my time trying the motor. I am probably gonna do it anyway now that i know that you can just pry the driveshaft rather than removing it which was what scared me in the beginning. I have seen a few posts online where people have ran them pretty much dry due to a leak and did not really seem like the haldex grenaded during that process. Much Thanks


Naah, it won't hurt a thing. As a matter of fact I recommend you run all your fluids low, drain some engine oil out of it and run that low for a while and same with trans fluid heck even coolant is probably not all that necessary. Best one would be brake fluid, it weighs too much and all it does is slow you down, run that real low as well.


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## Christian_02_225 (Sep 20, 2016)

Well that's a no brainer, duh!! Weight reduction BRO! I never put fluids in the car, right ? lololol But for real, yes i know it is not the smartest thing to do but I probably am going to get fluid today and possibly going to try to do the motor depending on how I feel. I will let you know how it goes, and YES i have a full bottle of brand new fluid ready to go.


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## bwdz (Jan 21, 2015)

I tried using sarcasm to get the point across so you don't burn it up. That fluid is cheap insurance


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## Christian_02_225 (Sep 20, 2016)

No, i got what you are saying but today i am changing the motor and putting a complete bottle of fluid in this time lol. I will let you guys know how it goes. Just to recap to be sure... I undo the 2 allen motor cover bolts, unplug the motor, drain the remaining fluid, pry the driveshaft cover, pull the motor out, and then the reverse. Right? am i missing anything major in the process


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## Christian_02_225 (Sep 20, 2016)

okay, yesterday I changed the pre charge pump with the one of off my new unit that i got. I was really hoping that the motor would be the trick to fix it but apparently not. I still got the same amount of wheelspin/ power cut as i did before. I tried the rollout test in the parking lot and could hear a bad noise like something was trying to engage and the traction light cut all of my throttle control. I think something internal is just toast in the unit. I do not think me running it low with any fluid caused this because when I did this test about 8 months ago, I heard the same exact sound when doing this test with identical results. I put a completely full new bottle of haldex fluid in the unit and had barely ANY spill out when re inserting the drain plug. Any ideas at this point? There was not any metallic flakes in the fluid that i extracted or anything suspicious that would worry me but at this point i really do not get it. Also, if it was the controller unit, wouldn't it just flat out not work? What do you guys think? :banghead:


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## bwdz (Jan 21, 2015)

That noise you hear is sometimes the ESP trying to work the brakes when it thinks something is slipping. Run a VCDS scan, there is also a test for communications with the controller in the VCDS and it will cycle the pump on and off during it's diagnostic of the Haldex..


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## Christian_02_225 (Sep 20, 2016)

Okay, that makes me feel a little bit better, I was wondering why the noise was not exactly coming from the back of the car, more towards the front. I will have to find someone with a VCDS or get one. How much could I like make one for? Is it not just a software and an OBD-II to USB cable? I would like to have one for myself but I also heard that the software is pretty expensive. Where can I get the software for the cheapest price? Oh, and also do you think that it could possibly be the controller now? At this point what else is there to replace. I mean could an old filter cause this? I have done the oil changes but have not touched the filter. Could a really old filter possibly cause it to not work like this? Thanks!

Edit: The new unit that I got has a controller too so I could maybe try that? I have read online that a clogged filter could cause a computer malfunction? idk but I really need to get my hands on a VAG-COM


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> Okay, that makes me feel a little bit better, I was wondering why the noise was not exactly coming from the back of the car, more towards the front. I will have to find someone with a VCDS or get one. How much could I like make one for? Is it not just a software and an OBD-II to USB cable? I would like to have one for myself but I also heard that the software is pretty expensive. Where can I get the software for the cheapest price? Oh, and also do you think that it could possibly be the controller now? At this point what else is there to replace. I mean could an old filter cause this? I have done the oil changes but have not touched the filter. Could a really old filter possibly cause it to not work like this? Thanks!


There is enough drag in the system from fluid circulation and friction to allow wheelspin at low speeds when the vehicle is off the ground. The controller doesn't need to work for that result to be observable.

What does happen is that as soon as the input shaft is spinning fast enough to overcome that drag, the wheels stop spinning. This is a mirror image of what happened to me when I was troubleshooting my car, and the solution to that problem was the controller.

You should replace the filter with the fluid every 40k miles. The fluid itself should be done every 20k, if we're sticking to the factory recommendation. This was mentioned by at least two people at the start of this thread and it should have been taken care of as one of the first things you did. You can theoretically replace the filter without draining the Haldex but the whole idea is to do both things at the same time so that that isn't an issue.

VCDS is made by RossTech and should always be purchased through him. You need a laptop/tablet with a full size USB port and a dongle that works with our cars. You can find the connectors on ebay for cheap ($5-10) but you should buy the software from the source. You can get a lite version (good for one install and one reinstall if you change machines) for $90, or at least that's how much it was when I checked last.


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## Christian_02_225 (Sep 20, 2016)

Okay, and when I do the filter change do I need to get another bottle of fluid? I literally just put in a new bottle last night but without a filter change. Can the filters be cleaned possibly? I mean I have a filter on the new unit I bought and thought that i could maybe salvage that one just enough to test the system in my car. My local VW dealership does not sell the filters so I would have to order one. So in the meantime I could at least try right? and would it hurt the other controller if I installed it with the clogged filter? Thanks


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## hunTTsvegas (Aug 27, 2012)

Regardless, do yourself a favor and either purchase Ross-Tech VCDS or something comparable. Regular code readers won't see all of the additional details that this software gives you. An example so you understand: if I hook up my car, I can click on each module that has a controller (i.e. engine, brakes, haldex, etc). Once in there, I have many different options such as reading codes, checking readiness or even performing output tests. Output tests are great for activating components that should be actively working in certain situations. Not only will it show absolutely anything to help with diagnosis but the company also provides excellent support through things like their Trouble Code Wiki, which has almost every VW/Audi trouble code, typical effects observed, and potential courses of actions to correct the code. I know I might sound like a fanboy but this single tool, though expensive, took my ability to troubleshoot/diagnose vehicle problems to a whole new level. I've used it to help other VW/Audi owners fix their vehicles as well, for no money of course.

If you'd still rather not spend that money, that's fine however you should use thisLocator to find someone in your area or close-ish. I can't speak for any others but if you were close to me, I'd be over to do a scan and offer any advice I can. Others may want a small fee, which is up to you to decide if it's reasonable. My advice would be to perform one of these two things before throwing anything else at it because the more you change, the more potential for troubleshooting error. You could swap that entire rear end and the issue could be a bad signal voltage or an ESP error causing the issue. Mine right now is a Lateral Accelerometer causing an ESP code. I wouldn't have known that had it not been for VCDS. 

Best of luck! :beer: (<----- you mention school and your general sentence structure implies to me that you're on the young side so think of that as a cream soda)


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## hunTTsvegas (Aug 27, 2012)

Christian_02_225 said:


> Okay, and when I do the filter change do I need to get another bottle of fluid? I literally just put in a new bottle last night but without a filter change. Can the filters be cleaned possibly? I mean I have a filter on the new unit I bought and thought that i could maybe salvage that one just enough to test the system in my car. My local VW dealership does not sell the filters so I would have to order one. So in the meantime I could at least try right? and would it hurt the other controller if I installed it with the clogged filter? Thanks


Filters can't be cleaned. Don't re-use one off of a salvage rear end as it has the probability of having more miles on it than the one on your car. If you have a way to get the drained fluid back in there, then reuse it but I would suggest using either a filter medium or cheese cloth to get any particulate out of the fluid when you drain it. This will also help you determine if there are pieces of the clutch pack in the fluid suggesting part failure. Win win!


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## Christian_02_225 (Sep 20, 2016)

I will have to look into that! I would also like to activate stuff like the one click door unlock, and other miscellaneous things. It is also always nice to be prepared at all times too. And YES I would love a cream soda right now lol.


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## Christian_02_225 (Sep 20, 2016)

I have no idea if anyone is actually going to see this post since it is so old but I finally bought a vag scanner and was shocked to see what came up when I scanned the AWD module. There was a total if 2 codes, The first one was 00526 Brake Light Switch-F sporadic: Implausible signal, the other one was 01155 Clutch sporadic: Mechanical fault, but when I cleared the codes, the 01155 didn't come back but the brake light switch code did. I recently replaced the sensor back last summer because my brake lights and cruise weren't working. The brake lights and cruise control work right now and I really don't know why it is throwing a code if it is working. I feel really stupid for not scanning my car before AS YOU GUYS TOLD ME lol. Tell me what you guys think, and look at my other thread on Cool things to do with Vag Com. Thanks


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> I have no idea if anyone is actually going to see this post since it is so old but I finally bought a vag scanner and was shocked to see what came up when I scanned the AWD module. There was a total if 2 codes, The first one was 00526 Brake Light Switch-F sporadic: Implausible signal, the other one was 01155 Clutch sporadic: Mechanical fault, but when I cleared the codes, the 01155 didn't come back but the brake light switch code did. I recently replaced the sensor back last summer because my brake lights and cruise weren't working. The brake lights and cruise control work right now and I really don't know why it is throwing a code if it is working. I feel really stupid for not scanning my car before AS YOU GUYS TOLD ME lol. Tell me what you guys think, and look at my other thread on Cool things to do with Vag Com. Thanks


Many of our cars occasionally throw the brake light switch code even when everything is working correctly. It shouldn't affect the operation of anything negatively.


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## Christian_02_225 (Sep 20, 2016)

Hmmmmm, well then why do you think that it would throw a code under the AWD module? I did the self-test and I could hear it faintly engaging every time it would cycle so I guess it is mechanically in order. I heard that these particular brake light switches were very bad and always failed.


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## asiwa (Dec 18, 2014)

Christian_02_225 said:


> Hmmmmm, well then why do you think that it would throw a code under the AWD module? I did the self-test and I could hear it faintly engaging every time it would cycle so I guess it is mechanically in order. I heard that these particular brake light switches were very bad and always failed.


Those brake switches are unreliable as all get out. I replaced mine twice in three years of ownership of my car.

The only thing the AWD test can do for you is confirm if your precharge pump is working. I always felt it was a generally unreliable way of testing the functionality of the Haldex as a whole. 

The software won't really tell you what is and isn't working unless you unbolt the controller from the car, in which case you will be able to hear a very audible whining noise from the stepper motor inside if it's functioning correctly. That requires you to completely empty and refill the coupling though and requires a replacement crush gasket for the controller when you bolt it back on. 

I previously had an intermittent mechanical fault and the issue ended up being the controller itself. The module can throw codes but some codes can have multiple causes. The troubleshooting continues!


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## bwdz (Jan 21, 2015)

Couple of things here. First, order the crush gasket from ECS or your local dealer. The dealer will tell you that there is no gasket as their screens don't show it but if you give them the part # which you can find online they can get it for you.
Second, my controller also failed. After replacing it with a good used one I took the old one apart and found the stepper motor to be stuck, after twisting on the gear with a pair of pliers it freed up and if reassembled should function again. They say that these controllers almost never fail, I think they do but it seems like just the stepper motor gets jammed. If your controller is acting up order the gasket and fluid and remove it, open it and see if the stepper motor wants to turn with your fingers. You might be able to just push on the rod in the opening to get it to free up without opening the controller and have yourself a cheap fix.


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## Christian_02_225 (Sep 20, 2016)

*Haldex REPLY*

Okay, back to this thread. I took the car to the local 1/8th mile drag strip this weekend and was only able to get 3 runs in because it was so packed. I raced a 180 TT and completely beat him both times by several car lengths. The track had very good bite and with that, I had TONS of wheel hop on the launch. Not a serious amount of wheel spin off the line but I only had the 2-Step set at 3000RPMs. I ended up running a 9.6 as my best time, I think I could get a 9.4 if I had more time to practice. Otherwise, the car performed flawlessly. The coolant temps never even went over 199 even while idling in the big line. I'm not trying to break the car but I try to keep it safe when running it. I shifted right at 6k every time since peak power is right before that and did not want to over rev the car of course. 

Anyway, back to the thread, this brake light switch code is now affecting other areas of the car, such as the cruise control rarely works anymore and the code now shows up in the engine module on the VAG COM, it only started recently. So I have the 00526 Brake Light Switch-F sporadic: Implausible signal in both the AWD module and the Engine module. Also, the AWD module shows the 01155 Clutch sporadic: Mechanical fault code. They all come back after cleared. 

I am going to open up my old controller as suggested to see if there is anything unusual inside. Also, when doing the self test, there is the QUIETEST click when I first click the test but when it engages and disengages the pumps and everything, I can't hear anything (noticeable anyway). 

Thanks for the advice.


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## Christian_02_225 (Sep 20, 2016)

Okay so I doubt anybody will even see this but I figured I would give a 2 year later update haha! So since two years has gone by, YES I still have the TT along with a Manual 335xi Coupe! Since the TT doesn't get driven as much, I finally decided to get the triple square bits I needed and went ahead and swapped the whole rear differential assembly with the haldex coupling. By the power of the Lord High Above, I OFFICIALLY HAVE WORKING QUATTRO!!! Doing the rear diff took about 6 hours taking my time and it was well worth making the AWD working after so long! Thanks again


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## tt92103 (Nov 23, 2010)

How do you know that your Haldex is working? Does it drive differently?
I'm asking because I have had my TT for 9 years and I only use it to commute to work and I live in a desert where it rarely rains and never snows. 
With all of the posts I read about peoples Haldex failing, makes me wonder if mine is functioning, maybe I would not know if it wasn't functioning???
It is supposed to rain in 2 days, I think I will try to find a patch of wet grass and hit the gas pedal hard and see what happens...


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## asiwa (Dec 18, 2014)

tt92103 said:


> How do you know that your Haldex is working? Does it drive differently?
> I'm asking because I have had my TT for 9 years and I only use it to commute to work and I live in a desert where it rarely rains and never snows.
> With all of the posts I read about peoples Haldex failing, makes me wonder if mine is functioning, maybe I would not know if it wasn't functioning???
> It is supposed to rain in 2 days, I think I will try to find a patch of wet grass and hit the gas pedal hard and see what happens...


You'll know if you try to pull away hard in the rain. If you go for a hard launch you should spin the wheels in the wet, especially with the slick roads down where you are.

Sent from my Pixel 2 XL using Tapatalk


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## Christian_02_225 (Sep 20, 2016)

So I knew mine was not functioning properly because even on a dry road, I could floor it in first gear and the tires would just spin..... In the rain it will be super easy to tell if it is working or not, mine used to spin like crazy in the rain, now it does not! I can NOW floor it in first gear in the rain without any noticeable wheel spin!!

To add: I have a N2MB WOTBOX installed (a standalone 2 step launch control/No lift shift module... it simply wires into the pedal switches and ignition wires) and on the first drive after I replaced the rear diff/haldex assembly, I attempted a launch.... that's when definitely could tell the haldex was doing something when my glovebox door flew open upon launching it! 

If you find evidence that your haldex is in not working, CHECK YOUR PRECHARGE PUMP first before buying a new assembly like I did. Also of course the basics like the ground strap, fuse, and any obvious wiring issues visually.


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## B1-16V (Aug 5, 2002)

Yep, my car's issue was the charge pump. I've got AWD now, but unfortunately it is on all the time. Parking lots and tight turns are awful. (binding). I'll have to tear into my controller soon I suppose.


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## tt92103 (Nov 23, 2010)

It rained, I went out and found some wet soaked grass and drove up on it, and I tried to accelerate fast. The car shuddered and the yellow triangle Traction Control warning light flashed a few times, but the tires didn't spin out. 
So I guess that means my Haldex is working?!? I have been good about changing the Haldex oil and filter, even though I didn't even know if it was functioning, lol.


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## Christian_02_225 (Sep 20, 2016)

This is a youtube link to a video showing the functionality of the Haldex system on my car. You can really see the rear wheels kick in when the fronts slip. Feel free to watch!
And the bang you hear is just the 2-Step function (WOTBOX)


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## Christian_02_225 (Sep 20, 2016)

tt92103 said:


> It rained, I went out and found some wet soaked grass and drove up on it, and I tried to accelerate fast. The car shuddered and the yellow triangle Traction Control warning light flashed a few times, but the tires didn't spin out.
> So I guess that means my Haldex is working?!? I have been good about changing the Haldex oil and filter, even though I didn't even know if it was functioning, lol.


It's honestly hard to say. Now that my haldex is operating, even on the dirt (in the video) my car hooks and pulls hard even from a launch on 2 step. Before my haldex was working, I could disable the ESP and spin through first gear even on pavement.


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