# Haldex problem and question



## bwdz (Jan 21, 2015)

So my TT has high miles (183k) and I've only had it a few months. Its a 225hp Quatro. For a while while turning sharp at low speeds I could feel the bucking as if the rear end was not disengaging. The AWD worked great when the snow fell here in Michigan a couple months ago but it seemed like it was not disengaging. Now it is not engaging at all, I only have FWD (tested on the snow with ESP on and off). I checked the fuse and it is fine. What is the next step?


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## Tempes_TT (Oct 24, 2010)

Often times, it happens to be a failed pump. But it can be that, or the controller and also the things youve mentioned above, of which youve already diagnosed. Thankfully, I personally havent had any issues with mine what so ever at 194,xxx.


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## asiwa (Dec 18, 2014)

Do you have VCDS available to you either through a friend or through a shop? If so you are best off checking out the Haldex control unit for fault codes. 

It (unfortunately) sounds like you are having the more serious bad clutch/binding diff problem that is associated with rear end failure. Without seeing the codes first there is no way to make a solid conclusion. You could just as easily have a control unit that has packed up and those can be had from a German scrapper for around $100.

First things first - get those codes looked at! 

Oh, and if you can get the car up in the air enough to climb underneath, check the rear diff for a corroded/missing ground strap. That's a fairly common issue especially on higher mileage cars that can be remedied for less than five bucks.

EDIT: While the car is in the air (make sure all four wheels are elevated  ) Run the car in first gear and have a friend check and see if all four wheels are turning. That is an easy diagnostic test if you don't have immediate access to VCDS.


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## bwdz (Jan 21, 2015)

What is VCDS? I have access to a hoist at a friend's gas station after hours. I have a OBD2 scanner but the only thing I can get from that is an occasional oxygen sensor code. I have read about the VAGCOM and would like to get one but would like to get it on a budget as I will only tinker with this car with it. Can anyone tell me which one to get that will have the software that would allow me to read all the codes without breaking the bank? I was not aware that the rear end can fail, assumed it had to do with the Haldex being suddenly disengaged. When the car would "bind" at slow turn speeds pulling up just one notch on the parking brake to disengage the Haldex would solve that (I did some reading on the Haldex and that was the simple test to see if it unlocks)


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## bwdz (Jan 21, 2015)

http://www.totalcardiagnostics.com/shop/vagcom-rosstech-vcds is this the one I should get? it looks like they're out of Australia


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## Converted2VW (Apr 8, 2009)

bwdz said:


> http://www.totalcardiagnostics.com/shop/vagcom-rosstech-vcds is this the one I should get? it looks like they're out of Australia


Damn that sounds like a too good to be true deal!
VAGCOM (aka VCDS, RossTech) cables are typically around $200+
If this one really works like they advertise it would be a total score. I have no experience with this though. I have RossTech's VCDS cable.


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## thormx353 (Dec 24, 2012)

bwdz said:


> http://www.totalcardiagnostics.com/shop/vagcom-rosstech-vcds is this the one I should get? it looks like they're out of Australia


Can anyone confirm this? There has to be something I'm missing. If it quacks like a duck....


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## thormx353 (Dec 24, 2012)

bwdz said:


> So my TT has high miles (183k) and I've only had it a few months. Its a 225hp Quatro. For a while while turning sharp at low speeds I could feel the bucking as if the rear end was not disengaging. The AWD worked great when the snow fell here in Michigan a couple months ago but it seemed like it was not disengaging. Now it is not engaging at all, I only have FWD (tested on the snow with ESP on and off). I checked the fuse and it is fine. What is the next step?


Also I have the same problem. Did have awd previously and now only have fwd. At 185k I'm thinking it the Haldex pump but will be checking from bad grounds since that solved other members issues before.


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## Converted2VW (Apr 8, 2009)

VCDS should give an error code if there's electronics issues with the haldex.
Also, when was the last time the Haldex was serviced? Our cars are supposed to be serviced every 20k miles


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## thormx353 (Dec 24, 2012)

Converted2VW said:


> VCDS should give an error code if there's electronics issues with the haldex.
> Also, when was the last time the Haldex was serviced? Our cars are supposed to be serviced every 20k miles


and you should probably change the trans and diff fluid as well if you do not know when the last time it was changed.


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## iBorg (Aug 20, 2014)

I've found some tutorials about changing the Haladex. I'm putting it off.

What's involved in the changing the transmission fluids? What are the recommended lubricants? (sorry don't think this is quite a thread jack).


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## bwdz (Jan 21, 2015)

I was going to order the filter and Haldex oil as I have no way of knowing when it was changed last but that doesn't really explains why it was somewhat malfunctioning before by staying on all the time and now not coming on at all. I will do the service when I figure out the problem but still looking for the problem.
I see that Vag Com is causing a stir for some reason, is the answer that it is the one I should get or not?


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## lite1979 (Sep 9, 2005)

Does the traction control light come on and stay on? Is the fuse good? I'm dealing with the binding right now, but it's pretty darn cold, and I don't have a lot of time to work on my car between work and running my small business.


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## 20v master (May 7, 2009)

No mention of ASR light at. Check the ground strap on the rear end. It can corrode and break, and cause you to lose Haldex. Can you hear the charge pump running with the key turned on? If not, you know the issue.


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## bwdz (Jan 21, 2015)

Traction control works properly, cuts throttle back when front wheels spin, light flashes when spinning but otherwise is not on. Where is the ground strap? what does it attach to? 
For the guy who has the binding problem try the car at low speed turning very tight and pull up the parking brake handle just one little notch so that the brake doesn't actually engage but the brake light on dash comes on. The Haldex clutch is supposed to kick off automatically when the parking brake light comes on.
I ordered a Vag Com and will get it next week. I'll have it on a hoist and check everything out at once.


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## 20v master (May 7, 2009)

bwdz said:


> Traction control works properly, cuts throttle back when front wheels spin, light flashes when spinning but otherwise is not on. Where is the ground strap? what does it attach to?


Please learn to use the search function of this site, or Google It's on the driver's side rear, and grounds the rear diff/Haldex to the body. 

It's the 3rd pic in google images in that link.


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## bwdz (Jan 21, 2015)

20v master said:


> Please learn to use the search function of this site, or Google It's on the driver's side rear, and grounds the rear diff/Haldex to the body.
> 
> It's the 3rd pic in google images in that link.


Thank you for the pic, I saw the pic above the axle but wasn't sure which side was pictured. I will look at it when I get back on a hoist.

As far as using the search function, well I have, for 2 months now I have been reading and searching as I like to know what I am doing on my car. It is a lot of dead ends and an awful lot of speculation without concrete answers. Im all for checking the obvious known failure points first (hitting the easy button) but I also appreciate answers from the knowledgeable people with an actual diagnostic procedure rather than a guess with throw a bunch of parts at it and see if it fixes it. I am pretty mechanical and wrenched before (20 years ago) but these days just tinker, however I don't like guessing. When I wrenched we always had to isolate a problem and see if we can make it go away and reoccur to pinpoint the exact part needing replacing. I have read very few posts in the 100s that I did read that actually proposed a proper diagnostic procedure. Sorry to have wasted anyone's time.


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## asiwa (Dec 18, 2014)

Sorry I'm so late to the reply on this one. I'll talk about each issue in order  

The binding problem you were experiencing can only be caused by a select few malfunctions. The first probable cause would be the Haldex controller itself. That control unit has a pressure regulating system in it that controls the pressure on the clutch plates in the Haldex coupling. When the control unit does not regulate that pressure correctly, or you have some other type of failure, you get binding in the rear end at low speeds and tight turning radii, or some other type of incorrect Haldex functionality.

I'm glad you mentioned the handbrake light switch functioning correctly; that switch can be a common failure point for your Haldex not working at all, similar to how it is acting right now.

In essence, that binding you were experiencing likely resulted from a bad controller. The only way to find out is with that VAGCOM you ordered (now formally called VCDS) and to read any potential fault codes that may have been stored.

Now to address the current issue - no Haldex at all.

A few people on here have already discussed the pre-charge pump. That pump is responsible for circulating the Haldex oil inside of the system so that the control unit can do its job more quickly with less lag time. That pump is prone to failure due to the nature of its small seals that keep oil from getting inside the internals. If that pump fails you get zero AWD. When you get your VCDS package, you'll be able to run the Haldex output test and be able to listen for the pump whirring on the underside of the car. With the key in the accessory position you should be able to hear it faintly from inside the cabin.

That pump COULD be the issue for your lack of Haldex. I would however be inclined to say otherwise as you were having another Haldex problem immediately before this happened that is unrelated to that pump. 



20v master said:


> No mention of ASR light at. Check the ground strap on the rear end. It can corrode and break, and cause you to lose Haldex. Can you hear the charge pump running with the key turned on? If not, you know the issue.


Not necessarily. The pump is supposed to have power above 400 or 500 RPM - can't remember which at the moment. I wasn't able to hear my pump with the key turned to accessory and thought my car was having an issue when the only way to actually hear the pump is to run the output test.

The other issue that a few have mentioned is your ESP/ASR/whatever acronym you prefer light. My car is an '01 and as such doesn't have the issues related to that system, but if your ESP/ABS lights come on and stay lit at any time you will likely have no Haldex. Those stability control/brake systems interact constantly with the Haldex computer and if either system fails the Haldex will go dormant. You did say though that your ESP is functioning correctly, so I doubt it is even an issue at all.


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