# P2181 - performance malfunction in cooling system... HELP!



## dave13s4 (Dec 16, 2004)

VAG-COM Version: Release 311.2-N
Control Module Part Number: 022 906 032 EG 
Component and/or Version: MOTRONIC ME7.1.1G 5626
Software Coding: 0000132
Work Shop Code: WSC 12599
1 Fault Found:
18613 - Performance Malfunction in Cooling System
P2181 - 008 - Implausible Signal
now the car is/was under warranty. i took the car in the first time, they replaced the CTS, gave me back the car, car was fine, few days later, light came back on, same code. took the car back again, they replaced the water pump and thermostat and thrmostat housing, they said the water pump impeller broke and damaged the thermostat. well they give me back the car, car seemed fine, then i noticed a day later that on cold start there was no elevated idle, thought to myself, the cel is gonna come back on, sure enough it came back on







. took it in again last night, they looked at it this morning and said the code came up, but when they tried to go through guided fault finding, that they couldn't find any causes for the cel. so they cleared the code, drove it for 36 miles to see if the cel would come back on, nothing, tell me to pick up the car, that they couldn't find anything. now i checked my fans before i dropped of the car last night and they were working, so idk what the problem is. here is where it gets tricky, i brought the car in last night with 49,968 miles, they give me back the car with 50,004 miles, now im out of warranty. i asked them if the cel comes back up and i bring it back if they are goin to warranty the problem, they said if its something wrong with the parts they replaced yes i have a warranty on them for 1yr/12k miles, if its something else causing it then no. i said well wouldn't u have to cover it since its a pre-existing problem, they said no, so instead of fighting i called VWOA and documented the problem, so if it happens, they should take care of me and cover it. so im gonna wait and see what happens in the next few days, i have a feeling that its going to come on again cause when i picked up the car it was cold, and there was no elevated idle. 
does anyone have any idea what the problem could be? i don't think its the fans cause like i said they seemed to be working fine.



_Modified by dave13s4 at 6:31 PM 12-12-2007_


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## dave13s4 (Dec 16, 2004)

*Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)*

BUMP


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## Ted Brogan (Dec 13, 2005)

*Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)*


_Quote, originally posted by *dave13s4* »_BUMP

have them check the coolant with a refractometer(not sure if i spelled that right) not a hrydrometer. If over the course of the vehicles life it has been topped off with straight coolant or improperly mixed coolant the mixture is probably not right. Have them add some water to it to get the mixture for about -25 as i bet you its sitting somewhere between -40 and -50 right now which is way to much. 
hope you get it sorted out let me know what they find

Tommy


_Modified by Ted Brogan at 10:40 PM 12-18-2007_


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## speedybunny2 (Nov 13, 2007)

vehicle needs a thermostat so throw one in there and clear the faults problem fixed


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## dave13s4 (Dec 16, 2004)

*Re: (speedybunny2)*


_Quote, originally posted by *speedybunny2* »_vehicle needs a thermostat so throw one in there and clear the faults problem fixed


read all the way through next time, the thermostat has already been replaced, along with the housing, water pump, and coolant temp sensor.


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## dave13s4 (Dec 16, 2004)

*Re: P2181 - performance malfunction in cooling system... HELP! (Ted Brogan)*

i mentioned that to them, and they said the mixture was fine, and then told me that they spoke to vw's tech line, and they said the cause of my problem is my cold air intake, so the dealership told me to put the stock airbox on and that would fix the car. i argued that fact but said fine, ill put it back on for u, just to prove to u that the light will come back on and that ur wrong. well i took the car home on wed night, and sure enough the light came back on this morning, so i can't wait to get in touch with them on wed. they're gonna hate me, cause this is the 5th time for the same problem, and now im done being nice and patient.


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## Ted Brogan (Dec 13, 2005)

*Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)*

Im sure they told you the mixture was fine, but i bet its not have them test it with you present so you can see the results yourself.


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## blackwolfjetta (May 3, 2007)

*Re: P2181 - performance malfunction in cooling system... HELP! (Ted Brogan)*

I'm having the same problem, came up last night on the way home. I was driving about 75-80mph and it came on. temp gauge said 190 but from what i've seen that is incorrect. The T-stat has been changed and the water pump went out at 47K. I'm at 57K now. That being said, I am not missing the belly pan. However, i have driven through snow and ice here in texas last Feb. and it didn't come on. S-T-R-A-N-G-E!
Will check mixture tonight, maybe santa will bring me the "meter"!


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## BlackBirdVQ (Dec 9, 2007)

*Re: P2181 - performance malfunction in cooling system... HELP! (blackwolfjetta)*

Bump this thread... I'm having the same problem here.
I replaced my black ECT with a new green ECT and cleared the code... took a while for it to come back - about 2 weeks or so. I thought it was some kinda fluke so I erased the code and kept my scanner in the car at all times. Cousin of mine who is a VW Tech mentioned to me that the coolant CAN throw the P2181 code.... so I flushed it out with a 50/50 VAG Coolant mixture. Light came back within 2 days....
Got me another green ECT and swapped it out on Friday right before I left work. Topped off coolant with pre-mixed 50/50 stuff and drove the car all weekend- 300 miles and today I decided to check the ECU, DTC pending- P2181. 
I know when the code comes back, the car looses power and feels sluggish on acceleration. When the light finally comes on, the car feels reallllly slow. So I carry my portable scanner with me at all times.
WTF ? 
Mods are GIAC chip, EVO CAI.
2 ECTs and coolant flush haven't fixed my problem. I love the car, I hate the check engine light !


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## R(ed)32 (Apr 1, 2004)

Another Bump! Same problem here. 
My Codes: 
18613 P2181 232
Malfunction in Cooling System
(2004 VW R32)
Have about 60K miles on it. ECT replaced last year. Monitoring temp while driving, it only gets up to about 175F to 180F on very cold days. The fault appears near the end of engine warmup, usually while on the highway for me. Problem is intermittant -- but it now seems like it's always going to occur on cold days. Haven't done any serious troubleshooting yet because of the lack of available information. 
Guess I'll check my fans (operating), then consider replacing the thermostat. Before going for the thermosat, however, I'd like to know what engine temps you folks see when warmed up and monitoring with a Vag-Com or equivalent system.
Thanks,
George


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## vdub_jetta (Nov 1, 2003)

*Re: (R(ed)32)*

had this same code last month. if it's not the water pump, tstat (as it was with me), or the green top, the last thing it could be are fault cooling fans.


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## Zba (Jan 1, 2002)

*Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)*

If one of the impeller blades is still in the cooling system, it could be getting caught on the t-stat keeping it from opening or closing all the way. The ECU will see that the coolant temp is not where it should be based on other inputs and throw a code. If the VW shop is flat rate, there is a good possibility that they did not flush the cooling system to get rid of any water pump debris. Just a thought. Good luck to you, and remember, the sqeaky wheel gets the grease


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## Ted Brogan (Dec 13, 2005)

*Re: P2181 - performance malfunction in cooling system... HELP! (Zba)*

Im gonna stick with my original statement. Ive found lately on these cars that they have become very sensative to coolant mixture. 50/50 is to much coolant ive been doing about 60/40 with will protect it to about -25 and it takes car of the code on every single car....
Trust me on this one properly check the mixture with the correct tools set it to what i suggest and see what happens.


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## R(ed)32 (Apr 1, 2004)

*Re: P2181 - performance malfunction in cooling system... HELP! (Ted Brogan)*

You may be right, Ted, about the antifreeze mixture causing a problem, but do you have any ideas about how or why that would trigger the computer to report a P2181 fault? 
George
ps -- I did observe both my cooling fans come on during a long idle in the garage so I wouldn't think that is causing a P2181 fault in my case.


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## Ted Brogan (Dec 13, 2005)

*Re: P2181 - performance malfunction in cooling system... HELP! (R(ed)32)*


_Quote, originally posted by *R(ed)32* »_You may be right, Ted, about the antifreeze mixture causing a problem, but do you have any ideas about how or why that would trigger the computer to report a P2181 fault? 
George
ps -- I did observe both my cooling fans come on during a long idle in the garage so I wouldn't think that is causing a P2181 fault in my case.

Honestly i have no technical explanation as to why it causes it but for some reason it does lol.


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## modulation (Nov 6, 2006)

*Re: (R(ed)32)*


_Quote, originally posted by *R(ed)32* »_but it now seems like it's always going to occur on cold days. Haven't done any serious troubleshooting yet because of the lack of available information. 
Guess I'll check my fans (operating), then consider replacing the thermostat. 

I have this same issue and I think it's the cooling fans.
If it only happens on cold days is that because you have the AC off on those days and ON when it's not a cold day?
My fans appear to function fine with the AC on @ idle.
However they don't appear to turn on to their low speed mode when they should (when the coolant reaches ~85-90 degrees c.) They kick on when the coolant temp reaches >100 degrees c but kick right off again when the car is <100 that's the high speed mode.
I'm not sure what is causing this problem though.


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## R(ed)32 (Apr 1, 2004)

*Re: (modulation)*

Interesting link you posted in the R32 forum a few days ago regarding the high and low speed functions of the cooling fans. I know both my fans came on when idling in my garage, but I don't really know if it was slow or fast speed. Possibly fast only -- will have to check this out again with the a/c running. 
My understanding is that the fan will come on (apparently in low speed) whenever the a/c compressor is run, and only go to high speed based on coolant temperature. If this is correct, I might have a low speed fan failure and that fault could be the possible source for the P2181 code.
George


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## blueduece (Sep 11, 2007)

*Re: (R(ed)32)*

had same code took it to the dealer and they replaced the coolant temp sensor and now all is well


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## 20aeman (Jun 8, 2006)

In all likelyhood its the coolant temp sensor. I actually had the code pop up, replaced the cts and nothing. So a month later, decided to replace the cts again just for the hell of it and viola, it worked. No more cel.


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## xsp2467 (Oct 13, 2004)

*Re: (20aeman)*

This is an interesting problem, i have it as well P2181 Coolant Performance Malfunction. I have already replaced the coolant temp sensor, and the CEL went away for a week and a half, but its back on now. I've been talking to my guys at the dealer and they told me to replace the thermostat next, but before I do that i think im gonna replace the thermoswitch first clear the code and see what happens, after that if it comes back then ill go for the thermostat, I have observed that fans comming on at different intervals and temperatures so the thermoswitch might have a lot to do with it.....ill keep you guys posted.
Bump for a good thread http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## R(ed)32 (Apr 1, 2004)

It seems that in warmer weather, I'm not getting the P2181 code any more. Haven't replaced any parts or adjusted coolant level to change that. ???
Have confirmed that my low speed fans are not working. Fuses are okay, fast speed works, so I'm assuming that the low speed resistors in the fan motor assemblys are shot. (My digital volt meter has died, so no measurements there yet.)
I think this is a big problem -- on a long highway drive, I got held up in stalled traffic several times. On a 66F day, after about 10 minutes idling along, my high speed fans would energize. Plugged into the OBD computer to see what was happening and found that coolant temp was cycling between about 222F and 226F with an occasional spike to 230F. (This was with the A/C off.) Can't have that happening in hot weather! Ordered two of those power resistors that I'll mount externally to restore low speed fans.
George
p.s. At highway speeds with no fans, my coolant temp was pretty steady at about 184F.


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## kbs3 (Dec 23, 2001)

*Re: (R(ed)32)*

I am having the same code p2181. I sat at the lower woodlands park today and let my car idle. I then tried to make my fan come on? I turned on the A/c and still no fan? What tells the fans to engerize? i checked the fuse and it looks alright.


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## R(ed)32 (Apr 1, 2004)

*Re: (kbs3)*

The way I understand it -- 
The low speed fan will come on whenever the a/c is switched on regardless of temperature. Or it will switch on between about 198F and 206F, even if a/c is off. This is controlled by a thermoswitch. 
The hi speed fan will switch on between 210F and 221F, also controlled by the thermoswitch. The fan controller deenergizes the low speed circuit when high speed is switched on. 
The most probable failure you have is an open circuit in the power resistor inside each of the two fan motors. That will prevent low speed fans from running. If you are at operating temperature, and idling a while however, your high speed fans should kick in when coolant temp reaches the thermoswitch setpoint. (That's good, but, if you drive like that in hot weather, you'd better not use your a/c if you have to spend any time stopped or very slow. Some people have said that it's not good to run that a/c compressor without fan airflow around it.)
If it's the low speed resistors burned out, and you're still under warranty, get VW to replace both fans. A couple weeks ago, I used the DIY method and installed two 1 Ohm/100 watt external power resistors on an aluminum plate for a heat sink. This restores low speed fans, and it will probably last a lot longer than two new fans, believe it or not. 
Finally, I have never seen any proof that the p2181 code is related to the cooling fans. Could be, but ? ? ? ? A month or two before I fixed my fans, I stopped getting the P2181. Didn't do anything to fix it. I think there's probably something not quite right about my system, but it only showed up during cold weather warmups for me. 
p.s. When the fans come on in hi speed, they're plenty loud enough -- you'll hear them from inside the car. Low speed is pretty quiet -- you'll probably have to raise the hood and look to see if they're spinning.


_Modified by R(ed)32 at 11:20 PM 5-28-2008_


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## kbs3 (Dec 23, 2001)

*Re: (R(ed)32)*

so get this... tonight i start my car with the radiator cap off. try to see if i can burp so air bubbles. now my car fluctuates a little bit from 185-190 degrees instead of just sitting at 190 all the time. i also sat there and let it heat up to 190 and still no fans. The damn thing won't over heat either.it just idles along and stays at 190 degrees. i also saw the fans turn on with the a/c so i know at least part of the system works. i am more lost then ever. i am thinking of just getting a new time belt, metal propelled water pump and whatever else and just living with it on my credit card...


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## R(ed)32 (Apr 1, 2004)

*Re: (kbs3)*

In an earlier post I mentioned that when stalled in traffic, my actual temperature monitored via OBD went up to 230F. The dashboard temp gage needle never left 190F. That gage doesn't reflect accurate coolant temperature. It's more of an idiot light and not useful to show you what's really going on.


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## vwemporium (May 27, 2002)

*Re: (R(ed)32)*

Hello 
This is so true about the gage being an idiot light.
If you need help give me a call. I specialize in these cars.
I'm in Montgomery NY.
Best,
Jack
email 
[email protected]


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## kbs3 (Dec 23, 2001)

*Re: (vwemporium)*

i noticed 2 things today about my car...
1. even at 190 degrees on my dummy light, there is almost no pressure in the reserve reservoir and it never boils over
2. The fans never turn on. When the a/c is active sometimes only the small fan is turning.


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## xsp2467 (Oct 13, 2004)

*Re: (kbs3)*

I noticed that my fans dont come on until the engine is at the high temp, im not exactly sure but i thought that they were suposed to go on the low setting when the a/c was on


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## rowdyzombie (Jan 18, 2001)

*both ac fans are to come on when ac is on.*

Well, both big and small fan are supposed to go on when a/c is on (low setting). I tested mine and only small fan was on, so replaced big fan and both are working now.


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## kbs3 (Dec 23, 2001)

*Re: both ac fans are to come on when ac is on. (rowdyzombie)*


_Quote, originally posted by *rowdyzombie* »_Well, both big and small fan are supposed to go on when a/c is on (low setting). I tested mine and only small fan was on, so replaced big fan and both are working now. 

I have heard so many mixed reviews about the fan's spinning. Some say low speed setting in only the passenger side fan. Some say that both fans should spin.
I have seen both of my fans run before. Then sometimes only the small fan.
I have a new theory about the p2181 code. I noticed when i took out my last green top sensor that it has no o-ring gasket. I am curios if some of the pressure is escaping due to the fact?


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## R(ed)32 (Apr 1, 2004)

*Re: both ac fans are to come on when ac is on. (kbs3)*

both fans ALWAYS switch together. if one is running in either low or hi speed, and the other is not, the one that's not running is broke. if neither fan is running in low speed with a/c on, they're both broke. 
if you're using a/c in hot weather, and your low speed fans don't run, your a/c compressor may be at risk. 
if you get stalled in traffic on a hot day, and your low speed fans don't work, be very careful. if your high speed fans don't come on, you should stay in your driveway, or stay on the highway and never stop!


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## xsp2467 (Oct 13, 2004)

*Re: both ac fans are to come on when ac is on. (R(ed)32)*

Thats good to know, ill have to get the vag com and heat test the car and graph the warm up process and log when the fans come on. As for the o-ring, I just replaced the greeen sensor with another green sensor, both of the sensors had their o-rings.


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## Mike Solo (Jan 26, 2005)

*Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)*

Back from the dead. I threw this code a few weeks ago, driving down the freeway at about 70 mph.
Cooling fans are working properly.
Water pump is functioning properly.
Green-top coolant sensor installed.
If there is nothing else to check, I'll flush the coolant & replace the thermostat, and hope that covers it. Just wondering if anyone found anything else.


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## jimix (Jul 21, 2003)

*Re: P2181 - performance malfunction in cooling system... HELP! (Mike Solo)*


_Quote, originally posted by *Mike Solo* »_...
If there is nothing else to check, I'll flush the coolant & replace the thermostat, and hope that covers it. Just wondering if anyone found anything else.

Did flushing the coolant work for you? 
I've got this code too. Have already replaced the sensor 3 times, thermostat, and water pump.


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## sveda (Apr 18, 2001)

*Re: P2181 - performance malfunction in cooling system... HELP! (dave13s4)*

Mine started this last spring on cold mornings, after doing 70 mph on the highway for a few minutes I get a CEL. Error code P2181.
Errors went away over the warm summer months, but came back in the cool fall weather. I parked the car for most of the winter, but I'm still getting Error code P2181. Coolant topped off, lots of heater output, no overheating, fans working, new coolant temp sensor...
Any insight is greatly appreciated.


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## imcginnis (Apr 2, 2010)

You should check the freeze frame data for when the fault is setting, instead of just throwing every part in the cooling system at it.


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## BillR123 (Mar 17, 2012)

A problem with the probe sensors in the coolant tank IS a sensitivity to the coolant fluid's electrical resistance (Ohms) and if not just right, your car will throw P2181 codes. As has been stated, don't use an excess of antifreeze (as suggested, 60% water and 40% antifreeze is a good mix). Also don't use "purified" water, use only the stuff that comes out of the water hose and hopefully there's enough mineral content in your water to maintain an operating fluid resistance level. 

As suggested, check your coolant mix ... you might have too much coolant ... my 2003 Audi TT had too much antifreeze at 35K miles. If someone added "purified" water to your coolant mix, then you're really screwed. 

If your handy with a digital voltmeter, measure the before and after resistance of the coolant tank solution at the tanks connector ... with the cable connector removed. Hopefully note a lower resistance. 

And if your P2181 codes occur at specific street locations, that's because a nearby radio transmitting device is affecting the coolant tank sensing circuitry. Radio signals are introducing a signal voltage on the coolant probe cable going to the ECU. So the solution to the problem is (1) use more water with minerals, (2) use less antifreeze, (3) use a grounded, braided shield over the sensing wire. 

Application of silicone insulating grease on the coolant tank's probe connector pins would help with this "dry" circuit. "Dry" circuit refers to a circuit with very little electrical current, causing connector contacts to become more easily contaminated. Therefore, not assuring a good, electrical contact for "dry" circuit conditions.


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## Barn01 (Feb 26, 2011)

Great 1st post BillR123 

I have been plagued with this error on and off for the past 6 months and had the water pump changed (with timing belt), and the sensor. When I go back in time I did go to mr Lube and have them change the fluid. I remember they put in the green stuff and flushed out the high mileage red stuff. I told the dealer and they said that's fine. It was shortly after this fluid change I recall that the problem with my CEL and coolant gauge dropping to C, yet it still blew hot air even at -30C outside. 

I was just about to pay and have the tstat changed but I think I'm better off to change the conductivity of the coolant. Do you know approx the value I should read off the sensor? Also what kind of tolerance in that value I might have?


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## steveppd (Aug 10, 2011)

First check ECT sensor resistance, if its within spec let car cold soak then take on test drive. Use your scan tool to monitor temperature and check to see if the car gets up to 175ish degrees within a few minutes. Average speed must be over 6mph to trip the light so keep it up over that. If car is to slow to reach operating temperature, 2181 will set. 99% of the time its been the thermostat. 



Resistance should be between 

Min Ohms Max Ohms Temp F 
5000 6500 32 
1500 2000 86 
500 650 140 
275 375 176 
200 300 194 

Trouble code 18613 (P2181) indicates the cooling system is not reaching operating temperature quickly enough. 

1. With the engine at 68 degrees F. under normal driving conditions 175 degrees F or more should be indicated after about 4 to 5 minutes of driving. 

2. If the engine is not reaching operating temperature quickly enough, a faulty thermostat is usually the cause of the slow warm up condition. 

3. Check for poor or corroded connections at the Coolant Temperature Sensor (CTS) as well. 

I hope this helps.


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## jedi kyle (Aug 22, 2011)

*i hate this light as well*

i have just replaced the sensor with the green one and when i bought the car i had to replace the radiator fan. and i also replaced the coolant res. not because i thought it would have been a problem but it broke. 
i have a VF stage 2 super charger on the car i don't think that should have any problem. i find the problem only comes with cold starts or if you don't let it idle for at least 5 mins in the morning. i know its inconvenient.but you should do it every day any way.


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## Barn01 (Feb 26, 2011)

I just wanted to update this thread to say that I was wrong!!

It wasn't the coolant. I tried swapping out the green and replacing with G12 and the Code came back. Also the sensor was replace but the code came back after a day.

So on the weekend I bit the bullet and replaced the thermostat. What a PITA job on my A3 but in the end everything is working fine now and temp sits perfectly in the middle of the gauge.

There are lots of tips I could give someone that wants to do this. So if any of you want to change this part be aware it's not fast or easy. If you don't like getting your hands dirty and don't have patients then just take it to the dealer haha.


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## DBVeeDB (Aug 3, 2007)

Bumping this thread - As I am trying to figure out what to try next. 

2005 Audi TT 3.2 (DSG) - Car has been experiencing long warm up times. In 55*F weather, it took the car 20min at idle to reach temp. I did the same test on a friend's r32, it took his car roughly 7-8 minutes (Same day, cars were next to one another). On a colder day like today, around 25-30*F, it took over 20min of DRIVING to get to temp. This is the same for warmer weather as well, just marginally worse on colder days. The car is garage kept, so 50-65 ambient temp in the garage, not an ice cold motor. Soft code P2181 registered via VCDS but I didnt check freeze frame data. 

I have had this issue for about 16-18months, it has persisted regardless of the following repairs done in that time since first observing this code and slow warm up times. 


Greentop CTS (on my 3rd OEM unit now)
OEM 80*C Thermostat (on my 2nd one of these just to rule it out)
50/50 G12 mix with distilled water. Always changed with every job.
New OEM Audi Fan Control module
New Fans
New Radiator
New Reservoir/Globe
Wiring on connector of CTS looks good
Resistance checks out on CTS itself when cold (haven't tested this when running, not sure how?)
Rebuilt Gauge cluster
Replaced 1-way valve located in hose between aux pump and DSG cooler. One that was removed was not stuck though

So, I don't think its my thermostat, I don't think its my sensors. Reading the above posts im inclined to start a new mixture of 60/40, reducing the antifreeze content. I also discovered there is another 1-way valve on a different hose that also leads to the DSG cooler (didn't realize there were two of these). So I will also replace that. Last idea will be to check wiring to the CTS and near ECU for any damage or migration. But the heat does not return hot air until after it gets to temp, so I dont think I have a sensor or bad signal. I seem to be experiencing a true slow warm up. 

I have seen a few 2.0T DSG threads turn up citing those one-way valves for causing under heating, its the only thing that makes sense to me based off everything I have tried. What else could cause a car to not warm up? Fans being on? (they are not) poor tuning? Over-efficient cooling? (I have the CSF radiator, and an A/C delete, but this shouldn't matter if the Tstat is indeed closed during warm up.)

SOS!


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## DBVeeDB (Aug 3, 2007)

DBVeeDB said:


> I also discovered there is another 1-way valve on a different hose that also leads to the DSG cooler (didn't realize there were two of these). So I will also replace that. Last idea will be to check wiring to the CTS and near ECU for any damage or migration. But the heat does not return hot air until after it gets to temp, so I dont think I have a sensor or bad signal. I seem to be experiencing a true slow warm up.
> 
> I have seen a few 2.0T DSG threads turn up citing those one-way valves for causing under heating, its the only thing that makes sense to me based off everything I have tried.


Bump for anyone who encounters this thread - I removed the cooling hose that ran from the AUX pump to the DSG Cooler, and sure enough the 1-way valve was stuck open, allowing flow in both directions. Looking at the cooling diagrams, this technically allowed for some thermostat bypass to the rest of the cooling system, likely causing my underheating/slow warm up issue. The part # for this valve is 1J0-122-351. On a DSG TT 3.2 like mine, there are two of them. On other 3.2's there is just one between the lower rad hose and Aux pump, and this valve is usually included with the hose assembly from factory.


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