Hi All, looking for any information on best way to replace a suspected cracked T-Stat housing. I see where antifreeze has been dripping down the drivers side of the oil pan (after an overheating that pretty much emptied the coolant). I replaced the coolant, but it is draining out once I get it up to operating temp. If anyone has the correct procedure to remove and replace this, I would appreciate any advice, suggestions or documentation.

 

Just make sure you know where it's coming from; take off the bottom splash guards so you can see everything, and it shouldn't be difficult to tell where it's coming from with the car running. Protect your eyes. You can easily locate videos on how to remove/repair a leaking T-stat housing for this car...Google it...key words; the title of your post + video.

 

Thank you for the advice - yes, this observation was with the splash shield off. I will look for the video's as mentioned - the help videos I have found are either for older Audi/Porsche/VW's or newer Q7's. I will keep looking. Not sure if I have to remove the intake manifold to get to the T-Stat housing. Continuing the search and will update if I find answers/repairs.
Thanks!

 

Once you can eyeball the source of the leak; it'll become pretty obvious, and I did find videos for 2008 Q7, so go look that up for research.

 

Also make sure the leak is not from the "crack pipe" at the water pump end. That o-ring may be failing from overheating and the plastic could be disintegrating. Take a look from under to make sure, because you do not want to do only part of the work and find out it was the crack pipe that was leaking.

You can probably get to the thermostat housing and its 3 bolts without removing the intake manifold, but the space is going to be tight. I was doing the valve cover, and therefore had to remove the high pressure fuel rail and intake manifold. Some moron engineers decided in order to remove the manifold you had to take off the Bank 2 high pressure rail. Your 09 may already have the 2-piece manifold so the fuel rail part is not necessary.

My plastic "crack pipe" was failing at the water pump end, the plastic was disintegrating and the o-ring was bad. The thermostat was still working ok but it did fall apart opening the housing. Therefore I would replace it with a new one.

If you change the thermostat housing, gasket and the thermostat (highly recommended, around $60 for the genuine thing, I got mine when it was $40), you might as well replace the "crack pipe". This is a known failure part. Uro sells an aftermarket all-aluminum replacement for $59. Make sure you have all the gaskets (sold separately). The crackpipe has an additional plastic extension with the coolant temperature sensor seat, that would be a dealer part and might as well.

You can use an aftermarket temp sensor for about $6 on Rockauto: https://www.rockauto.com/en/moreinfo...t=4748&jsn=429

Replacing the crack pipe was quite some work with the manifold off (remove the alternator too, after disconnecting the battery under the seat), because of all the coolant hoses and clamps and the angles you had to hold the pliers. I imagine with the manifold in place that is going to be more challenging.

A metal solution to the plastic "crack pipe":
https://www.rockauto.com/en/moreinfo...=10337&jsn=384

For the amount of work involved, I would NOT use a $17 housing and thermostat kit like this: https://www.rockauto.com/en/moreinfo...=10337&jsn=382
You can get a Gates housing while ordering from Rockauto, and then a genuine thermostat and gasket from an online dealer (among other needed dealer parts):
https://www.rockauto.com/en/moreinfo...=10337&jsn=385
https://www.audiusaoemparts.com/oem-...tat-03h121113d

You can also check Touareg 3.6L thermostat and crack pipe replacement procedures:
See post #3 in the link: https://www.clubtouareg.com/threads/...cement.245073/
Picture of the crack pipe with the alternator removed. The 2nd picture shows the thermostat housing to the right of the oil dipstick tube: https://www.clubtouareg.com/threads/...g-leak.291974/

That being said, if you are absolutely sure the leak was only from the thermostat housing, and everything else looks fine, then that may be the only thing you want to replace. For my 07, I had to use a vacuum coolant fill tool (about $50 on Amazon for the budget ones), otherwise some air gets trapped in the system, and the radiator fan will run on high speed for a good while after shut off.

 

Thank you, Steelcoil for all of the information. I do appreciate the time you spent and will post a follow up once I get this resolved.
Cheers

 

I had exactly the same symptoms and it was darn hard to find the source of the leak. It turned out to be where the crack pipe enters the back of the water pump, I assume from skrinkage of the o-ring. It didn't leak when the engine was hot, only after driving and the engine cooled a bit while the cooling system still had pressure. It's darn near impossible to see the end of the crack pipe, and I found where it was leaking with a "snake" camera. There's one little path to see where the crack pipe enters the water pump by holding a mirror at just the right place behind the alternator and using a flashlight. It is difficult.

The service manual says to remove the alternator for access. I had the job done at an indy shop and the mechanic somehow got it done leaving the alternator in place. I had them replace all of the plastic parts and thermostat with OEM parts. Two years ago the parts cost was $320 (including full coolant replacement) and labor was $810, which would have been about 6 hours. (Audi's name for the crack pipe is thermostat housing, what others call thermostat housing Audi calls cover).).