# How To: Replace Thermostat Housing - 2.0 TFSI



## poder (Mar 18, 2015)

I replaced the thermostat housing on my 2006 2.0 TFSI (BWA engine). On this model it's not possible to change the thermostat only, but rather the whole housing has to be replaced.
This is not an easy job! There's not much room to work in and even though you start out in a Zen-like state of mind with unlimited patience, you're going to end up needing all your favorite swear words :lol:

Sorry the pictures are not great quality  I did change camera underways which helped a bit, but it was quite clouded and dark...
Not all steps are required to be in the described order and likely I forgot to mention some minor things, so don't start this thinking it's a no-brainer. Most likely you'll have to adjust the procedure slightly along the way...










Unfortunately the unit is located in a tight place on the side of the engine pointing towards the front of the car.

*Tools*
You'll need mostly basic tools but, also a 5 mm XZN (triple square) bit.

*The procedure&#8230;*

To gain access to the thermostat housing we need to remove some components, one of which is the alternator. For this reason we need to disconnect the battery (negative) earth.

1) In the boot, use a 10mm socket to loosen the battery negative wire









2) Put it to a side and make sure it won't touch the battery pole.









3) Put a rag or similar in the catch mechanism on the tailgate so it can't close - no power means your remote doesn't open the boot anymore ;-)









*Working underneath the car*
4) Remove the under tray
5) Unclip and remove the tube between the intercooler and the fixed pipe on the right hand side of the car. This will ease access to drain the coolant.









6) Drain the coolant into a suitable container by removing the clip and pulling off the hose connecting to the radiator. You may want to put something behind to avoid coolant splashes.









*Working from the top of the engine bay*

7) Remove the engine upper cover / air filter.
8.) Pull up the carbon canister and put to a side.









9) Mark the W-belt so that you can mount it the same way round again.
10) Use a 16 mm spanner to loosen the tensioner and insert a 4 mm drill (or something similar) in the hole to lock it.









11) Remove the W-belt
12) Undo the three bolts and remove the tensioner (23 Nm)
13) Undo the two bolts holding the alternator (23 Nm)
14) Take off the alternator plug along with the electrical wire and its holder and remove it completely.









15) Loosen the clips and pull off the hoses on the front metal coolant pipe.
16) Unscrew the single screw and remove the front metal coolant pipe completely.









17) Loosen the clip and pull off the hose from the topmost pipe on the thermostat housing.
18) Remove the screw holding the metal pipe to the front of the thermostat housing.









19) Remove the bolt holding the pipe at the other end. This is hidden behind some wires and very hard to see!
At this point I had started to remove a few other nuts, bolts and plugs that probably weren't necessary, just to find this bolt!









20) Put the inner metal coolant pipe as far to the gearbox side as possible.
21) Unclip and push/pull down the coolant hose connected to the bottom of the thermostat housing. This may require tapping with a screwdriver and hammer - look at the new thermostat housing on how it connects and where to safely tap.









22) Unscrew the two bolts holding the thermostat housing in place (15 Nm).
23) Put a rag under to catch any coolant left and pull out the thermostat housing.
24) Lubricate the O-ring on the new thermostat housing, using coolant.









25) Position the new housing in place. You may not be able to push it all the way in due to the friction of the new O-ring.
26) Put the two bolts back in and tighten them using just your fingers at first. If you have to pull the housing in using the bolts, be sure to switch between the two, to make many small increments so it goes straight in. 15 Nm torque.

27) Reassemble rest in reverse order.
28) Put back in the old coolant fluid or new as required. Top up as needed.
29) Reconnect the battery negative earth.
30) Perform window reset procedure.
31) Enter code for radio if needed (it wasn't for my RNS-E)

Finally verify that the working temperature of the engine is correct at about 90 degrees celcius.

Result 8)


----------



## qooqiiu (Oct 12, 2007)

Just what the MK2 forum needs!

Well done


----------



## TT-driver (Sep 14, 2010)

Well done! Very smart move to avoid the boot lid from falling into the lock.

Two questions/remarks: in de Audi Service manual, it is written that they use a special pump to let the engine suck in new coolant. Otherwise air might get trapped in the coolant circuit.

Somewhere else I read something about putting back the alternator. Apparently it comes with some sort of special gizmo that should hold it in place. If that was done wrong, the alternator might work itself loose.

Did you turn the heater to max before draining the coolant?

Any comments on these three points?

By the way: I wouldn't reuse any old coolant. It's cheap and better not risk getting any dirt into the system. Fresh coolant also means fresh protection additives.


----------



## poder (Mar 18, 2015)

Thank you for your comments

You don't need any special (vacuum?) pump to do this, just refill coolant fluid very slowly to prevent air getting trapped in the system. There might be a little still, so top up after driving a few miles.

I'm not sure about the gizmo you mention. The alternator is bolted on with two bolts through some bushes. Make sure the bushes have not seized when you tighten the bolts or, if they come loose later, the bolts will effectively not be tight. Tap the bolts on the end of the head with a hammer once they are loosened a round or two, that will do it.

I changed the coolant last year ago when I did the cambelt and coolant pump, so I reused the coolant. I see no problem with this as long as you know it's fresh and the right mixture.
I did not turn the heater to max, as I didn't need all the coolant to leave the system and frankly I'm not convinced that it makes a difference on a modern(ish) system like this anyway :wink:


----------



## hot foot (Oct 7, 2016)

Excellent guide, look forward to using it in the next week or two to do mine, thank you!


----------



## brittan (May 18, 2007)

TT-driver said:


> Very smart move to avoid the boot lid from falling into the lock.


That point has been in the How-To on disconnecting the battery for some time.


----------



## brittan (May 18, 2007)

And poder's excellent How-To has now been added to the KB.


----------



## TT-driver (Sep 14, 2010)

@ brittan: that's where this how to belongs 

I'm well aware that this was mentioned elsewhere too, however, one can't be warned enough in order to prevent that Homer Simpson Doh moment... :lol:

@ poder: indeed it's those bushes I was referring to. Thanks for sharing how to handle those.


----------



## Krs8 (Jun 11, 2016)

Fantastic just what I needed. Just getting prepared to source a garage to fix for me...

Can anyone answer, is the thermostat housed inside this as one part? i.e. two separate parts don't need to be ordered?


----------



## brittan (May 18, 2007)

TT-driver said:


> I'm well aware that this was mentioned elsewhere too, however, one can't be warned enough in order to prevent that Homer Simpson Doh moment... :lol:


I agree: hence highlighting where else that important precaution is noted. 
Nobody wants to crawl over the seats to try out the hatch manual release cable!



Krs8 said:


> Can anyone answer, is the thermostat housed inside this as one part? i.e. two separate parts don't need to be ordered?


Yes, housing and thermostat is one part.


----------



## Steve R (Feb 21, 2017)

Thanks Poder, a good how to, will probably be needing this in the future, but not to soon I hope.


----------



## efunc (Oct 12, 2008)

I needed it yesterday.

thermostat now fitted and enjoying motoring at 90 degrees! [smiley=cheers.gif]


----------



## CurryMan (Nov 20, 2016)

Great guide! My thermo stat is starting to play games and sits on 80 for ageeeeeeeeeeeeeeees before settling to 90 after a further 15mins.

What's the '30) Perform window reset procedure' all about and how do you do that?

Cheers


----------



## poder (Mar 18, 2015)

CurryMan said:


> What's the '30) Perform window reset procedure' all about and how do you do that?


After having disconnected the battery, it may be necessary to perform a window reset. A description can be found here:
viewtopic.php?f=19&t=1504721&p=7960994&hilit=window+reset#p7960994


----------



## CurryMan (Nov 20, 2016)

poder said:


> CurryMan said:
> 
> 
> > What's the '30) Perform window reset procedure' all about and how do you do that?
> ...


Cheers


----------



## Hadaak (Dec 25, 2008)

I have done about 8k km with an 84° oil temp.
I will have to do the thermostat someday


----------



## jameslewisuk (Aug 20, 2018)

Thank you for this guide, successfully replaced my thermostat and no more dropping temps 
The guide was very helpful!


----------



## poder (Mar 18, 2015)

You are very welcome, thanks for the feedback


----------



## Hadaak (Dec 25, 2008)

I installed a camera in the engine compartment to monitor a mysterious tiny oil leak and just found out that the fan started spinning as soon as I started driving the car. The TT had been sitting all day long and the engine was cold. The fan speed varied from time to time. oil temp and coolant temp was still under 50. The fan is turning even at low driving speeds. So my colder temps are probably do to a failing fan or failing coolant temp sensor rather than the thermostat ! Or is the fan spinning triggered by the wind only. It started running under 20kmh !!!


----------



## poder (Mar 18, 2015)

On mine there are two fans. They will spin easily, so a little wind will probably turn them over.
Also, if you have A/C on, they will run while stationary because it requires air flow...


----------



## Hadaak (Dec 25, 2008)

They spin a lot. I'm running at 76-79 C on the highway.
When in town temp goes to 90 C.
I'll go on driving like this till the weather gets warmer and then do the thermostat with the belt and brake servo which started hissing lately.


----------



## Hadaak (Dec 25, 2008)

I took some real time logs of the fuel trim today. They look fine at 70-80c.
I wanted to make sure the open thermostat is not being hard on fuel consumption.
https://log.malonetuning.com/chart/2499 ... HDicKXAAAA


----------



## happychappy (Feb 9, 2015)

Sadly it appears that I will be having to use this excellent guide, so in my usual tradition I have a couple of questions. 

1 - Can't seem to find any info on torque values for any of the parts removed on the knowledge base workshop manual, in actual fact I can't find anything on replacing the thermostat in the WM in the KB! Where can these values be found?

2 - looking at the item on the alternator that needs locking with a 4mm pin I am assuming that this is some form of preset tensioner for the W belt? If not how is the tension set? Usual method of levering with bar? How tight should the W belt be?

3 - I am also having trouble locating a part number, can't seem to find it on the Audi Etka site? I am obviously looking at the wrong section but cannot for the life of me figure out where it should be?

Thanks for any help.


----------



## poder (Mar 18, 2015)

#1 erwin.audi.com has them, but it's not free. You may also be able to find an old, cracked version of the ElsaWin software. Maybe someone else has a better suggestion...

#2 The W-belt tensioner is spring loaded, so you don't set the tension. The tensioner bolts should be torqued to 23 Nm.

#3 I got mine from Audi back in 2016 and my invoice says "06F 121 111 F" but that may have been superseded by a new revision.


----------



## happychappy (Feb 9, 2015)

Thanks very much Poder

Sad thing is I only recently bolted the front end all back together and so would have had unparalleled access!

Hey ho... 

Update

Thanks for a great "how to" Poder, all done now and you were right, I actually found new swear words that I didn't know existed!


----------



## Hadaak (Dec 25, 2008)

I did the timing belt as you all know  but I didn't want to touch the thermostat.
Now that the belt is good I plan to do the thermostat but the 'easy' way by removing the intake. It might not sound easy but I plan to do some valve checking/cleaning after the 163k km I'm at now.


----------



## Wolvez (Jun 22, 2018)

Removing the charcoal canister, idler assembly and alternator is the easiest way. There are 2 tripple square bolts at the front holding the coolant pipe. The hardest part is disconnecting the plastic pipe connected to lower thermostat housing going to the radiator. Also make sure you have a small hose to suck all the silicate sand trap in the engine block.

Use tire marker to mark all Bolts, Clamp and Hose.


----------



## Hadaak (Dec 25, 2008)

Thanks for the hints. I'm going the intake manifold way. Time to see what the 163 km have done there.


----------



## Wolvez (Jun 22, 2018)

Make sure to replace the micro filter on the injector. The Air Compressor Quick Connect fittings fits perfectly to press the PTFE seal to the injector. The replacement injector spacer is made of metal unlike the stock made of plastic. Metal fittings increase idle fuel consumption. It's NUTS to use walnut to remove carbon build up. Carbon buildup can be easily dissolved. https://www.ttforum.co.uk/forum/viewtop ... 7#p9244107


----------



## Hadaak (Dec 25, 2008)

Some good tips and hands-on experience there. I'll let you know when I'm ready to do the job. Next on the list for the moment is the dsg connector seal as per my dsg thread :wink:


----------



## Hadaak (Dec 25, 2008)

Wolvez said:


> Carbon buildup can be easily dissolved. https://www.ttforum.co.uk/forum/viewtop ... 7#p9244107


I don't see the pics in that thread. 
What product did you use? I only read the patent first paragraph  Will go through it tomorrow.
More info please.

edit: found the videos. Good stuff. Promising.


----------



## Wolvez (Jun 22, 2018)

Hadaak said:


> Wolvez said:
> 
> 
> > Carbon buildup can be easily dissolved. https://www.ttforum.co.uk/forum/viewtop ... 7#p9244107
> ...


Carbon buildup is converted to tiny bubbles of co2.

Industrial Grade Carbon Remover - don't buy anything labeled as Automotive Carbon Remover. Ask the people working at your local Home Electric Service provider where they buy AC Transformer Fluid/Oil. You can buy it where industrial grade cleaner (descaler, cement remover, detergent, etc.) and lubricant (Turbine Oil, Food Grade Oil/Grease, Oil Spill Despersqnt, etc.) are sold. I don't know why but most seller sell it only per 55 gallon drum. If this is the case, request for sample and they will give you few liter/gallon for FREE. You need to add Distilled Water on Concentrated Carbon Remover to make it work. The color is yellowish clear like DOT 4 Brake fluid. Smells like Kerosene.

http://www.youtube.com/playlist?list=PL ... yfOEA00MCe


----------



## Hadaak (Dec 25, 2008)

Thanks for the info again.
I will check that out. Do you have a link where you bought the product?
I will ask around to see if I can get easily over here.


----------



## vswizz (May 20, 2019)

Fantastic guide. Mine is sitting at 63C and only going higher on stand still so I'll definitely be using this to replace mine. Cheers


----------



## vswizz (May 20, 2019)

I was looking at buying this one: https://www.ebay.co.uk/itm/FOR-AUDI-A3- ... Sw5WRdnXpZ

The advert says 'thermostat housing'. I'm guessing this will have the thermostat in it? Probably a dumb question, I just noticed that it only says thermostat housing and nowhere does it say thermostat.


----------



## Hadaak (Dec 25, 2008)

I'd get an oem one from audi if I were you. Unless you know who makes it for audi and buy that brand. 
I don't trust ebay for this kind of parts especially seeing the hassle it take to replace it. And if it sticks closed you risk damaging the engine. Audi price is around 70$. Part number (for the bwa engine) is 06F121111F. The part consist of housing plus thermostat.


----------



## Wolvez (Jun 22, 2018)

*OE = Mahle *

The thermostat is inside the housing. Make sure to have a small hose to suck the coolant in the engine block. Sediment from mixing G12 and G13.


----------



## vswizz (May 20, 2019)

Thanks for your responses. I found the Mahle one on Eurocarparts for £29.99 if you put the code in at checkout (they always have code offers on constantly). I've pre-ordered that so I should be doing this job next weekend!

Link: https://www.eurocarparts.com/p/mahle-th ... -209440485


----------



## Hadaak (Dec 25, 2008)

Too expensive there. At that price just get it at the dealer.
See here :

https://www.onlinecarparts.co.uk/mahle- ... 57277.html


----------



## Alex.london (Oct 25, 2019)

I had mine replaced last week as it was stuck open too. Payed £240 fitted, happily paid it based on the guide which made it look a real pain.

Amusingly Audi quoted £700 to replace it...


----------



## bigchunk (Jun 6, 2019)

A big thank you for this diy, I used it today to change the thermostat on my 2009 TTS, it was as listed but I also had to remove my air inlet pipe as it was in the way, only added another 15 mins approx to what is listed in This diy.


----------



## vswizz (May 20, 2019)

Thought I had completed this job this weekend, however I have a coolant leak from the thermostat area 

I noticed this pretty quickly when I started the car up after finishing the job. I removed only the battery and alternator, and could see the area more clearly.

There was a pool of coolant just underneath the thermostat housing. So I got a wrench down there and found that the bottom bolt wasn't fully tight (not sure how because I thought I had snugged it up well the first time, but I may have got preoccupied making sure everything else was connected).

So after tightening the bolt snug and making sure the top bolt was snug also I put everything back together. This time I thought I had fixed it as there didn't appear to be a coolant leak anymore. However after leaving the car on for a while I noticed that there is still a small weep (small compared to before but, still enough to make the coolant bottle go down).

So I'm worrying now that the housing isn't lined up properly. However all the pipes including the fixed metal pipe fit back on snugly. I also gave the housing a good push and it felt like it seated properly when i first put it in, with both bolts going in ok.

So is there a chance the bolts still aren't done up tightly enough? I didn't want to go mental on the bolts as the housing is plastic.


----------



## vswizz (May 20, 2019)

vswizz said:


> Thought I had completed this job this weekend, however I have a coolant leak from the thermostat area
> 
> I noticed this pretty quickly when I started the car up after finishing the job. I removed only the battery and alternator, and could see the area more clearly.
> 
> ...


An update on this; I removed the alternator and checked the tightness of the bolts again - they are definitely tight. I saw underneath the thermostat that there is a small pool of coolant. I put my finger underneath the thermostat housing just to the right of the bottom bolt in the housing and between the contact point of the thermostat housing and the engine there was a slight dampness of coolant. I dried this off with tissue and again the dampness came back. I kept drying this off 4 or 5 times with tissue and each time there was a bit of coolant on the tissue.

So I am not pretty much certain that the part I've fitted is faulty. I lubed up the seal before fitting the part with coolant, and the housing is definitely tight enough, so I don't see what it can be other than a faulty part. Not sure how returning the part will go as its been fitted to the car before noticing there is something wrong with it. More than that I'm annoyed I've wasted so much time (and coolant) trying to get the job done before realising there is an issue with the part.


----------



## poder (Mar 18, 2015)

Do you still have the original part? If so, you should check that they are same size. Did the new housing come with an o-ring or did you reuse the old one? Could it be that you accidentally damaged the o-ring during the install?


----------



## ChipVAG (Mar 7, 2020)

Just used this excellent write up to replace my faulty thermostat.

My TT would struggle to get above 65 to 70° unless I was stationary in traffic for a long time. If it did get up to 90° whilst stationary, it would soon plummet down again when you got some speed up.

It is a mother of a job to do though so be warned, don't think it will take just a couple of hours.

Took me about 5 hours, although a lot of that was taken up getting the bottom pipe back in the thermostat housing, the clip back on the bottom hose on the radiator (the one you take off to drain the coolant) and alternator back on again.

And make sure you have a good quality 5mm XZN bit (otherwise know as triple square) as others have stated.


----------



## SwissJetPilot (Apr 27, 2014)

When I had my radiator replaced, the Audi shop removed the front bumper to get to it. Would that help make this job any easier?


----------



## ihs61 (Nov 17, 2018)

Thank you for the great write up, does any one know if the procedure is different for a 2.0 TDI ?
Regards Ian


----------



## Gone (May 5, 2009)

I've just done this on a BUL A4. Much better access but it still took 6 hours. Fingers crossed there isnt a puddle under it in the morning or there'll be some new swear words created.


----------

