VW diesel thermostat / temp control
Discussion
My work horse car is a '11 Passat 2.0l diesel which has sometimes takes up to 40mins plus to heat up on the m/way and other times will be fully up to temp in 10mins... initially I thought it was a thermostat (I have been told this is a bit of a pain to change and includes removal of the alternator), but for the next week it behaves it self! A couple of weeks later, I get the same problem again for a day or so before it reverts to normal.
The question I have is this just a normal VW diesel engine issue and I should I just change the thermostat or is it some other electrical issue and I will need to get my local VW specialist to find the problem / fix it?
I dont want to leave it like this as I expect it will cause damage to the engineering running cold...
Thanks in advance Alex
The question I have is this just a normal VW diesel engine issue and I should I just change the thermostat or is it some other electrical issue and I will need to get my local VW specialist to find the problem / fix it?
I dont want to leave it like this as I expect it will cause damage to the engineering running cold...
Thanks in advance Alex
Edited by Alexxtreme on Thursday 28th July 22:40
The thermostat is a mechanical valve that keeps the coolant from circulating though the radiator until it reaches approx 85 c ,sounds like its stuck open , driving slowly there won't be much air flow so the engine will warm up , at speed you will have to much cooling , hence sometimes its ok ... other times takes ages to warm up.....
Alexxtreme said:
My work horse car is a '11 Passat 2.0l diesel which has sometimes takes up to 40mins plus to heat up on the m/way and other times will be fully up to temp in 10mins... initially I thought it was a thermostat (I have been told this is a bit of a pain to change and includes removal of the alternator), but for the next week it behaves it self! A couple of weeks later, I get the same problem again for a day or so before it reverts to normal.
The question I have is this just a normal VW diesel engine issue and I should I just change the thermostat or is it some other electrical issue and I will need to get my local VW specialist to find the problem / fix it?
I dont want to leave it like this as I expect it will cause damage to the engineering running cold...
Thanks in advance Alex
Hello. I have a Scirocco 2.0 TDI which I will presume has the same engine as yours.The question I have is this just a normal VW diesel engine issue and I should I just change the thermostat or is it some other electrical issue and I will need to get my local VW specialist to find the problem / fix it?
I dont want to leave it like this as I expect it will cause damage to the engineering running cold...
Thanks in advance Alex
Edited by Alexxtreme on Thursday 28th July 22:40
It sounds like the thermostat. However the Alternator doesn't need to be removed but it is not a nice job at all. Also something to bear in mind, I do a lot of my work myself so I have an account with TPS but in this case my tuner who was fitting upgraded fuel pump to my car kindly said he would do it.
I bought the Thermostat without thinking twice but you need to also separately buy thermostat seal which is not included within the thermostat! Stupid eh :-)
90 degrees on the gauge is anywhere between 75 degrees and 105 degrees C temp.
The minute it starts to move off the bottom, it is 51 degrees C
Mine would usually sit at 90 on the gauge but actual coolant temp was between 77 and 82.. fitting new Thermostat it goes up to 89-92 actual coolant temp and stays there. Economy is much better as well.
Sometimes mine would warm up quickly, other times it would take ages.
As long as you buy thermostat from VW or TPS (genuine parts) you will be fine to change just that.
Hi xjay1337, thanks for your comments.... my car is a 11 reg. Is it the same car with the emission VW recall?
Right - had my local garage change the stat - it came as a complete unit including the housing (he said) for around £25. Changing was a right pain for him which including removing the alternator and removing the aircon pipes (needed a re-charge afterwards). £370 in incl the service
So the drive this am was 16 miles with gentle start then 10 miles on the m/way followed by a couple miles and the temp never went above 75C... it even dropped on a down hill section.
I am sure I did not notice this before the same garage changed the timing belt together with the water pump and tensioner. Any other ideas???
Right - had my local garage change the stat - it came as a complete unit including the housing (he said) for around £25. Changing was a right pain for him which including removing the alternator and removing the aircon pipes (needed a re-charge afterwards). £370 in incl the service
So the drive this am was 16 miles with gentle start then 10 miles on the m/way followed by a couple miles and the temp never went above 75C... it even dropped on a down hill section.
I am sure I did not notice this before the same garage changed the timing belt together with the water pump and tensioner. Any other ideas???
Genuine thermostat is around £45 from TPS (I get a discount as well) so retail is more like £52-53..
Sounds like a non-genuine unit was fitted. If this is the case, this is probably your issue. Only ever use genuine parts for things like MAFs, thermostats, coolant temperature sensors and the like.
Sounds like a non-genuine unit was fitted. If this is the case, this is probably your issue. Only ever use genuine parts for things like MAFs, thermostats, coolant temperature sensors and the like.
Ok - That's good then 
If that part has been changed and it's still not reading correctly try changing the coolant temperature sensor with a genuine unit.
That being said another check is to idle the engine if it gets up to temp but then cools when moving it's the thermostat 99.999% of the time. It is POSSIBLE that the replacement genuine unit was faulty when installed. Not uncommon.
If that part has been changed and it's still not reading correctly try changing the coolant temperature sensor with a genuine unit.
That being said another check is to idle the engine if it gets up to temp but then cools when moving it's the thermostat 99.999% of the time. It is POSSIBLE that the replacement genuine unit was faulty when installed. Not uncommon.
Just saw this thread. Have you got it fixed yet?
If not... I'm guessing it's got a DSG box?
There's an oil cooler on top of the DSG box. Coolant is fed through this cooler. The problem is an inline thermostatic valve which sits right next to the oil cooler.
It's a common-ish problem, but still bloody hard to find any info about it! I spoke with several VW dealers when I saw people talking about it online, and none of the dealers or specialists had ever even heard of this second thermostat!
This is the part you need: http://www.ebay.co.uk/itm/111951626899
I ordered the same part from that seller for my 2012 Passat 2.0 (140) TDI DSG. I believe it's shared among many/all VAG cars with a DSG box, both petrol and diesel.
It's a really easy fix, although you may want to use a garage to properly drain the coolant and make sure there's no air in the system. I didn't bother draining the coolant, but that risks air bubbles. Also the clips are a bit tricky because of limited space.
15 minute job though... Just remove the air filter box and on top of the DSG unit you'll see coolant pipes feeding in and out. One of them will have a valve that looks like the one in that eBay link. Unclip (couple of spring jubilee clip things), stick new one in... Job done!
After that the car would heat up nice and quick and both oil and coolant temperatures stayed perfect. Also MPG went up, which was a bonus
If not... I'm guessing it's got a DSG box?
There's an oil cooler on top of the DSG box. Coolant is fed through this cooler. The problem is an inline thermostatic valve which sits right next to the oil cooler.
It's a common-ish problem, but still bloody hard to find any info about it! I spoke with several VW dealers when I saw people talking about it online, and none of the dealers or specialists had ever even heard of this second thermostat!
This is the part you need: http://www.ebay.co.uk/itm/111951626899
I ordered the same part from that seller for my 2012 Passat 2.0 (140) TDI DSG. I believe it's shared among many/all VAG cars with a DSG box, both petrol and diesel.
It's a really easy fix, although you may want to use a garage to properly drain the coolant and make sure there's no air in the system. I didn't bother draining the coolant, but that risks air bubbles. Also the clips are a bit tricky because of limited space.
15 minute job though... Just remove the air filter box and on top of the DSG unit you'll see coolant pipes feeding in and out. One of them will have a valve that looks like the one in that eBay link. Unclip (couple of spring jubilee clip things), stick new one in... Job done!
After that the car would heat up nice and quick and both oil and coolant temperatures stayed perfect. Also MPG went up, which was a bonus
Brilliant R E S T E C P :-),
I was about to post to say that I have changed the main thermo with still not luck and the problem it seems random. Sometimes it heats up and others it does not. No one I talked to knew of a second thermostat and I had a similar problem on an older BMW 520 where the second thermostat was faulty...
anyway I have brought the stat and will give it a go... the better mpg would be great and it can not do the g/box any good running colder that it should I guess.
Cheers Alex
I was about to post to say that I have changed the main thermo with still not luck and the problem it seems random. Sometimes it heats up and others it does not. No one I talked to knew of a second thermostat and I had a similar problem on an older BMW 520 where the second thermostat was faulty...
anyway I have brought the stat and will give it a go... the better mpg would be great and it can not do the g/box any good running colder that it should I guess.
Cheers Alex
Alexxtreme said:
Brilliant R E S T E C P :-),
I was about to post to say that I have changed the main thermo with still not luck and the problem it seems random. Sometimes it heats up and others it does not. No one I talked to knew of a second thermostat and I had a similar problem on an older BMW 520 where the second thermostat was faulty...
anyway I have brought the stat and will give it a go... the better mpg would be great and it can not do the g/box any good running colder that it should I guess.
Cheers Alex
Exactly the same experience I had, very random problem and difficult to demonstrate to a garage because it always worked when I took it in!I was about to post to say that I have changed the main thermo with still not luck and the problem it seems random. Sometimes it heats up and others it does not. No one I talked to knew of a second thermostat and I had a similar problem on an older BMW 520 where the second thermostat was faulty...
anyway I have brought the stat and will give it a go... the better mpg would be great and it can not do the g/box any good running colder that it should I guess.
Cheers Alex
If I was doing it again I'd maybe ask a garage to do it for me - the clips can be a bit awkward and I probably did risk letting air into the system. But it's a really quick job so don't let them charge you too much.
Good luck!
Alexxtreme said:
are you sure this is the correct ebay part.. is says petrol and no mention of DSG etc?
100% sure. Same one I ordered. I think they're the same for many VAG cars.More info here (you need to register to read the thread): http://www.ukpassats.co.uk/phpbb/viewtopic.php?f=8... including mention of part number 1K0121113A which is what you want.
You could try to check with your local VW dealer, but mine had no clue what I was talking about!
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