Thermostat stuck open

[Ripstop]

I can only wholeheartedly agree with all the posters saying that the main thermostat does appear to fail slowly over time. My Eddy is 10 years old and is showing all the symptoms described above. When I first bought the car it was ok but after a while I noticed the temp dropping on cruising on motorways, coasting downhill and in cold weather never getting above an indicated 85 unless I was in traffic.

The gauge doesn't appear to be that accurate either as the real water temperature appears to be +- 10 degrees or so as @Dan_FR quoted. The hidden Aircon control (option 19.2) I think shows a more accurate temperature from the cylinder block and I have seen it as low as 65. The fans do kick in correctly once the temperature does get above 89-90 degrees and never gets hotter.
I do think there also maybe a minor adjustment in fuelling as the temperature is never ideally at 90 ish but that's only wishful thinking about my petrol consumption not being more than about 30mpg which is normal for an un-tuned Eddy 

I just hate it not being at 90 all the time.
All in all its booked in to be changed along with the the ubiquitous noisy cam chain and tired tensioner.

[neilw]

Having only had my ED30 4 days I've noticed that the temp gauge tends to sit at about the 70-degree mark maybe just over. I'm guessing from reading on here that that isn't quite right? I'm going to be changing my cambelt and water pump soon so might as well put a new thermo in while the coolants drained?

[AJP]

Having only had my ED30 4 days I've noticed that the temp gauge tends to sit at about the 70-degree mark maybe just over. I'm guessing from reading on here that that isn't quite right? I'm going to be changing my cambelt and water pump soon so might as well put a new thermo in while the coolants drained?

Yeah, that's far from right. Get a new stat in while it's in for the belt.

[pudding]

All you need to know is this:  If the needle does not point bang on 90, it's not right. 

VW engineered the needle sit exactly in the middle (to mitigate customer paranoia) within the large temp range Dan FR quoted.   If it's pointing at 80 or as low as 70, it's seriously overcooling and should be dealt with when you get the chance.

Don't tell anyone this, but I was driving along yesterday staring at the needle, and noticed it wasn't pointing north anymore.  I only replaced the thermostat last summer, so I started to get a bit angry.  Then I realized I was looking at the fuel gauge    Anyone else done that?!   

[Bigjimknickers]

Still waiting for my quote on the thermostat (SE autoworks) not impressed really, shame as I'm local & read good reviews

[JoshJaggard]

Had my thermostat replaced today, stays on 90
And seen an improvement of around 4mpg

[slix]

Mine never gets to 90 anymore.  Only if stopped in traffic.  Once moving again it drops back to 70/80.

Does the main stat going wrong cause this? Or could it be one of the other 2 seeing as I have a dsg.

I'm guessing the main stat causes 90% of these problems listed?

[Bigjimknickers]

Had my thermostat replaced today, stays on 90
And seen an improvement of around 4mpg

I'd love to see that on mine!

[JoshJaggard]

Mine never gets to 90 anymore.  Only if stopped in traffic.  Once moving again it drops back to 70/80.

Does the main stat going wrong cause this? Or could it be one of the other 2 seeing as I have a dsg.

I'm guessing the main stat causes 90% of these problems listed?

Mines a manual, but I just got the main thermostat replaced, I had identical problems do you and has solved it, but not sure if it would be any different for a dsg? The car runs smoother now as well

[AJP]

Slight thread resurrection, and a question:

Can a dodgy thermostat cause any performance loss? Mine has always had good days and bad days, but since I've noticed the needle dropping it's felt a little flat.

I'm not ruling out a bit of a boost leak somewhere - it's been on a rev G DV for 18 months now, a while at Stage 2, so there's a chance that's starting to split.

Could be something completely unrelated of course. Think the old girl needs a bit of TLC!

[slix]

Slight thread resurrection, and a question:

Can a dodgy thermostat cause any performance loss? Mine has always had good days and bad days, but since I've noticed the needle dropping it's felt a little flat.

I'm not ruling out a bit of a boost leak somewhere - it's been on a rev G DV for 18 months now, a while at Stage 2, so there's a chance that's starting to split.

Could be something completely unrelated of course. Think the old girl needs a bit of TLC!

I read somewhere a while ago that you don't get 100% of performance till the car has warmed up fully. I may be wrong though. And yeah check your dv as could be a slight tear.

[slix]

Anyone have the part number for the MAIN thermostat? Cheers.

[Shoduchi]

Anyone have the part number for the MAIN thermostat? Cheers.

06F121111H

O-ring: 06B121119B

[Rogue5]

Had my thermostat replaced today, stays on 90
And seen an improvement of around 4mpg

+ 1 on the above....warms up quicker and gets to 90 now for me, far better than previously (struggled to get it over 70 and sat at 60 most of the time  ) and with better mpg too 

[neilw]

I replaced mine yesterday, as the car wasn't getting to 90. Its a PITA of a job. It was more effort and time doing the thermostat than the cambelt which my mate did for me yesterday morning too. We had all sorts of cooling pipes off, an inter cooler hose, the throttle body just to get access. It took him from 8am until 13:30 to do the belt, water pump and thermostat

The car now feels much better, It feels more powerful and running very smoothly. I also changed my PCV as well so this could of also had an effect.