Working temperature on 2.0 TDIe during winter time

[B5NUT]

As your car is 5 years old I would change the thermostat regardless, they are cheap enough and if you are changing the water pump then you have to drain the coolant anyway. Thermostats don't last forever, and next time the belt will be done is in another 5 years making the stat 10 years old, and on the 2.0TDi engine it will most likely have failed by then.

[Novica]

Thanks for you opinion B5NUT, I was also thinking about it.

I am already changing alternator free pulley due to fear of failure until next cam-belt change. I am changing water pump with all coolant as well. I was thinking to change as well thermostat, but I do not have time to order original one and I do not know which aftermarket to buy.

I was thinking to wait until this fail and then to change. I know that I should change as well coolant then.

If I buy some aftermarket part in my place, I am not sure if this will last until next timing belt change.

[B5NUT]

I would not touch aftermarket version, just get a genuine one. As the 2.0TDi engine was used in all the VW range you should be able to get one from a local vw,seat or skoda garage.

[Novica]

I will think about it, maybe is better preventive repair then corrective after. I will see if I can get one during day tomorrow, if not then will remain his original.

Thanks for replay again

Novak

[crazy4alfa]

it does sound like thermostat is failing. Once the car is up to 90 it should stay there unless you leave the car idle for a long period.

[Novica]

So, I have finished timing belt service. I did not change thermostat. But, today, on country roads, at ambient temp of -2 degrees, going downhill, few kilometers, the temp gauge go below 70 even closer to 50 then to 70. Cabin heating was on. Then I switched off heating and temperature gauge go above 70 but did not reach 90, as soon as I go on flat road or uphill, temperature go to 90 and everything is fine.

I was searching on net and there is lots of similar behavior but I found on one thread that Audi has 2 thermostats and one guy had similar problems (gauge fluctuate only on winter time) and on the end it was some EGR thermostat.

Then, I have looked at E... manual and saw that on coolant hoses diagram is really two thermostats, main under No.15 and EGR - "hose thermostat" under No. 10.



If you follow that diagram, and you suppose that EGR thermostat is stuck open, then when car is going down hill, exhaust gases cannot heat enough coolant and that coolant is finishing into engine and not into radiator resulting in faster cooling of engine. As soon as you go on flat road or uphill, you give some throttle and exhaust gases are warmer and in this manner heat engine faster.

I did not check if I really have this thermostat but I will investigate it these days and if I have it, I will try to block return to engine and see if it will help in keeping temperature at 90 degrees during going downhill.

I have notice that on net there is huge problems about this EGR thermostat on BMW cars. But for Audi I could not find except one thread.

Here it is one more diagram:

http://www.partscats.info/audi/en/?i...ail_id=1756528

As you can see, there is not cat oem number for EGR thermostat only, you have to order whole hose.

Can somebody confirm that this EGR thermostat can cause this gauge fluctuation on downhill (or when engine is not under load) during low ambient temperatures?

[B5NUT]

EGR cooler is pretty small, there is no way it could drop the temperature of the coolant by that much. You should not see temperature drops of that much, once the engine is up to temp then it should hover around the 90deg mark, with around a +/- 10% fluctuation, which you won't see on the dash but can see if your logging with VCDS.

[Novica]

I have ordered yesterday this small thermostat (1K0 121 113 A). As soon as it come I will change it and check if there is any improvement. I am hoping that this small thermostat is causing these drops of needle on low ambient temperatures. I read on net (in skoda forum) that they had similar issues as I have, only difference that they have DSG transmission.

[Novica]

Hello,

Update, today I have received this small thermostat. I have noticed that when I blow air through it, the air passes a lit of bit, not so much.

This evening I have replaced. The old thermostat does also pass small quantoties of air when I blow it through.
I have tried car and no improvments. The outside temperature was aroung 9 degrees C, cabin heating was on 23 degrees C (AC on and fan was working all the time). Car get working temperature in 10 minutes and in 15 km. On flat road and uphill temperature gauge is on 90. But, when I am going downhill, without any load on engine, after few minutes the temperature gauge is moving from 90 to 80, as soon as I put some load it returns again to 90. The car was driven 50 minutes.

Remained only to change this main (big) thermostat.

Will check more these days the behaviour of temperature gauge and if there are big fluctuations (that gauge is going below 70) I will order main thermostat.

Will keep you advised.

Cheers

Novak

[rowdy-999]

Have you considered the temperature sender or gauge may be faulty, or as suggested its a normal trait?
I can't see how even a faulty thermostat, once up to normal temperature could suddenly cause a drop in working temperature? The thermostat is already fully open, so it cant open any more, causing extra cooling.

I think you're worrying over nothing.
Personally I don't care what my needle says as long as i get heat from the heater, or it doesn't overheat.