2.0TDI 177BHP - Never reaches 90C temperature

[deropke]

Always sit at 70-80C, I had only 2 instances where temp reached 90C for like 1 minute max, just had 15 miles drive and another 15 miles of spirited drive on top and didn't see single time temps reaching 90C, surely thermostat issue.

After doing my own research it seems like it's super common with these engines, and everyone from old threads saying its normal, but I really doubt it, my auto start/stop also doesn't work, maybe because temp never at 90C or maybe I don't know how to use it, as I just bought this car. I also have lower economy than expected, driving nicely 40-43mpg, Spirited 34-37mpg, seems like I'm missing 5mpg or so imo. Any thoughts ?

[Elansear]

I would go for the thermostat, sounds like it’s stuck open. Not sure if it’s an easy job on this engine, it definitely is not on my TT. The temp will also have an effect on your consumption and may well also limit the function of stop start. Once the temp is resolved then look at the other issues if they still persist…

[Crasher]

If the gauge never reads 90 then something is wrong as it should read 90 at a real 77 and still read 90 at 116, it is the way VAG program them to stop people whittling about the readings minutiae.

[deropke]

There are two thermostats I believe how would one know which to replace ?

[Elansear]

This may assist.
Audi Parts catalog - ETKA Online, Audi EUROPA, original Catalog Audi EUROPA (https://audi.7zap.com/en/rdw/)

[Crasher]

PM me your reg

[philipharmes]

Assuming you have a DSG gearbox.

It's almost always the DSG cooler thermostat that fails open, this then short circuits the cooling system & overcools the whole engine.

Follow the coolant pipe from the DSG & you will find the in-line thermostat nearby.

[Rsheen]

My 3.0 tdi A6 gets to 90 c after about 3 miles in winter and sooner in summer. My 2.0 tdi A4 takes 8 - 10 niles in the winter and about 4 miles in summer. If i put on cabin heater in the winter it drops to about 80 c. I considered the thermostat to be faulty so asked for it to be changed under warranty. The dealer said this is normal for 2.0 tdi. I disagreed and asked for it to be changed. The result was no difference at all. To be honest i have my suspicions that they never did change it but can only prove it my going to an indy and paying for another replacement stat. For me a car should be able to reach 90c for tdi and maintain that temperature.
in short I think your thermostat is stuck open.

[Crasher]

Ignore what modern VAG temp gauges read, it is programmed to get to 90 ASAP and stay there to stop people whittling about the minutiae of tiny changes, if it doesn’t something is wrong.

[Johnnych]

I had the exact same problem - precisely as you experienced, bang on. It was the thermostat at the front near the alternator that I had replaced and it solved the problem - ie. not the other thermostat that is difficult to get to at the back of the engine.

[dcheng]

I have the same problem with my car. It was fine when I first purchased it, but a few years ago I noticed it would very rarely reach 90. Even if it does reach 90, it would quickly drop to 70-80. At first I thought it was because I had been driving using ECO (Audi drive select) mode, so I switched back to normal and that did not solve the issue. Recently I have been logging temperatures of G62 and G83 with VCDS, and I noticed both sensors' temperatures would increase together. So I suspected the main thermostat was stuck open. After replacing the main thermostat the problem still persists, and the old thermostat does not seem to be open upon inspection.

Now I think the second thermostat (for EGR cooling) is stuck open causing cold fluid to go into the engine block. Has anyone replaced the second thermostat after replacing the main one?

Thanks.

[Baz72]

Did you get this sorted, I have similar issue on gttdi manual, had w/p and belt changed mine won’t go above 70, got a thermostat but not easy to get at, was there an issue with dpf as no sure if regenerating at low temp
Thanks

[dcheng]

No. Unfortunately I never solved the issue. I was thinking of replacing the other thermostat at the back of engine, but since it's a 10 year old car I figure it is not worth the trouble at this moment. The car drives fine, it's just annoying to see it not reaching operational temperature. Maybe I will do it when belt needs to be changed next time.

[AshBandic0ot]

Having the exact same issue myself. Have replaced both thermostats to no avail. So many places say this is normal but I can’t believe that. The MPG of the car has dropped to around 33-38, no way thats normal and I can only assume its to do with this heating issue. I have used a thermal imager to check the temperature of the coolant and engine block to see if the sensors are bad but this seems to confirm these low temps. I have seen so many people posting this issue but no one has an answer apart from thermostats.
I’ve shelled out for an even more expensive thermostat incase a cheap thermostats the issue. Not holding my breath.

[dcheng]

Seeing many who changed both thermostats to no avail, I am starting to wonder if the cause is a faulty coolant temperature sensor. There is a radiator outlet coolant temperature sender in the coolant circuit. Could it be worth a try?

[dcheng]

In April I changed the coolant temp sender/sensor and replaced the whole system with new coolant. I did not see a noticeable change in temperature. About 2 weeks ago, I cleaned the coolant temp sensor's electrical connector with WD40's electrical contact cleaner, and now the temp gauge on my instrument cluster would show 4 dashes (4th one being 80~90 degrees Celsius) when I arrive work. I then logged the actual temp using VCDS, and the temperature when I arrive work is about 83~86, about 10 degrees Celsius before I cleaned the connector.