2.0TDI 177BHP - Never reaches 90C temperature

[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.