Rocketczar

Hi, I have a really dumb question but I just want to be sure. Where I live it’s about -10 to -15 Celsius now and when I am driving around the city the engine temp gauge reads 80 to 90 degrees. However, when I get on the highway and start driving fast the temp lowers to around 70 degrees. Someone told me that my thermostat might be stuck open. Are they right or is it normal for the thermostat temp to rise and fall?

Thank you in advance.




2001 A4 B5 1.8t Quattro
70,000 km

veedubb

When my car is up to normal operating temperature, it's stuck at 90 and I haven't seen it move from that whether it's city, hwy or cold or hot outside. The regulated temp is usually spot on.

If your temps are fluctuating, then you may have a problem, either with your thermostat, water pump, or you may have air in your system.

The quickest check is to pressure test it for leaks. After that, determine if you may have air in your system by bleeding it. There's a bleed screw on the metal tube on top of the block and there's also a small hole in the upper heater core hose to bleed the system. This small hole is the highest part of the cooling system.

How's your heat in the car? If the thermostat is stuck open, you may not get much heat.

It could also be the coolant temp sensor that sends information to the guage on your dash. It's on the coolant flange at the rear of the block.

**EDIT: This applies for my 2003 B6, not a B5 as you have. It may be similar but I don't know for sure.**

Rocketczar

Thanks for the info. I will try those suggestions. The heat in my care fluctuates with the temp.

But, this problem seems to have started right after the MAF/O2 sensor was replaced a couple of weeks ago so not sure if there is a connection there.

veedubb

I can't see a connection with the work that was done. The biggest give away is that your heat fluctuates with the temp and related to what I had mentioned. Otherwise, I would think it may be connected to the O2 sensor work which may have bumped electrical wiring.

Good luck.