Thermostat stuck???

[RJ-B7]

Hello, this is my official first post, so I apologize if I do something wrong.

I own a B7 2006 a4 Quattro manual. 115k miles

I recent did the water pump and timing belt at 112k, it went well. Car is driving great. Recently, I noticed my engine fans turning ON to full blast and the temp gauge move slightly past the middle. I checked and found a coolant leak in the back the engine. I replace rear coolant flange, heater core hose, temp sensor, seals, and seals for the vacuum pump, timing chain cover.
I have not noticed any other leaks. But after 20mins of driving, without running the A/C, my car still gets hot and engine fans turn ON.

Using a OBD11, there are no codes in the car, but the temp creeps past the normal 190-220F range( to about 237F before I turn it off. The fan run for about 2 seconds after shutting off the engine.

I suspected the water pump because I didn’t notice coolant returning to the expansion tank when I revved up the engine. I took out the new pump and it’s totally fine.

I believe my thermostat could be stuck half way, but I’m not sure. It does not show symptoms of being stuck open or stuck closed.

If there is a typo and grammar error , I am dyslexic. Apologies!
Thank you!

[Older_not_Wiser]

Thermostat usually fails stuck open so that when on the freeway temp dives below 180 (Mid) and comes back to 180 in stop and go. It is not unheard of for them to fail stuck in partially closed, but stuck open is more common.

I would make double sure you have bled the system entirely to make sure you do not have an air pocket before tackling the thermostat. Use the bleed hole on the hard pipe as well as the bleed hole on the heater hose, temp cycle a few times checking the bleed screw each time.

[RJ-B7]

I used the bleed hole on the hard pipe to get air out, but I’m not aware of the bleed hole on the heater hose. Are you referring to the heater core hose, which is rubber?

[80sGuy]

The newer thermostats are designed to 'stuck opened' when failed. But I've also heard instances where they can also stuck on closed causing cars to overheat. Try bleeding your lines and see what the result is, if not, at these miles I think it might be time to replace the thermostat. Mine failed at around 60K and I just rode it for a couple more years since it was stuck-opened and finally replaced it last year. Temp gauge has been at dead-center 12 o'clock position ever since.

[Older_not_Wiser]

I used the bleed hole on the hard pipe to get air out, but I’m not aware of the bleed hole on the heater hose. Are you referring to the heater core hose, which is rubber?

Yes, heater core hose. There is a hole in one of them on the core side of the clamp and extra length on the clamp part of the hose, so you can loosen clamp, slide hose off the hard pipe to get hole off of hard pipe and slide clamp to other side of hole and re-tighten. Result makes a bleed hole, primarily for the heater core but helps in bleeding entire system.

[RJ-B7]

I ended up getting the thermostat hosuing. Because I am already exchanging the oil filter housing and it’s right there. I’ll make sure to bleed all the air to leave not chance of over heating.

[RJ-B7]

I didn’t even notice when I exchange the hose. I had air pocket at the heater core with no heat coming out of the vents. It went away while driving.

[RJ-B7]

Update; Replace the thermostat with genuine audi one (ECS tuning). Still no leaks and does not over heat. Ran the A/C and stayed at high RPMs with not over heating. looks like we are good. I accidentally threw away the old Thermostat before i could inspect it. but it was the only thing i replaced.

[Theiceman]

Very common failure . have your car long enough and you will replace all the plastic bits a couple of times

thermostat
PCV
coolant flange
oil filter housing
valve cover
expansion tank

Sent from my SM-G973W using Audizine Forum mobile app

[RJ-B7]

It's been some time, but I did solve this. Replacing the Thermostat fixed my issue, I should have confirmed this by inspecting the old one, but I threw it out before I realized. My best guess is that it was not opening all the way or stuck closed. The replacement wasn't too bad, it took me a full day and im not a professional in anyway. Its been 7k miles and no issues.

[Hockeydad1519]

Hello, this is my official first post, so I apologize if I do something wrong.

I own a B7 2006 a4 Quattro manual. 115k miles

I recent did the water pump and timing belt at 112k, it went well. Car is driving great. Recently, I noticed my engine fans turning ON to full blast and the temp gauge move slightly past the middle. I checked and found a coolant leak in the back the engine. I replace rear coolant flange, heater core hose, temp sensor, seals, and seals for the vacuum pump, timing chain cover.
I have not noticed any other leaks. But after 20mins of driving, without running the A/C, my car still gets hot and engine fans turn ON.

Using a OBD11, there are no codes in the car, but the temp creeps past the normal 190-220F range( to about 237F before I turn it off. The fan run for about 2 seconds after shutting off the engine.

I suspected the water pump because I didn’t notice coolant returning to the expansion tank when I revved up the engine. I took out the new pump and it’s totally fine.

I believe my thermostat could be stuck half way, but I’m not sure. It does not show symptoms of being stuck open or stuck closed.

If there is a typo and grammar error , I am dyslexic. Apologies!
Thank you!

I also have same problem, started just as yours did, found the rear flange leaking and changed that, now it’s fine until I get on highway over really go above 60mph. I ordered a thermostat yesterday? Hoping this is my issue. I also got a temp sensor and a new connector/pigtail as my connector is messed up. But it’s pretty funny how our problems started the exact same way, notice the gauge was a little more than half and started hearing fans a lot.