Intermittent Overheating Problems

[Chef_32]

Yesterday my A4 B7 auto quattro overheated in traffic. Coolant overflowed from the header tank, etc. Had to wait for it to cool a little, ran the heating, and kept moving to get it home. It was a hot day yesterday in Houston, high 80s, low 90s probably. I run my car in metric so the temp was at about 38 at some points from road heat etc.

Today there isn't any problem with the cooling, etc.

History is that I was having aircon cutting out in the past, the fans weren't running so I replaced the fan control module, fixed things for a while and then the fans failed so I replaced them, then yesterday again I noticed the fans stopped working. After I got home, I let it cool down for a while and then went back out and this time the fans started working.

Today, its all fine with the fans running, the aircon working, etc. even though its reasonably warm in the 80s.

This has happened before after replacing the fan and control module but not to this extent. The AC will become flaky at traffic lights, etc.

I've ordered another Fan Control Module but I doubt thats the problem. The temp gauge on the dash showed it overheating, and the warning came on, and the Torque app linked to my OBD showed temperature readings as per the gauge so I think the temp sensor is working fine for the gauge. Didn't have any engine light so I'm not sure about any codes coming up, and I don't have access to a Ross tech to do anything fancy.

Is there another temp sensor I should be looking at checking/replacing, any fan switch perhaps?

I'm about to do a timing belt service so will do t-stat and water pump with that but I don't think its the coolant flow thats messing me up.

Any ideas?

[fly300kts]

I would expedite doing your timing belt, water pump and thermostat, that might not be fully opening every time, triggering your issue.

Phil

[Chef_32]

I've ordered the kit from europa, will try to get this done in the next week. Any input on sensors? I want to take advantage of having the front off to replace anything that may be causing the problem

[vvenom800tt]

If your ac isnt working when you are sitting in traffic then your fans arent spinning. If youre overheating in traffic as well but not when driving then your fans arent spinning.

If youre parked and you pop the hood and if your fans arent spinning and your ac is on, then try to push the fan with your finger and see if it will starts spinning, if it does then your fans are bad, if not then it might be the controller.

[Okedokey]

If youre parked and you pop the hood and if your fans arent spinning and your ac is on, then try to push the fan with your finger and see if it will starts spinning, if it does then your fans are bad, if not then it might be the controller.

Caution, the fans can start spinning at anytime - don't chop your fingers off.

[vvenom800tt]

Caution, the fans can start spinning at anytime - don't chop your fingers off.

that comes without saying, but if he has no ac at all when standing still then most likely theyre not moving at all.

[Okedokey]

It doesnt go without saying he could do serious damage, and other, not necessarily member might read this.

[L'Audi]

Fan control module... Been there.

[Chef_32]

The fans are like 1 month old. Will try to replace the fan control module again as well as the waterpump and thermostat....

Won't be chopping fingers off hopefully.

[miA4]

When you say 38 do you mean celcius? if so, that's not even close to operating temp. I would suspect a bad thermostat or waterpump being the issue. Get that changed pronto!

[Okedokey]

He's talking about ambient temperature. 38 is closing in on 100oF.

[miA4]

He's talking about ambient temperature. 38 is closing in on 100oF.

eh... I'm an idiot.