Idle overheating issue😔

[DugiHowser]

Ive read here pretty thoroughly yet still can't seem to get my question answered so I figure Id ask.. In a nut shell the car's temp rises at idle or sitting in traffic unless the AC is on. I know others here posted the same issue but I vitually replaced everything that was mentioned on their posts and the problem still stands.

New:
Waterpump
T-Stat
Green Sensor
Black Sensor
Blue Sensor
Aux Fan Module
Fan Clutch

After replacing all these Im still at a loss. Is there anything Im overlooking? And FYI my fans only come on with the AC on and fan clutch is on constantly even after replacing. No coolant leaks. Could it have anything to do with a fuse or relay? Perhaps Aux waterpump as I have not yet replaced it? Any help will be greatly appreciated!

[Jism]

Simple test: on the bottom left, coolant hose, there's a blue sensor, pull the wire out,

take a paperclip, short pin 1 to 2 for LOW, and 3 to 4 with HIGH.

Fans should come on, if not something else is wrong. Ofcourse when running with AC it drives the left fan cooling the radiator. But it does'nt start the main fan on the front.

[DugiHowser]

Simple test: on the bottom left, coolant hose, there's a blue sensor, pull the wire out,

take a paperclip, short pin 1 to 2 for LOW, and 3 to 4 with HIGH.

Fans should come on, if not something else is wrong. Ofcourse when running with AC it drives the left fan cooling the radiator. But it does'nt start the main fan on the front.

Ill look into that thank you! Regardless the problem would that explain my clutch fun always being on? I just replaced it and wondering why its always engadged..

[getslideways]

Just curious? Does your heater work well? Like blow HOT air at idle? Or only heat with raised RPMs? Also, same question for the overheating. If you are stopped, but raise the RPMs over 2.5k-ish will the overheating temps start to come down?

[DugiHowser]

Just curious? Does your heater work well? Like blow HOT air at idle? Or only heat with raised RPMs? Also, same question for the overheating. If you are stopped, but raise the RPMs over 2.5k-ish will the overheating temps start to come down?

Hey, yea the heater works very good both driving and at idle (I havent tried to confirm though since its the summer). And yes if I raise the RPMs the temp drops back down..

[getslideways]

I just wonder if you still have an air lock/bubble trapped in the system thats hindering flow (these cars can sometimes be really finicky about getting all the air out with the heatercore sitting so high) if you had done anything to open the cooling system prior to this I might look into that. Usually you will get an instance where the heater gets noticeably warmer at higher RPMs, and either cold or luke warm at idle. If thats the case the same scenario could be playing out when trying to cool the car. Low flow would mean less heat is being exchanged at the radiator and explain over heating only at low RPMs. Just a thought.

[Jism]

Airbubbles into the heater system would be removed within 2 miles of driving. That is'nt the problem. His main AUX fan is'nt switching on, causing the car to 'overheat'. It cools down when you turn the AC on, which drives another fan at low RPM.

The clutch fan (or the one on top of the engine) always runs yes. It's independent and always runs whenever the engine is running.

[DugiHowser]

Airbubbles into the heater system would be removed within 2 miles of driving. That is'nt the problem. His main AUX fan is'nt switching on, causing the car to 'overheat'. It cools down when you turn the AC on, which drives another fan at low RPM.

The clutch fan (or the one on top of the engine) always runs yes. It's independent and always runs whenever the engine is running.

But why is it sooo loud!? Lol. I had other B5s before and never sounded like a tracter trailer😔

[getslideways]

Airbubbles into the heater system would be removed within 2 miles of driving.

Other cars, sure, but not always on the B5 setup. Read around on the forum for all the "no heat" threads that pop up every winter. More often then not its from the car not being bled properly after some recent service and the air bubbles didnt just work themselves out through driving (as a result of the heater core being the highest part of the cooling system).

[DugiHowser]

Other cars, sure, but not always on the B5 setup. Read around on the forum for all the "no heat" threads that pop up every winter. More often then not its from the car not being bled properly after some recent service and the air bubbles didnt just work themselves out through driving (as a result of the heater core being the highest part of the cooling system).

So would that expain the clutch fan being at all times as well?

[Jism]

Other cars, sure, but not always on the B5 setup. Read around on the forum for all the "no heat" threads that pop up every winter. More often then not its from the car not being bled properly after some recent service and the air bubbles didnt just work themselves out through driving (as a result of the heater core being the highest part of the cooling system).

I've never had those issues with my RS4 B5. It was a reflush, let it idle for a moment, drive it and done. Knowing how much coolant goes in is also handy. You can specify the exact amount and top it off where it should.

So would that expain the clutch fan being at all times as well?

If your talking about the front fan, on top of the motor ALWAYS on, please read http://www.b5blog.nl/wp-content/uplo...ning_Guide.pdf and know why that fan is there. It provides a permanent cooling unless you remove it completely.

You should test that blue sensor on the bottom left first. 1/2 should trigger LOW, and 3/4 should trigger HIGH. If not then either your fancontroller is gone (I doubt it since it starts the airco fan actually) or another relais is damaged. Please diagnose that the right way.

[DugiHowser]

I've never had those issues with my RS4 B5. It was a reflush, let it idle for a moment, drive it and done. Knowing how much coolant goes in is also handy. You can specify the exact amount and top it off where it should.



If your talking about the front fan, on top of the motor ALWAYS on, please read http://www.b5blog.nl/wp-content/uplo...ning_Guide.pdf and know why that fan is there. It provides a permanent cooling unless you remove it completely.

You should test that blue sensor on the bottom left first. 1/2 should trigger LOW, and 3/4 should trigger HIGH. If not then either your fancontroller is gone (I doubt it since it starts the airco fan actually) or another relais is damaged. Please diagnose that the right way.

Ill look into the relays. I just replaced the blue and green sensor 😕

[getslideways]

I've never had those issues with my RS4 B5.

lucky you

So would that expain the clutch fan being at all times as well?

When you say clutch fan, you mean the one driven by the accessory belt correct? The viscous fan? If so, relays will have no effect on that as it is mechanically driven, not electronically controlled.

However if you mean the electric pusher fan at the front of the car, not the clutch fan, use this http://www.audiworld.com/tech/eng65.shtml to test operation of the sensor as well as the fan control module itself. Its not terribly uncommon for the Fan Module to go bad and put the fan into constant high speed "jet engine" mode when not in the HVAC ECON mode.

[DugiHowser]

lucky you



When you say clutch fan, you mean the one driven by the accessory belt correct? The viscous fan? If so, relays will have no effect on that as it is mechanically driven, not electronically controlled.

However if you mean the electric pusher fan at the front of the car, not the clutch fan, use this http://www.audiworld.com/tech/eng65.shtml to test operation of the sensor as well as the fan control module itself. Its not terribly uncommon for the Fan Module to go bad and put the fan into constant high speed "jet engine" mode when not in the HVAC ECON mode.

I guess I mean the mechanical fan in the front. It sounds like a tracter trailer. And I just fitted a new one which I don't understand why its always engaged? I replaced all fan and coolant sensors and the aux fan module! Thus my confusion in all this..

[Jism]

why its always engaged?

Are you sure that fan controller is NEW and not USED ? Cause i know those things are pricey and people tend to skip a brand new one vs a used one (such as me :D ).

[DugiHowser]

Are you sure that fan controller is NEW and not USED ? Cause i know those things are pricey and people tend to skip a brand new one vs a used one (such as me :D ).

The sensors are new but I did buy the fan controller module used😕..

[Jism]

Your used fancontroller is bricked. I'm 100% sure about it.

It will be a matter of time before the fancontroller completely dies cause it's running all the time. Please replace it with a brand new one or at least a working one (tested before use).

[DugiHowser]

Your used fancontroller is bricked. I'm 100% sure about it.

It will be a matter of time before the fancontroller completely dies cause it's running all the time. Please replace it with a brand new one or at least a working one (tested before use).

Bricked? How so?

[S4NIK8]

If you want to try another fan control module pm me and I'll ship you one to try to rule that out. Just cover shipping both ways for it.

[DugiHowser]

If you want to try another fan control module pm me and I'll ship you one to try to rule that out. Just cover shipping both ways for it.

Thats very nice of you thank you! But, I dont think its the fan module as I just heard the fans running while the car was off. (Then again I could be wrong). Could it be the Aux water pump by chance? I dont think its been replaced in a while..

[getslideways]

Take a video and post it. I think there is some miscommunication between all parties (especially with terminology) and that's causing confusion for those trying to help you diagnose the issue.

[Jism]

Bricked? How so?

My fancontroller did the very same thing. It spin up the front fan all the time, even when it was cold causing a unnecessary load on the vehicle for a fan pulling 15 Amps constant.

This all 'ended' one day with the fan not turning no more, but the complete fancontroller being bricked. The only thing that helped solve the issue was to replace it with a brand new one. Yes i've tried 2 used ones but the first one was Dead on arrival, and the second did not work seamless, so i figured out why go on the cheap and just buy a new one.

Problem solved.