Engine heating issue - HELP!

silkman · Apr 22, 2016

Hello forum,

I've had an engine heating issue (225 quattro - BAM engine) for some time and I'm trying to sort out with my mechanic with no success so far. Latest work was done today.

The problem: Both fans dont come on as they should. With the engine on, after driving and coming to a stop, the temp passes the 90C mark briefly and returns to 90. This is verified by aircon code 49 (ie no faulty dashpod). Goes up to maybe 105C and returns to 90C.

With the aircon on, both fans work with the engine running so no overheat.

Now if I turn the engine off, the temp will go at 3/4 and touch red zone. This is again verified by aircon code 49 and obviously the problem is that the two fans NEVER come on with the engine off.

So far we've replaced with new Audi parts:
-Main thermostat (this was an older problem; the thermostat was stuck open and the temp wouldn't rise to 90C)
-Green valve
-Fan controller box below the battery with new one.
-Dual thermoswitch on the radiator (this was done today)

We've also checked:
-The circulator aux pump is working when you turn off the engine (you can hear it)
-Both fans work without a problem (both low and high speeds). This is checked by removing the dual thermoswitch plug and shorting the pins with a pair of pliers. Shorting a different pair activates low or high fan speed.

Obviously now with hotter weather the problem intensifies. Any ideas? [smiley=bigcry.gif]

[smiley=book2.gif]

Hoggy · Apr 22, 2016

Hi, Forget using Code 51, it always settles at 90 regardless, Code 49 is coolant & only one to use.
Coolant temp will always rise when hot & stationary, as there is no airflow through rad, until fans cut-in, if engine is running. There is a tremendous amount of under bonnet heat, especially on a turbo engine.
I've had my TT from new, 15 years & never known my fans to run when engine off.
IMO nothing to worry about.
Hoggy.

mattington96 · Apr 23, 2016

Hoggy said:
Hi, Forget using Code 51, it always settles at 90 regardless, Code 49 is coolant & only one to use.
Coolant temp will always rise when hot & stationary, as there is no airflow through rad, until fans cut-in, if engine is running. There is a tremendous amount of under bonnet heat, especially on a turbo engine.
I've had my TT from new, 15 years & never known my fans to run when engine off.
IMO nothing to worry about.
Hoggy.

Precisely. I haven't owned my TT nearly as long, but I own the 225hp and it always runs hotter than any other car I've owned, but it's never been an issue. My fans run when the engine is off if I don't give it enough time to cool down after driving it hard. I got freaked at first, but to my knowledge it's supposed to run a little more hot than what I've been used to.

silkman · Apr 23, 2016

Hoggy, matington.

But that is precisely my problem: the fans never come on when I turn off the engine. :?

I also have to say I always use code 49 to check temp. And today I did the "remove fuse #16 trick" and both fans worked in stage 1 even when I removed the key from the ignition.

I can't think of anything else other than :
1) the new audi dual thermoswitch is faulty or
2) start to check the cabling loom from the fan controller box...

And I also got these yesterday but we cleared them to see if they come back...

Thoughts?

Hoggy · Apr 23, 2016

Hi, As the Rad thermal switch is towards the bottom of the radiator, where it's cooler than where the coolant sensor is, perhaps the temp at that rad position is not reaching high enough to trigger the fans.
I'm sue that's why my fans don't run when engine off.. Ambient weather temps always much cooler in Wales than in Athens.

Code 30 usually just means battery has been disconnected.
Dodgy injector/wiring
Boost leak.

Hoggy.

David C · Apr 23, 2016

silkman said:
Both fans work without a problem (both low and high speeds). This is checked by removing the dual thermoswitch plug and shorting the pins with a pair of pliers. Shorting a different pair activates low or high fan speed.

When you did that test, did the low speed run with the ignition OFF?

Engine heating issue - HELP!

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