frepp

hello .
trouble in sweden..
my a8 4,2 2002 runs too hot . it´s getting closer and closer too the red mark on the temp meeter and the electrical extra fan doesn´t start at all. unless i start the ac compressor, but then it doesnt run as fast as it should too cool the engine down to 90 degrees..

how can i examine the fan,, or test it too se what´s wrong, any ideas??

help...

ttuling

If so, check the thermal switch on the lower right (passenger) side of the radiator. It has three wires, to control two fan speeds. Connecting the brown wire to one of the others should turn on the fan.

If it gets also get too hot when driving faster, not in traffic, the thermostat could be bad. If so, the radiator may only be 40 C near the fan switch because so little coolant is flowing. (That's how it was when my thermostat failed last year.) The thermostat on this engine is in a very inconvenient location.

In either case, the third, maximum fan speed should come on when the meter reaches the second long mark after above normal. This is controlled by the instrument cluster, not the switch on the radiator. If this doesn't work, are you sure the fan comes on with the AC compressor?

Kaluluka

Hi!
This is maybe not a Fan problem!
If you recently changed coolant fluid, this kind of behaviour happens if air is trapped in cooling system.
Actually only part where sensor is mounted is getting very hot due to air.
Otherwise you have to hook up your car to a diagnostics computer (Vag-com, Vas 5051) & activate fans manually to see if they run during the test sequence. If they not run then you have a electrical problem.
I hope this could help.
Best regards
Kaluluka

frepp

how can i be sure to get the air out of the system..??
in januari the changed the fluid for me to adjust it for the swedeish climate som that is a possibility..

Kaluluka

Hi!
Ask any (Good) workshop, they can do it without any trouble.
Otherwise if you don't know what are you doing, damage to the car going to be costly!
If you have 2002 A8 it should be covered under warranty. Try this approach.
If you still want to do it your self you have to remove top hose going to thermostat, water pump & try to fill coolant, to engine block, from there.
Kaluluka

frepp

well it´s the 2002 model , bought in 2001 december. so the warranty is out by now.

but i´ll go to a workshop and see what they can do about it.

thanks for the help...

PaulW

Remove the coolant expansion tank cap.

With the car cold, start the car. Put the heater controls on AUTO and put the heat up as high as it will go to HIGH.

Open the heater hose bleeder valves, which are the hoses that go back to the heater core by cracking them open 2 turns.

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/et6.JPG">

<img src="http://www.audipages.com/Tech_Articles/enginemechanical/et3.JPG">

This is the high point of the system. Run the car until coolant starts spewing out of them.....then close them down a little and some more will start coming out of it, but just a little bit. You can close them, but wait until the car warms up and the thermostat opens up.

Then crack them again and vent the system. Make sure you get fluid out of them.

Then top off your expansion tank to about 1/2 between cold and hot and put the cap back on.

Adjust the final level after running the car for a day or so.

Good luck.

mclarenm8d

Of course, it took one failed diagnostic attempt by the dealer. They thought it was air in the system. Ended up being a bad thermostat.

I may be wrong, but I don't think the electric fans will activate on the 5 valve unless the compressor is on.

Either way, if it is a thermostat stuck closed, fans won't really help.

frepp

found the problem..

it was the drivebelt for the valves and camshafts tht was too long, couldn´t tighten it more that caused the waterpump to stand still at low rpm.

new belt and everything is back to normal.