jayd2s8

Ok do my 1.8t is acting weird i turn the heater on and the car will start getting hot really fast as soon as i turn it off the temp goes back to normal quickly any advice also my expansion tank has a leak from the bottom when i take the cap off. I get the red coolant light on my dash and when i unscrew the cap fluid goea back to normal levels. Any help is greatly appreciated

John535is

If the expansion tank is cracked, my first thought is it is letting air in when the system is pressurising and you are turning the heater on, this air is then creating an air pocket which the water pump cannot deal with. As an experiment, try bleeding off from the bleed screw. Then run the engine, turn the heater on, when the problem comes back, bleed off again. If you do this 2 or 3 times and you are continually getting air out the bleeder, then its getting in somewhere and the leaking expansion tank is likely.

I assume the thermostat is working when the engine is running without the heater on and you don't have any other tell tale leaks.

jayd2s8

Where is the bleeder screw located?

John535is

Coolant pipe runs along the top of the engine above the inlet manifold. Black metal pipe about 3/4 inch diameter. In about the centre of the pipe, there is a plastic bleed screw. Now if you have not used this in recent times, clean it first to see if it is the metal screw or the black plastic one. They tend to break after 10 years, they are cheap enough to replace ($5-$6) but if you break it off and the coolant comes out without a replacement it can leave you stranded. Who knows why they changed from metal to plastic, early B6 had metal. I can only assume they were having issues with the metal threads and the coolant reacting. Its just a M10 thread, so absolute worse case you can replace with an M10 * 16mm bolt with a sealing washer to get you going.

Part number for the plastic one is WHT000316 (if you look it up on the net it shows you a picture of the bleed screw). They are available from all the usual on-line retailers.

Some debate about replacing them, should you use the plastic or the metal. I figured I won't own the car for another 10 years so the original plastic will suffice.