Ok heres the deal.

I bought a 1999 2.4 A4 a while ago........It seemed funny but every now and again I would need to top up the expansion tank with water. When I stopped it spewed it out of the over flow pipe underneath the tank. It didn’t seem to be too much of an issue, more of a nuisance and I had to always check the levels. The car didn’t get hot, it stayed at 90.

Well last week I had another problem. The car kept boiling and making a noise in the front of the motor, so I decided to take it in and get the water pump, thermostat, belts and tensioners done etc.......All good. The water pump was plastic and had partially seized .

The mechanic has it all back together and has bleed the system, but when he takes it for a drive and comes back and sits for about 30 seconds the water rises in the tank and spews out still. About a litre.
He has tried all different ways of bleeding it, but the result is always the same. Water rises and leaks out. The car doesn’t get hot 90 deg, hes done a head gasket check and thats fine, the waters circulating fine, so hes now at a loss as to what it can be????????
If the car sits and idles for ½ with the cap off nothing happens, the coolant stays at the right level

Anyone had the same problems....Oh and he changed the expansion tank cap as well.

 

Thermostat was replaced and installed correctly?

 

Yeah it was replaced with a new one, and I did ask if he had put it in the right way around.
I got a filthy look and a short yes

I just went down and took a look at the expansion tank.It appears to be covered with hair line cracks.Could this be the problem???????????