I have an '89 200 quattro that is building pressure in the cooling system almost immediately, before it even heats up. Enough so that it is blowing out the relief valve on the radiator.

My hunch, reaffirmed by my grandfather and an Auto Zone employee, is that there is a blown gasket or cracked head or block. That would cause pressure to push into the coolant system.

But there is no coolant in the oil, no white smoke and no oil in the coolant, that I can see.

Recently we replaced the water pump. It appears that the teeth on the cog are a bit narrower than the rest of the timing system.

Replaced the radiator cap, so it is probably not just the relief valve.

There is no thermostat installed, found that out when trying to see if the thermostat was seized.

It is running pure water until I figure out how to stop the coolant from blowing out of the pressure valve on the radiator cap.

The turbo was modified by a previous owner.


Some of the research I have done has pointed to it possibly being a failing turbo, any merit to this?

Any other ideas?