Is the coolant system on a 635CSi under pressure? ....Because seems to be is. Am I looking at a blown head gasket? Or is this normal? - there are no other signs of trouble. the oil's clear, the coolant is clear, the car runs fine. However, the temp needle flickers a bit every now and then. Can you get bubbles in the matrix?

Any suggestions?

Cheers

Art

no pressure but the system can lock in air so there is a bleeder port on the thermostat housing.

I would suspect the sender to gage connection is getting resistance build up.

Here is a picture of the connection, see figure 3.

http://members.roadfly.com/kcroncarter/bmwetm213.jpg

Do I take it from your post that the mechanism that opens the bleeder is governed by a temperature sensor rather than a pressure sensor?

Because if my car isn't overheating how does the bleeder know when to open?

Also any clues on how air gets trapped in the first place?

Cheers

Art