I have a strange problem:

My '86 Syncro Westy tends to accumulate air in the cooling system. I
regularly have to bleed air from the radiator and I have to bleed air from
the primary coolant tank just about every time I take her out, even for a
short drive.

After about fifteen minutes of running time (either moving or idle), air
accumulates in the primary reservoir and the idiot light comes on at the
temperature gauge (which shows normal temp.). To remedy the situation, I
have to open the engine cover and loosen the cap a little on the tank to let
the air out and siphon coolant back in from the overflow. If I don't do
this, the overflow eventually - you guessed it - overflows and the primary
tank can become completely empty.

I've had my mech check the system for leakeage (couplings, seals, gaskets,
etc.) and he even tried the 'ol cylinder air pressure test to no avail.
Could it be that the cap on the primary tank should be letting excess air
out towards the overflow through the cap and isn't ?

This is really annoying !

Thanks a bunch for any help.

Felix
felixm@total.net

'86 Syncro Westfalia

PS I'm on digest mode, so please cc me personally on your replies.