How?
A compression test will not reveal a tiny leak which is plenty to pump up
the cooling system with air.
I had this exact same problem with my 85 sunroof GL.
Got progressively worse because air in the system continues to overheat
stuff. Eventually it got so bad I had to admit it was the heads.

The cooling system runs pressurized so any leaks will not allow air to enter
but instead create a leak of antifreeze on the ground.

Betcha a nickel its the heads.

Doug

Doug

----- Original Message -----
From: "John Connolly, Aircooled.Net" <john@AIRCOOLED.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, April 01, 2006 6:06 PM
Subject: Re: Air Getting into Cooling system

> head gaskets are fine, already checked that.
>
> John