I would recommend taking to a shop with a exhaust gas analyzer and sniff the
coolant tank for hydrocarbons which is tell tale sign of a leaking head
gasket.

If air is getting into the cooling system it is more likely the cylinder
head gaskets are leaking and not the rubber water gasket on the heads.

----- Original Message -----
From: "Jonathan Farrugia" <jfarrugi@UMICH.EDU>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, April 01, 2006 5:43 PM
Subject: Re: Air Getting into Cooling system

> John
>
> often people have trouble keeping the system bleed when the head gaskets
> are failing.  try pressurizing the system with air and leave it sit
> overnight then look for coolant the next day.
>
> jonathan
>
> On Sat, 1 Apr 2006, John Connolly, Aircooled.Net wrote:
>
> > Sister In Law's 85 Vanagon is getting air buildup in the radiator after
2-4
> > days of errands. We have bled it, and know we are getting all the air
out.
> >
> > The question I have is where is the air getting IN FROM? Any usual
suspects?
> >
> > We did recently replace the rear heater core.
> >
> > TIA
> >
> > John
> >
> >
> >