Date:         Sat, 26 Dec 2009 18:13:12 -0800
Reply-To:     Luke Bakken <luke.bakken@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Luke Bakken <luke.bakken@GMAIL.COM>
Subject:      Re: Expansion tank pressure cap - how tight?
In-Reply-To:  <6acc6ca40912231926w187f22a0x339c37b43632f60d@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

> enough. When checking the expansion tank, the past 8 or so drives I've
> had to put in about 1 to 2 cups of coolant into the tank before
> driving, which fills the tank to the top. I then put the pressure cap
> on and reattach the overflow hose. When I get back home after tooling
> around, I'll check the overflow tank to see if the level has increased
> - sometimes it does, sometimes it doesn't (hmmm). The expansion tank
> never has any air in it after a drive, but, once the system cools all
> the way back down again, there is an air pocket representing about 1
> or 2 cups of lost coolant.

More info on this problem - I think I've found where the leak is in
the system. Today before driving the van I checked the expansion tank
and sure enough it was missing about 1.5 cups of coolant. I filled it
up, tightened the cap well, and drove off. When I got home the van was
totally warmed up so I decided to have a look underneath and noticed
that it looked like coolant had leaked from one of the tees to the
rear heaters - there was a drop of coolant hanging there. No coolant
anywhere else (the coolant I thought was from a leak last time was
from me making a mess on the refill). The expansion tank was full and
without any air bubbles (i.e. no head gasket problems).

I wiped up the drips and made sure everything looked dry and tried to
reproduce the drip by driving out on the freeway and back, but could
not see more drips! Here's what I think is happening:

* Fill the expansion tank all the way up before taking the van out -
put in 1 to 2 cups of coolant.

* Run the van around and once the system starts to pressurize, the
coolant begins to leak at that tee. Once enough has leaked so the
pressure is back down, the leak stops. The pressure never gets up to
the point where coolant flows into the overflow tank, which is why the
level of coolant in that tank doesn't seem to change.

* Once the system cools, it's missing that 1 to 2 cups of coolant and
I see the air pocket in the expansion tank.

* Repeat from the first step.

Does this make sense? The one part that doesn't make sense to me - if
the system is missing coolant on cool-down why is it not sucking
coolant from the overflow tank? Maybe the hose to that tank has a leak
(it's the original hose) and air is sucking back instead of coolant
(two problems instead of just the one).

Thanks for all your input so far, this list is a great resource.

Happy New Year,
Luke