Date:         Wed, 30 Dec 2009 09:49:38 -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:      Fixed -> Expansion tank pressure cap - how tight?
Content-Type: text/plain; charset=ISO-8859-1

On Sat, Dec 26, 2009 at 6:13 PM, Luke Bakken <luke.bakken@gmail.com> wrote:
>> 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.

Well, it turns out that the leak was not from the heater tee but from
nearby where new coolant hose joins up to the stainless pipe. The
screw clamp had loosened enough via heat/cool cycles that coolant was
leaking there. I just had to re-tighten and everything is A-OK.

The reason that I didn't notice this right away is that the leak
didn't start until the engine had warmed up for about 5 minutes - this
time I decided to just run the van in my driveway rather than drive
off to warm up the system. Lesson learned!

Thanks everyone and have a great New Year.
Luke