Date: Wed, 16 Dec 2009 17:51:03 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: head gaskets
Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=response
I suspect that not all vanagon owners understand that waterboxer 'head
gaskets' are unlike Normal headgaskets.
on normal headgaskets, the head bolts/nuts are clamping down with extreme
force, between too flat surfaces, with a very well made head gasket - either
several layers of material, or in more modern designs multiple layers of
fine metal.
Waterboxer 'head gaskets' are nothing like that.
The head nuts are toqued to only 35 lbs, in order to squease the Rubber, yes
rubber, outer water retention gaskets 'just the right amount'.
The torque of the nuts has nothing to do with how squeased the rubber
gaskets are.- the heads botom out on the barrels, determining the 'squease
distance."
The rubber gaskets need to be squeazed the right amount, too tight, and
they'll pinch and leak before they should, not enough, and they won't seal
that well and be a problem before it should be.
there is a 'step distance' that determines how well the rubber gaskets are
squeazed. It can vary from head to head, particularily with AMC heads.
I have seen AMC heads that don't even sit flat on the barrllels, squeazing
the rubber gasket too much at one end and not enough at the other.
it is possible to machine waterboxer heads to 'fix' the step distance if
it's off, but not many machinists can or will do it.
If the flat surface is pitted, equal amounts of materials can be taken off
both the flat bottom and where the head sits on top of the barrels.
bottom line, it's a dumb design.
And .......unlike normal heads and head gaskets, just resurfacing the bottom
of the head, like a normal head, is not an option.
If you did that without removing material where the barrels sit, you'd not
be squeezing the rubber gaskets enough any more. Both surfaces need to be
done equally, and as I said, not all that many machinists can or will do it.
It's a converted air-cooled design afterall, VW's 'engine conversion ....
hey, let's just put water jackets on the block around the barrels, and keep
the exact same head/barrel/block relationship that we had with the
air-cooled design.
VW has admitted that it's not a good design- they have paid for many to be
re-done, even after out of warrantee.
what I do is check that gap where the rubber gasket goes very, very
carefully. Measure that with head sitting on the barrels with the metal
rings.....the gap between head and block, where the rubber gasket goes.
'The perfect' dimension ., forget what it is right now, 137 thousandths (
inches ) is in my mind right now, but don't quote me on that.
Done carefully ........they can stay on there for a good long time.
Mainly, I wanted to mention that it's not a matter of the head being warped
or pitted and needing simple resurfacing. They ain't that kinda head !
Scott
www.turbovans.com
----- Original Message -----
From: "Dave Mcneely" <mcneely4@COX.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, December 16, 2009 4:34 PM
Subject: head gaskets
> So, I've done about everything I thought I should to make my '91 camper
> as reliable as it could be, including lots of cooling system fixes.
> Just replaced all coolant hoses, since so many think that should be
> done.
>
> First really cold weather of the winter last week. Started up the van,
> only to see a coolant drip underneath. Methinks, well, a loose clamp on
> a hose, not tightened adequately. Take off the lid, search all over for
> a hose leaking. Nada. Continue searching, coolant drip diminishing.
> Stops.
>
> Didn't drive the van for a week. Cold weather returned, and methinks
> the van should be driven a bit. Start it up, and it drips, then drips
> more, then a larger drip, then drips from more than one place. When the
> engine was warmed up, the leak quit.
>
> Head gaskets are leaking. The question: I find it difficult to think
> the gaskets just all of a sudden turned loose (I'd even removed the tins
> to look for evidence of leaks when I did the hoses, and saw none).
> Could it be that the heads and or gaskets were already loose or
> whatever, and the cold weather made them looser and so they leak? If I
> run the engine a little while, the leaks dry up, suggesting to me that
> temperature plays a role -- expansion, contraction ..... . So, could
> the heads be sealed better even with the temperature difference between
> normal fall temps and the quite cold temps we've had lately? I'm just
> trying to understand why this suddenly showed up, and wonder if it being
> coincident with the cold weather is more than a coincidence.
>
> How much should a fix cost? If I need heads milled, am I better off
> having a local guy mill them than buying rebuilt heads?
>
> The engine only has 30K on a rebuild, according to paperwork I got with
> the beast.
>
> Thanks, David
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