Date: Sat, 27 Apr 2002 23:12:55 -0500
Reply-To: Chris Stann <ChrisS@INFORMS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Chris Stann <ChrisS@INFORMS.COM>
Subject: Re: 1.9L exhaust system comments
Content-Type: text/plain; charset="iso-8859-1"
> Ok, while on technical subjects - onward to the wizardry of VW water
cooled
> boxer engines. I'm on a roll now . . . heregoes . . . You have an aluminum
> alloy block with water jackets which go up to the head on the outer
> periphery of the head. Inside you have two steel cylinder barrels that
mate
> up with the middle areas of the heads. Eight LONG bolts attach the head to
> the crankcase. This is truly evil. Steel and aluminum expand at different
> rates - so in the heating/cooling thermal pattern of engine operation the
> head gaskets see non-uniform pressures on them - essentially the head
> gaskets are forced to expand and contract. This should not be happening.
> So, my two cents says that head bolt torque is vitally important to engine
> head gasket life.
I've always felt that periodical retorquing of the heads would lessen the
chances of a head-gasket blow-out for the reasons you mentioned above.
Also, changing the head gaskets every few years since old rubber gets less
flexible and isn't able to keep the seal tight during the
expansion/contraction cycle of the engine.
> Anyway. What's this talk of inferior and weak & flexy crankshafts? Due to
> many reasons - flow restrictions and ECU cutoff - the engine won't rev
past
> 5,500 RPM anyway - and I've never heard watercooled VW engines having a
> common failure of throwing a rod or breaking a crankshaft or wearing out
> the main bearings due to "crankshaft flex." I think the lower end is
almost
> bulletproof. I have over 200,000 miles on my 1.9L and usually rev it up
> near 5,000 RPM before each shift - and the previous owner did same and
> cruised the highways of Kansas for hours at 4,500 RPM. Kansas isn't a
small
> state. 4 hours each weekend at 4,500 RPM should rule out any "crank flex"
> problems. OK, if you are some yahoo with Dellorto 42 IDAs and open headers
> trying to turn 7,500 RPM then maybe you have a valid point.
Crank flex is much more common in the air-cooled cases which are made from
softer materials. That's why it's not unusual to have to align-bore them
after 60000 miles. I could see how worn main bearings, quite possibly due
to lackluster maintenance, can contribute to excessive clearances and
eventual ovaling of the main bearing seats.
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