Date: Sun, 10 Nov 2013 07:38:00 -0800
Reply-To: Don Hanson <dhanson928@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Don Hanson <dhanson928@GMAIL.COM>
Subject: My recent engine tear-down: All is good again
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84 tin-top/westie interior with a 93 Jetta 2.0 liter ABA/1.8 liter
8-vave head (92 rabbit/jetta/etc) inline gas engine with a a 5sp and
Vanagon diesel-parts 50 deg mounting. digifant EFI.
Recently I 'lost' two cylinders in this motor after about 50k
miles. After getting good advice from people here and doing a
preliminary compression test, I pulled the head, leaving the motor in
the van. About 4 hrs of work there...a real mechanic probably coulda
done it in 2..
I found a blown cylinder head gasket, a small breach between
cylinders 3 & 4, across the castings between the pistons. When I
built this motor a couple of years ago I was less than conscientious
with my at-home head milling job, quitting too soon, with some
discolored surface still showing right there where it blew. "Good
enough" I told myself at that time..."The headgasket will compensate
for that little "low" spot " Wrong, I found out. It did go for
about 50k miles before biting me.
Everything else in the motor seems fine. Valves look very good ,
no wear apparent on the cam, the cylinder walls showed nothing bad.
So I got the needed parts to put it back together ($120 worth,
including a special 3-layer $50 head gasket) and this time, I was
meticulous about surfacing my head. I guess I spent about 2 hrs of
careful (and somewhat strenuous, shoving the head back and forth)
lapping on ever-finer emery cloth on a very flat table, finishing up
with 320 grit. This time, "good enough" was put aside and my
completion-standard was "perfect is OK" I also replaced the timing
belt and the injector O-rings as well as found that the green plug to
the injector log, that had both wires bare and shorting
together...perhaps the cause of my intermittent 'smoking sometimes
during stop and go'...
FYI, the head torque specs from Techtonics Tuning are different from
Bently Books..(44ft/lbs+90+90 was what they suggested I use)
So I finished and tested yesterday...after a lot of initial smoke
out the pipe and some alarming bubbles coming into the expansion
tank..("Oh Brother!" I thought..."I get to do this all over again, the
head gasket is leaking again") . Everything settled down in a minute
or two, the air all came out of the cooling system and she runs
like a new motor.
I'll finish up with an oil filter and new-untainted engine oil, a
re-check of the timing belt tension and some new fuel line...
Don Hanson
PS..Why did I choose to surface my own head? Couple of reasons.
First, I don't have a trusted machinist that I am familiar with.
Removing all the valve gear and restoring it after sending out is
pretty involved. It's been my experience that while machines are
time-savers and allow unskilled workers to accomplish difficult tasks,
they aren't always the only or best way to do something. The boys at
T.T. mentioned they see their fair share of botched machine jobs on VW
heads and are particular with where they send their machine work...
So, yes, my arms got tired and my brain got numb pushing and pulling
that lump around, but I know it is smooth and straight.
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