Date: Thu, 14 Jun 2007 11:32:13 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Is this the cause of my engine compression problem?
Content-Type: text/plain; format=flowed
I think your really grasping at straws here. The flat surface of the head
where the rubber gasket meet has absolutely nothing to with where the head
is positioned when tightened down. If ground, milled, altered or whatever,
it will only affect the amount the rubber gasket is compressed. When the
heads are tightened down, it is the top of the cylinders hitting the crush
or metal gaskets pushed into the cylinder recesses that determine where the
head sits. This is also the critical interface relying on both cylinders
being perfectly parallel and level and the recesses in the heads being
properly machined to seal the top of the cylinders to keep the coolant in
the jacket and combustion gasses in the cylinders.
If the heads are properly torqued, it is unlikely the exhaust mis alignment
will cause a head to lift. If it does, you will have coolant system
troubles.
Compression tests alone are often un reliable and as you found out, do
little to tell you where the problem is. You need to do a leak down test to
quantify the leak and then full air pressure to determine where the leak is.
As for the exhaust mis alignment, it is probably the result of an
aftermarket exhaust. This is a common problem. You can;t just bend the pipes
as then the flanges will be at an angle causing the gaskets to leak. best
choice is to drill out the mounting holes.
If you only replaced one liner, it is possible the liner is a slightly
different height than the other. This will keep the head from properly
sealing. This problem again can show up as a cooling system problem due to
combustion gasses getting into the cooling system.
The most important part of any solution is proper diagnoses. This requires
some knowlwdge and the proper tools. A leak down tester and small compressor
is relatively low cost. if you plan doing your own work, the compressor is
almost mandatory anyway. A low cost Milton leak down test gauge is around
$75.
Dennis
>From: David Kao <dtkao0205@YAHOO.COM>
>Reply-To: David Kao <dtkao0205@YAHOO.COM>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Is this the cause of my engine compression problem?
>Date: Wed, 13 Jun 2007 11:25:07 -0700
>
>Over the weekend I put on another 360 miles to my newly rebuilt 1.9 engine.
>I drove my 83 westy to climb some mountains in the western Sierra hills.
>A bit disappointed. Did not get the horses I expected.
>
>Today I checked the compression again. Very strange result. Last week I had
>150, 150, 115, 150. #3 was 90 but when the engine was hot it became 115.
>Today the readings are 60, 160, 150, 160 cold engine.
>
>The #1 reads 60 PSI. The #3 now is healthy 150 PSI. No wonder I felt not
>enough
>horse driving around some National Forest roads over the weekend. The
>strange
>thing is #3 was poor and #1 was excellent. Now they swapped with each
>other.
>
>I think I have an anwer to this. I would like your volks experts out there
>to
>tell me if this makes sense, especially if you have seen it before.
>
>My cylinder heads are in excellent shape (tight vlave guides and no damage
>to
>valves and seats), But these heads are rebuilt heads from a VW dealer 30k
>miles
>back. The gasket mating surfaces were ground and are perfect flat no
>pitting
>whatsoever. But I now see a problem with them.
>
>The distance between the exhaust holes of #1 and #3 as well as #2 and #4
>are
>now slightly shorter than normal due to the fact some metal was ground off
>from the mating surfaces because of rebuilding. This should be fine except
>now the exhaust headers (rear and front) are still at same length.
>
>I remember when I reassembled the front exhause header it was very tight. I
>basically forced it on to the heads. It was bolted on fine but it wass very
>tight.
>
>My guess is that the exhaust header is steel and is fairly large and
>strong.
>It actually pushes my cylinder heads apart from the block. The #3 wasn
>leaking
>last week. Now it shifts to #1. It basically pushed the #1 away from the
>block.
>
>Has anyone seen something like this? Is this a rel possibility? I am
>thinking
>to drop the engine again and take the exhaust header off to enlarge the
>holes
>of the bolts. Or I will send them to a machine shop to bend it slightly so
>that
>they will fit perfectly without working against the heads.
>
>I am determined to fix this engine. This problem probably was introduced to
>the
>engine when it was rebuilt by a VW dealer when it we at 80k. The engine
>never
>regained horses. Now with a new liner and good heads it still doesn't work
>right.
>
>What do you volk experts think? Is it reasonable to suspect that the
>exhaust
>heads are the cause of this problem? Thanks in advance for comments.
>
>David
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