Date:         Mon, 12 May 2003 19:13:12 -0600
Reply-To:     John Rodgers <j_rodgers@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <j_rodgers@CHARTER.NET>
Subject:      Re: Check Compression:  Warm or cold engine?
Comments: To: wilden1@JUNO.COM
Content-Type: text/plain; charset=us-ascii; format=flowed

Stan,
In my aviation mechanic days, we ALWAYS removed plugs from a hot
aluminum cylinder head for a compression check,  but NEVER re-installed
the plugs until the cylinder head was dead cold again. Put a cold plug
in a hot plug hole and  the plug would seize in the plug hole and might
never come out. Case of the chilled shrunken steel ball/ heated expanded
steel ring experiment from high school physics. The mix of the steel
(plug) and the aluminum plug boss would be an even worse case scenario I
would think. I would think the same principle would apply to all the
flat four engines with aluminum heads including the WBX's.

What say you?

John Rodgers
88 GL Driver

Stan Wilder wrote:

>There are up and down agreements on this. (I say up and down because I'm
>getting ready to duck when people start shooting me down on this
>procedure.)
>A warm compression check is most accurate ........... but NEVER REMOVE
>spark plugs from a hot Aluminum Head.
>So before you do a hot compression check, add thread anti seize to the
>plug threads, run the engine till it gets hot and then you can safely
>remove the spark plugs from a hot engine. The engine needs to be at full
>operating temp and it is a PITA working with it at full temp.
>Otherwise do it the country boy method and do it on a cold / moderately
>warm engine by just squirting a good shot of any weight motor oil into
>the cylinder and giving the engine a good spinning with the starter
>before you start your compression check. In either case the anti seize is
>a good idea since it helps seal the threads and you don't have to force
>the threaded end of the compression gauge to get a good seal.
>(There are pros and cons of Anti Seize on spark plug threads, a good
>squirt of Berryman B12 Carb cleaner will remove the anti seize from the
>threads after you've done your testing if you want to get rid of it.)
>
>Stan Wilder
>
>
>On Mon, 12 May 2003 11:09:24 -0700 Malcolm Stebbins
><mwstebbins@YAHOO.COM> writes:
>
>
>>Should I have the engine warm or cold when I check the
>>compression??
>>
>>My van seems to NOT be firing on the right (passenger)
>>bank of cylinders very well.  I've changed spark plugs
>>and wires, the distributor is new as is the cap and
>>rotor and still it stumbles.  It could be carburetion
>>(I have a carb) or it could be a compression problem.
>>Malcolm
>>
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