Date:         Tue, 28 Apr 1998 09:15:33 +0000
Reply-To:     Karl Bloss <blosskf@APCI.COM>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
Comments:     Authenticated sender is <blosskf@relay.apci.com>
From:         Karl Bloss <blosskf@APCI.COM>
Organization: Air Products & Chemicals, Inc.
Subject:      compression testing procedure
Comments: To: vanagon@vanagon.com
Content-type: text/plain; charset=US-ASCII

I've searched the archives about compression testing, but haven't
found the answers I was looking for:

Why the open throttle requirement?  Both the Sears compression tester
I bought and Bentley say full open throttle.  What's the deal?
You're not starting the motor anyway.  Does the gas help seal?

How important is it that the engine is fully warmed up?

Here's why:  I tested with a partially warmed-up engine, throttle
untouched (not tied open), and got #1-65 psi #2-175 psi #3-75 psi #4-
120 psi.  Nowhere did it help the pressure to add 30 weight oil to
the cylinder before retesting.  When I retested 1 and 3, the engine
had already cooled down again and I got almost no pressure.

I'm thinking I must have done something wrong, so I didn't bother
spending a lot of time retesting before talking to y'all.

Other particulars:  This was a routine test.  Van has 170k on the
motor, about 20K since PO redid the head gaskets (he got used heads
from another van and allegedly remachined them), doesn't use oil,
doesn't use coolant, power OK (but then I've never driven another
Vanagon).

I'm putting in a new tranny before too long as was wanting to take
the pulse of the motor and thus determine whether to get an AVP and
do the whole drivetrain at once.

Maybe I'll bring the tester to Carlisle and let one of you true
motorhands give me a hand with this.  :-)

-Karl
'87 Vanagon GL Weekender "Beverley"; Trexlertown, PA
http://www.enter.net/~bloss/vw/
VW shop list: http://www.enter.net/~bloss/vw/vwshops