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Date:         Tue, 28 Apr 1998 10:32:28 -0100
Reply-To:     The Bus Depot <ron@NETCARRIER.COM>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
From:         The Bus Depot <ron@NETCARRIER.COM>
Subject:      Re: compression testing procedure
Comments: To: Karl Bloss <blosskf@APCI.COM>, vanagon@vanagon.com
Content-Type: text/plain; charset=ISO-8859-1

> 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.

Karl,

These numbers have me concerned. Even with a cold engine and a closed throttle you should be getting readings in excess of 100 psi in each cylinder. But most importantly, the readings should be relatively even from one cylinder to another (say within about 10%) regardless of what they are. I have seen large variations due to differences between guages, engine temp, etc., but the balance of power from cylinder to cylinder remained consitent from one test to the next - i.e. if a cold engine, miscalibrated meter, etc. causes the guage to read low or high, ALL of the cylinders will read that way, so the "evenness" of the readings from cylinder to cylinder would still be a valid indicator. I have gotten relatively even readings in the over-100 range when testing old engines that were in junkyards or even out of the vehicle, and hadn't even been started in a year, much less warmed up prior to testing.

Now, to present an opposing point of view, one mechanic I trust has opined that in the "real world," low compression should not be a concern in and of itself, as long as the engine is running well and appears to have sufficient power; he says that in actual driving the compression could still be much better than it measures. But personally, I'd like to have seen considerably more even readings than you got. If you are for some reason pulling the engine anyway (not actually neccessary for replacing the trans, as I recall), you may want to tear it down somewhat and check for obvious causes like bad piston rings.

By the way, your clutch kit will be in either today or tomorrow.

-Ron Salmon The Bus Depot http://www.busdepot.com


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