Date:         Tue, 12 Mar 1996 23:10:26 -0500
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         DHaynes57@aol.com
Subject:      Leakdown testing as requested

A number of people have asked "what is a LEAK DOWN test" and can i do it
myself. First, let me explain the concept.  We already use a compression test
to determine an engines condiditon.  the problem with this test is that there
are too many variables.  It can only be used to check engine condition by
comparing cylinders to each other or a past norm.  Variables such as cam
profile, engine cranking speed etc, will affect the readings.  

A leak down tester uses air from a compressor and measures the rate at which
it leaks through the engine.  This is done with the engine not running and
the beauty of this is that toy can find the source of the leakage by
listening for the escaped air.  Internal leakge is found by air bubbles in
the cooling system.  Tools need are a leakdown tester, and an air compressor.
 The tester is available from Milton at about $60.00.  Compressor should be
at least 2hp and deliver 90psi.

Procedure:  Remove spark plugs.  Set engine to TDC #1. Calibrate test gauge
per the instructions.  Lock engine so it can not turn.  Conect hose to spark
plug hole,  Conect pressurized gauge to hose connection.  Read leakage.  If
looking for coolant leaks and nothing obvious shows up, bypass gauge and
connect shop air direct to cylinder. Open radiator cap before this.  If
coolant sprays out, you have a head problem.  Do same test on rest of
cylinders.  Remember to set TDC of each piston for compression stroke.  This
test is also great for air cooled haed leaks and valve problems.  Note that
all engines will have some leakge past the rings. I always do full pressure
test when I suspect a problem.  Make sure engine is secured with full
pressure test.  it will spin violently.  With gauge connected, you can rock
crankshaft to see if leakage changes.  If so, this is a sign that the ring
lands are wearing,  new engines will also do this until the rings are seated.

I know these instructions are kinda flaky, but I hope this gives some insight
as to this type of test.  If having a mechanic work on your vehicle, he
should be familiar with the leakdown test.  I would be concerned if he
doesn,t.  This is a basic troubleshooting tool that all fleets use.
 Especially on diesels.

Dennis.