-
Repeat compression test, this time
with about a teaspoon of oil
squirted into each cylinder. (The
oil will temporarily help seal
between piston rings and cylinder
wall, practically eliminating
leakage past rings for a short
time.)
-
If this test yields higher
compression reading than "dry"
compression test, there is
probably leakage between piston
rings and cylinder walls, due
either to wear or to broken piston
rings.
-
Little or no change in compression
reading indicates other leakage,
probably from valves.
Cylinder leak-down test
The most conclusive diagnosis of low
compression symptoms requires a
cylinder leak-down test. Using a
special tester and compressed air,
each cylinder, in turn, is pressurized.
The rate at which the air leaks out of
the cylinder, as well as where the air
leaks out, can accurately pinpoint the
magnitude and location of the leakage.
Before attempting any repair that
requires major engine disassembly,
use a leak-down test to confirm low
compression.
Copyright © 2006 Robert Bentley, Inc. All rights reserved.
Cylinder Head Removal and Installation
http://ebahn.bentleypublishers.com/BMW/3/E46/Repair%20Manuals/1...
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