A cylinder leakage test will identify a leaking valve but you'll have to turn the camshaft by hand. Normally the piston is placed at exactly top dead center on the compression stroke but that's only to make the valves closed, (and so the piston won't move down), but the position of the piston is irrelevant. You pump in compressed air through the tool which includes a regulator to limit the air to about 30 psi, then you listen four places for air hissing out.
Air at the tail pipe means a leaking exhaust valve. At the throttle body means a leaking intake valve. At the dipstick tube or oil cap means leaking rings. Bubbles in the radiator indicates a leaking head gasket or cracked head.
You do that test to each cylinder one at a time. You can expect more leakage than normal past the piston rings because the engine is cold and the piston will have likely moved down in the bore. You're only concerned with the valves. If any are bent, you'll know by the sound of the escaping air.
Saturday, March 24th, 2012 AT 6:52 AM