Those engines were notorious for smoking and being low on oil @ 3,000 mile interval oil change. I was 24 working a a quick lube and this was what I noticed back in 1996-97.
This is one of the best and most accurate tests to perform when diagnosing an ailing engine, diesel or gas. I am a retired diesel mechanic, for diesel engines, the main idea was to listen to the source of escaping air, there were specs for maximum pressure loss. The only thing missing from this video is to make sure the piston is actually at TDC I usually followed that up by holding the crankshaft from turning when air is introduced to the cylinder.
Piston rings are not air tight. Even on a new engine there will be some air leaking past the rings. You’re putting steady constant air into a cylinder so some air will go past the rings and 4 psi is great. When an engine is running the rings don’t have to hold a steady constant amount of pressure. When the air/fuel mixture in the cylinder ignites it creates and instant burst of pressure which cannot get past the rings enough to cause a problem.
JAMES TIBERI, /// ,.///// The Cylinder Leakdown Test will isolate and narrow down if the value train is bad and the intake & exhaust valves are bad, the head gasket is bad by the HISSING air noises? If the Intake is hissing air its a bad valve train the intake valves are bad? if the exhaust pipe is hissing air its bad exhaust valves? if the radiator is hissing and is bubbling its a bad head gasket? If the dipstick is hissing air its bad piston rings? Any others to add to the diagnostic list? Take off the Air Intake and put your ear up to the Throttle body = bad intake valves
