@stevebuchanan posted:Roland and Doug,
The leak down test showed an intake valve and an exhaust valve leaking on that head. Now that the head is on the bench, the gasoline test shows the intake valve sealing and the exhaust valve leaking. It appears that a leak down test is a more stringent test than the gasoline test. Have you come across this before where a valve passes the gasoline test and then leaks once installed?
gasoline is usually a good test substance because of very little surface tension… and it easily administered.. when the engine is apart!
… leak down test is usually implemented if you get low results in a compression check.. this gives you the ability to detect where the leak is..
like head gasket into water jacket or neighboring cylinders , valves, piston rings or bores…
there is a % of acceptable leak down, which makes sense obviously for certain discoveries…
I personally stipulate 5% as still pretty good, 10% says to me start saving money for a rebuild!
10% can still run pretty good as the high pressure is only lasting for a split second but will “inject “ high temp and deposits into areas where they should not be and will accelerate the deterioration..
I wouldn’t drive myself crazy about that subject.. it’s a car engine and not a submarine…. Some minor leaks are okay.. especially with new parts.. rings not sealed…. And so on..
all of the above is just my opinion… others may think differently!