What does a leak down test tell you?

[pf317]

I was wanting to know what the leak down test lets yuo know.Does it let you know if the rings are not sealed.If only one ring was bad,would it tell you that?Thanks

[newultraclassic]

Originally Posted by pf317

I was wanting to know what the leak down test lets yuo know.Does it let you know if the rings are not sealed.If only one ring was bad,would it tell you that?Thanks

I would think it tells you about the general condition of the cylinders and pistons. That said, a leaky valve could ruin a leakdown test.

You'd probably get more answers in the Twiin Cam area.

[8-Ball]

I thought it gave a clue as to the heads...

[FL84FXWG]

Leakdown test does tell you about the condition of your engine.

Engine is basically an air pump. You have to have good sealing for it to run efficiently.

Leakdown test is pumping compressed air into the spark plug hole.

If a guage is used in conjunction with this you can tell how long the engine will hold the air pressure @ specific pressures.

Then you listen for air escaping.
Air @ carb= intake valve
Air@exhaust = intake valve
Air @ crankcase= pistons or rings

This and a wet & dry compression test will give you a good idea of the condition of the Top end.

IKE

[toybox99615]

you can also check/verify a blown head gasket, hole in top of piston and scored cylinder walls. truly this is a test that experienced mechanics know how to use and one many shop know nothing about. Some of the indications such as air passing through the cylinder to the crankcase result in a need to tear down for actual inspection. For example you can not tell if its a scored cylinder or broken rings without a tear down.

[FL84FXWG]

I made a typo, Sorry.

Air @ exhaust pipe=exhaust valve

IKE