Noise after rebuild - leak down test procedules?
 

I rebuilt my 85' 3.2 some time back. Had been running fine, and has a couple track days on it. I recently noticed a sound (like valve's that need adjusting) at around 3200 rpm. Adjusted the valves but the noise is still there. Now there is some smoke upon start up.

I'm thinking I should do a leak down test so I bought a tester. I can't find a published test procedure for leak down testing anywhere.

Can someone point me in the right direction.

Thanks,
Bob

Bob,

Its pretty simple:

1) Park each cylinder very carefully at TDC (firing stroke)

2) With the leakdown tester hose installed in the plug hole, pressurize the cylinder to 100 psi

3) Read the result on the gauge, then listen for the source of any leakage (the is VERY important).

4) Air escaping from the air cleaner means an intake valve problem of some kind
Air escaping from the exhaust pipe means an exhaust valve problem of some kind
Air escaping from the oil tank filler tube means a ring/piston problem of some kind


Don't buy a Harbor Freight one; spend a little more and get a GOOD tool that will give accurate, repeatable results.

Thank you Steve

Hi Steve,

I plan on doing a leak down test this fall, I thought it would be a better idea to have the piston at the bottom of the compression stoke when doing the test. Never done one before but thought if at TDC when you put the air to it, it would push the piston to the bottom of the cylinder, resulting in the unwanted rotation of the engine.

Jim

If it's really at top dead center the piston won't be pushed down. If it's a hair off either way it will.
The factory TDC center mark on the fan housing is not accurate on mine and it's a factory Porsche magnesium fan housing.
You have to remove the fan housing and match up the TDC groove cut in the pulley with the case seam to have it on TDC.

If I remember correctly the fan housing TDC hash mark on mine was a little off towards the right side. Removing the fan housing is easy.

What effect on results for engine cold or warm?

Proportional. Warm engines give a more accurate indication of engine condition due to better ring sealing so thats the preferred way to perform this test.