Connecting air to the tool and setting the pressure so that the first gauge reads 100psi BEFORE connecting to the cylinder. When I do connect to the cylinder, the pressure drops a bit. Do I re-adjust back up to 100psi before taking my % reading?

Thanks,
Rob

Adjust to 100 psi as specified ... connect to cylinder ... do not readjust first gauge.

Thanks.... exactly the answer I was looking for!

I am going to admit my technical ignorance here and say that I am not sure what a leakdown test is supposed to tell one about the condition of an engine. I am curious enough to ask if you would explain and what tools are used. Always willing to learn something new...
Allen

A leakdown test tells you how much air is leaking out of a cylinder. It uses a regulator to set a pressure of ~100psi annd a second gauge to read the pressure after the whole thing is connected to a hose screwed into the spark plug hole. The second gauge is usually calibrated in % so something close to 100 percent would indicate a catastrophic failure. A new engine will have a really low leakdown number. This is usually done a warmed up engine at TDC.

It can be useful to help find where a cylinder is loosing pressure also. If a person hears air hissing when you put your ear at the oil filler it suggests blowby and poorly sealing rings. Hissing from the intake suggests a problem with the intake valve, noise from the exhaust, the exhaust valve. Bad head leaks can sometimes be heard. It helps to pinpoint problems.

Dave

hey allen, if you feel like bringing your 914 over we could check both for leakage over here, i've been tempted to pick up a leak down tester at harbor freight (unless you beat me to it!).

Rob if you have the two gage style you do want to readjust the first gage to read 100 after connecting to the cylinder. You don't have to, but it makes the math easier, (no need for the calculator.) If you have the single gage style you do not reset the gage to read 100 after connecting to the cylinder.

BTW the harbor freight gage is a POS!

that bad huh? how so? i guess i'd be defeating the purpose if i bought it...

Yes, maintaing 100 PSI working pressure makes things easy because the actual values can be used.

The gauges are the bad part of the HF arrangement, you can replace them with something more accurate.

I bought 1, did not work. Exchanged for a second one that did not work. Then I bought one from Ebay that works like a champ (but it is not the HF junk.)

I love HF for some things, but this was not something of theirs that worked.

Zach

never skimp on diagnostic tools!

Can you use the leak down test on a cold engine with a degree of reliability? I would expect more leak down through the rings. I'm looking for ways of evaluating an uninstalled engine.

Hmmm.... Interesting. So I did do it right the first time. Thanks for the clarification!!

I found for myself with the HF tool. I borrowed a tester from Dave Hunt (which is not from HF) and wanted to compare results with another tool. The HF one is the only one I could get right away. I took it back because it did not work right out of the box.



Like I said above, Jake, the first leak down numbers I posted in the engine kit forum are correct then. That makes me feel better!!

Thanks,
Rob