Leak Down Test, How do I do it?

[ntheyer]

I have the 1995 Mercruiser 140 4 cyl where I am having the same issues ast FreeBeeTony (in my opinion). I have done all of the same things he has and still have the same symptoms. I would like to do a leakdown test. I bought an air hold fitting from NAPA and did a test run of replacing valve springs on my old 1974 engine sitting on the floor of my garage and that worked out well. I would like to do the leakdown test on the 1995 engine in the boat but don't know what to do and what to look for as a result? I have a compression gauge as well, so I think I have everything I need? I ordered all new springs yesterday from Mercruiser in hopes that it might be just a weak spring, but would like to confirm that all of the valves are ok. Thanks.

 

[bigbrownbuku]

Re: Leak Down Test, How do I do it?

a leakdown tester is a dual guage set measuring pressure differential. air pressure in vs cylinder pressure. just pressurizing a cylinder will only tell you where if any there are leaks but give you nothing to compare it too.

 

[ntheyer]

Re: Leak Down Test, How do I do it?

Where can I buy one and what sort of readings will I be looking for for this specific engine?

 

[Strtocstr1]

Re: Leak Down Test, How do I do it?

the only thing putting air into the cylinders with a hose and gauge will do, is allow you to "hear" if there are any leaks. A leak down tester has 2 gauges on it, 1 that shows you what PSI, you are puttin ginto the cylinder, and the other the amount of leakage in that cylinder. You might be able to get a rough idea with that air hose fitting... but you have to listen to parts of the engine. Make sure both valves are shut and cylinder is at TDC. then:<br />1. If you hear air thru the intake, its the intake valves.<br />2. If you hear it thru the boats exhaust, its the exhaust valves.<br />3 If you hear it thru the oil fill on the valve covers, its the piston rings.<br /><br />Or you can just go to harbor freight tools, (don't recall the exact website adress) and do a search for any and all sorts of forms of leak down tester, (ie. 'cylinder' 'leak down' etc), it was on back-order for a little while, but I got mine a few weeks ago from there.

 

[scottatwork]

Re: Leak Down Test, How do I do it?

You could just remove all hte plugs, put the guage into every cylinder and crank it over 4 or 5 times (Water attached)....<br /><br />I'm not certain but would think you would see something like 120 to 135 psi (?)

 

[Haut Medoc]

Re: Leak Down Test, How do I do it?

Look in 'search','Leakdown test' page #2 "low cylinder pressure" 2/11/2005. Look at the link posted by Don S., 2/18/2005..........JK