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Has anyone used a percent cylinder leakage tester?

Old Doug

Senior Member
Joined
Oct 16, 2013
Messages
4,486
Location
Mo
I always wanted one and got one a while back i havent had it out of the box till this week. I was testing a gas v6 that they think has a burnt valve and or seat. One cyl i put 100 psi in and it held it one of the others i started turning up the presser i got to 30 psi and it all the sudden dropped from holding 30 to 0 . I let off the presser and started over agin but it wouldnt hold any thing and was leaking air into the intake . I am pulling the head off anyway but why did it start to hold then wouldnt hold anything?
 

skyking1

Senior Member
Joined
Nov 3, 2020
Messages
7,467
Location
washington
It helps to have two people, one who bars the engine and the other guy runs the gauge.
We use that type of tester on aircraft engines, and it is relatively easy because they are equipped with a big bar, the propeller. You can quickly find TDC when the cylinder is under pressure, you feel for it. Do be careful not to get slapped if you are too far off TDC.
 

Old Doug

Senior Member
Joined
Oct 16, 2013
Messages
4,486
Location
Mo
I know i needed to have every cyl at tdc so i got a helper and i marked the balancer to see if it moved. Its a OHC so i couldnt do anything about the rocker arms . I need a tool to remove the timing chain to remove the cams to remove the rocker arms. The tool should be hear today . I hope to have this done later monday to do a retest with the cams removed. Its has 2 overhead cams and 4 valves . I thought if i removed the valve covers i could get it turned were no valves were close to opening but thats hard to do on this engine.
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
I have a Chinese one and the gauges are not worth anything. I just use the adapters in the kit, get the cylinder to TDC which I do not find real hard, and then apply full air pressure to it and see where it comes out. Intake, exhaust, crankase or somewhere else. Valves should not leak at all, crankcase use the feel of a hand so that it is something reasonable, that's the way I test them.
 

skyking1

Senior Member
Joined
Nov 3, 2020
Messages
7,467
Location
washington
don't mess with the rockers and cams.
Pull the plugs, and get your long breaker bar and socket on it. apply some pressure then gently bump the bar back and forth. You feel for TDC that way. When you are in the sweet spot the pressure will go up a bit, then go back down if you go too far. Get it back to the sweet spot and add the rest of the pressure. That is your reading.
We do it engine warm, that may not be possible in your situation.
 
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