I have tried all of the tricks with the compression tester and have never been happy. Is there any reason I can't use my leak down tester ? My thought was to get the compression pocket lighned up with the spark plug hole lock the motor in place and preasurize it. and repeat on all pockets. Is there any law in my thinking.

Thanks Dave

have never tried nor had the need to do a leak down on a rota. i dont believe you can anyways. all you need is a compression test and a vacum test to diag a motor.

Nothing at all wrong with using the leakdown gage. They are required to be used once per year on all certified aircraft. Aircraft piston engines leak like a screen door. So, the gage may not help much. It is comparing the .040" orifice between the gages to your engine. So the actual leakage will be some percentage of the inlet air pressure.



Normal compression gages are reporting on actual pressure generated by the engine at cranking speed.



Since leakage involves a time function, the faster the cranking speed the higher the compression reported. So the same engine will show different compression from day to day based on temperature and cranking speed. The rotor need not be locked to use the leakdown gage. Jusr set it at TDC for each rotor face and put the air to it.



Raise the drive wheels off the ground or remove them. Be sure the trans is in neutral. It is no fun to have your baby jump a foot one way or the other when you connect the air.



The engine should be at operating temperature.



Lynn E. Hanover

Thank you that pretty much lines up with my thinking

Dave

i ran across a bulletin for checking the water seals by using a leak down tester. the only thing the mention a couple of times as a caution is to have the engine on tdc, otherwise it'll move...



you also need to check all three faces of each rotor