PT425 and Robin/Subaru Engine Oil blow-by

MossRoad · Feb 16, 2015

arrow said:
Basically Moss, compression reads just pressure on it's gauge and just begins to tell the story. Sort of reading the book flap to get the gist of the book. A leak down reads percent of leakage. Leak down is more for chasing down where the leak is as air is fed into the gauge adapter and seeing where it exits. If air is coming out the PCV valve for instance, you have a bad piston ring. Coming out of other areas describes if you have a cylinder head or valve leak etc.. Both gauges are inserted into the empty spark plug hole. The only thing that the compression gauge reads is what is being created by the piston. The leak down gauge is fed air or sometimes nitrogen. It is zeroed and then air is blown in which is then dispersed within the engine cylinder to measure first a leakage percentage and then where the leak is as the air attempts to find the least resistive path for exiting.

Thanks!

atwood · Feb 20, 2015

It appears that the mystery blow by has been solved. I talked with the mechanic yesterday and he removed the engine again and ran it on the bench to see where the oil was coming from beyond the blow by. Two of the oil pan bolts were loose and part of the gasket was missing, hence oil in the tub area facilitated by the fly wheel. At this point he took the rest of the engine apart and checked the pistons and rings, both looked good. The missing gasket was found wrapped around the screen for the oil pump. So thought is the gasket pieces around the screen were adding extra pressure to engine there by pushing oil into the carburetor area.

I hope that is the issue and I'm good to go now.

Thanks to all for your input, wisdom and expertise.