|
I don't remember if the suggestion to do a compression test included doing it first dry and then wet, but it should be done both ways to give some indication of ring wear vs. valve leakage. If you have a blown head gasket, it may be hard to assess the rings/valves with a compression test.
If you can get your hands on one, a cylinder leakage test would be nice. Any aircraft mechanic will have one, as will most shops. If you don't have one of those, you can still pressurize the cylinder with an adapter and an air compressor or air tank. With either the tester or just the air hose, listen for how fast the air leaks, and from where it leaks to locate problems. You might hear it from the exhaust, intake, or by removing the oil cap, or in your case it may bubble out of the cooling system. The valves have to be closed on the cylinder tested and it can be tough to keep the engine from spinning because of the pressure, but it can be done.
I would install a mechanical oil pressure gauge and see what the oil pressure is like on a warmed up engine. This would give some indication of bearing condition.
A cooling system pressure test may give some clue about the coolant in the oil. This test may give different results if done on a cold engine vs. a warm one, so try it both ways.
Checking crankcase pressure or quantity of air discharged can give some idea of ring condition because worn rings allow more blow by. I suppose you could get some idea by blocking the PVC system and running with the oil cap off.
After it has been sitting for a while, like days, pull the oil drain plug, but hold it against the drain hole and see if you have free standing water or coolant that runs out. If you do, drain until the water is gone and you are left with the oil that was floating on top of the water.
If you only have a little bit of water in the crankcase, or if you can bleed the water as mentioned above, I would warm it up, change the oil, and see if the new oil gets contaminated. It could have been a freak thing, or possibly someone put water in it. If you get water out of the crankcase, and you have antifreeze in the cooling system, that would be quite suspicious eh?
If your oil is really nasty, you may just have to change oil once with out warming it up, and again to flush it before you can have clean enough oil to see if the problem returns.
I'm sure others will come up with more suggestions of things to check before tearing it down.
Charley
|
