Yanmar engine compression

[fpollacchi]

Last year a Yanmar engineer couldn't service my 3gm30 because of "back pressure in the oil sump" I had to replace the engine!!
I've since stripped down the old engine, eg I've taken off the cylinder head and it all looks perfectly fine, except for a wee bit of carbon on the middle cylinder. I had expected to see some cylinder head damage? bit it all looks fine the only other thing I can think off is worn piston rings. is there any other cause ? and is there any simple test I can carry out to find the cause of the "back Pressure"

 

[robmcg]

Has it got a crankcase breather? Was that blocked?

 

[vyv_cox]

Check that the crankcase breather is functioning correctly, not blocked, etc. There is a reed valve in the rocker cover.

 

[fpollacchi]

That was a quick response Thanks Guys, would this cause pressure to build up so much that the dip stick shoots out of the tube and oil spurts into the bilge? If its that simple I'll kick myself and the mechanic!! I'll check that out at the weekend!!

 

[[70521]]

Make sure you send him the bill for the new engine.

 

[robmcg]

That was a quick response Thanks Guys, would this cause pressure to build up so much that the dip stick shoots out of the tube and oil spurts into the bilge? If its that simple I'll kick myself and the mechanic!! I'll check that out at the weekend!!

In extremis, yes it will.