Diesel masterminds....Excess Crank Pressure.

[Alex J T]

Wonder if anyone can help.

At work trying to run a diesel on a test bed, When I reach about 1100Rpm at low load, the Crankcase pressure is building up to a point that the oil rises up the dipstick (the dipstick is pretty much above the turbos - I fit a pressure transducer to gauge any positive crank pressure - had an engine go up in flames recently where the oil dumped on the manifold and turbs)

Anyway - did a quick compression test then - and believed it was the rings causing blow-by (cylinder 2 was knackered), but this current engine has identical, good cylinder pressures?!

The rocker cover breather is ok and clear, cant find any other breathers.

Any ideas what else might cause excess crankcase pressures?

Cheers. Alex.

[stevo]

engine

What type engine are you working on ?

[Alex J T]

Don't think I am allowed to say - its difficult giving the necessary info without giving too much away

Its sorted now though - Main turbos impeller shaft had sheared clean off - didnt notice lack of boost because I couldn't achieve a speed at which the turbo was working before the sump pressurised! Must have been exhaust gasses leaking past the shaft bearing, going down the turb' oil return pipe that was pumping up the sump (never seen the problem before - its usually the rings or a holed piston).

One new mega-expensive turbo later and I have a runner

Cheers. Alex.