biggles wrote: ↑07 Jun 2019 11:53It seems that more than 500ml overfill is dangerous. Engines have some capacity for overfill. Beyond that oil pressure increase and you could pop an oil seal or cause excessive pressures in the head and get a leak there. Some engines froth the oil if there is too much and air bubbles degrade the oil.
All this was drummed into me by seniors through the years
Did my time as a Cummins Diesel mech, got a newish truck in one day under warranty complaining of low power and poor Jake's braking - that's the heavy noise some of those big trucks make going down hill, its an engine brake and works hydraulically through solenoids from the engine oil.
After checking all was fine with the fuel filters, the fuel pump and injectors were removed and recalibrated, valve timing checked and changed the Jake's brake hyd spools and test drove it convinced the problem solved... Nada
After doing countless test including swopping the turbo and fuel pump from an identical engine, for some reason the oil was drained, maybe thought wrong grade and that was affecting the Jakes brake...
End result I filled it with the correct amount and when we checked the dipstick, it was like 3" below the mark.
Ahhh light bulb went off, sump must have been over filled. So recalibrated dipstick and test drove - bingo plenty power and Jakes brake working fine.
The crank was catching the oil and causing high foaming of oil, this caused the Jakes brake not to work hydraulically as air bubbles compress 5:1 and every time the crank swept through the oil it was costing horse power.
It didnt seem to affect the crank / conrods as suggested and went on to do well over 250,000kms before we saw it again for a piston re-ring job.
Food for thought.