David Brown 780 blowby

[woo003]

hi, I have started to notice some oil burning in my David Brown 780. it has come on really suddenly. today I opened the oil filler (which is connected to the bottom of the crankcase) and noticed some combustion gases coming out as well as a "chuffing" sound. however there is absolutely no smoke from the breather pipe or even pressure. why isn't there? surely the breather is connected to the crankcase so any blowby would also come out of there? any help? thanks.

 

[used red MN]

Likely the size of the breather pipe is lessening the strength of the pulsing. Maybe this has always happened in the oil filler and you just never opened it to discover it? Oil use and blow-by do not always go hand in hand. For instance oil rings can break or have excess wear and not control the oil properly yet the the compression rings stay intact and keep the compression contained, that is however unusual. A compression test is one of the ways to assess engine condition. You could start and idle the tractor and loosen the injectors one by one. See if any particular one makes the “oil fill noise” go away. This may not really tell you much if you don’t know if the noise in the fill tube was always there or not. Also see if they all provide about the same drop in engine rpm. If one of them makes a minimal change then you know that cylinder is not contributing as much power as the others so it likely has some problem. This is a check similar to disconnecting a spark plug wire on a gas engine.

 

[nick831]

Is your breather pipe straight out of the lower part of the block with only a single pipe? Or may it have a small cylinder in it which contains steel wool? Could that be all plugged or the breather pipe plugged or blocked?

 

[woo003]

Is your breather pipe straight out of the lower part of the block with only a single pipe? Or may it have a small cylinder in it which contains steel wool? Could that be all plugged or the breather pipe plugged or blocked?

the breather pipe comes out of the valve cover. it has no steel wool in the hose