Bukh 20 leaking oil and strange governing

[GreekYiannis]

Some time ago my Bukh 20 revved out of control or up to maximum. I never really discovered which it was. But the engine responded to the diesel shut-off and stopped, so I was thankful for that. Several people kindly helped me with that. I never solved the problem; just stripped out the diesel injection pump (which seemed ok) felt inside the casing and the springs of the governor seemed ok too. Nothing was broken or cracked so I rebuilt the bits and the engine ran fine. Until now.
Now I have an engine oil leak from the governor spindle and the throttle control seems strange; in that the engine speed is slipping up and down on its own. I removed the throttle and spindle and the nylon conical seal looked unmarked, unworn and generally ok. So I tried removing a shim from under the mechanism to see if I could tighten down the conical nylon seal and stop the leak. But that didn't work, so I tried removing two shims, and that didn't work either. So I began to look further into why this leak was occurring.
I wondered if the crankcase pressure was too high, forcing oil out of the point of least resistance ie the conical nylon seal (which acts as a bearing and seal).
With the dipstick removed and the engine running, I could feel definite strong puffs of air coming out of the dip tube and corresponding with engine speed. I have checked the oil level is correct, so the problem isn't just over-filling. The engine has been running fine, it never produces blue smoke and starts first time. Also, the crank resistance is strong indicating good compression. The oil level has been steady for months - until this leak. So I don't think the piston rings are worn, allowing pressure to fill the crankcase. Also, I removed the oil breather in the rocker cover, blew threw it and heard the flap valve operating and air coming out of the two little holes in the breather. So that's not blocked.
Does anyone have any other ideas why this leak is happening? Also, is there a way to measure crankcase air pressure against a manufacturers' standard?

 

[vyv_cox]

It's quite a time since I had a Bukh but I do recall something similar. The suction for the crankcase breather is provided by a drilling that comes up through the cylinder head into one of the inlet manifolds. It is about 5 mm in diameter and was completely blocked by carbon on mine. Cleaning it out solved the problem for me.

There is some discussion of a similar problem here http://www.marineengine.com/boat-fo...-Bukh-DV20-marine-engine-intermittent-problem although no very satisfactory outcome.

 

[GreekYiannis]

Hello vyv. Thanks a lot. that's helpful because although I did blow through the breather, i did not check that the hole in the head was clear. I think a portable drill and some wire is required tomorrow morning. Good tip. many thanks.

 

[GreekYiannis]

I inspected the crankcase breather hole that comes up through the cylinder head and it was completely CLEAR. But a friend suggested that maybe the crankcase pressure was correct and we just feared the problem was bigger than we thought. Maybe the leak was simply coming from incorrect shimming under the bracket which holds the throttle cable and governor spindle. Plus, if the six dish-washers were wrongly fitted, then too much or too little load would be placed on the nylon seal, possibly making it leak. That seal, after all, is not designed to take high pressures, its just there to support the bracket and keep crankcase splash from leaking. So we tried taking out one dish-washer around the governor spindle and that has helped a lot. Now I just get a teardrop now and again. So I'm off to take out one of the five shims to see if that sends the bracket down enough to seal the nylon seal completely.