Mystery oil leak?

[mherrcat]

Over the past several weeks I have noticed a very strange oil leak. It appears as very fine specks of oil on the fiberglass engine pan and bulkhead area on the right side of (left as your are facing) the engine. Here is a before picture of the area clean and an after picture of the area with the oil specs. This occurs after motoring out of and back into the harbor. I don't usually run the engine more than about 1/2 to 2/3 throttle at most; I don't have a tach so this is just a judgment call. Engine is a Universal M-18.

It does not appear to be coming from the crank shaft seal and I can't locate any other obvious source. I have started to suspect that it may even be coming from the top of the dip stick tube, but the crank case is not over filled. Anyone ever seen this before?

 

[Frank Langer]

Mark, is there any chance that it could be fine rubber dust from your fan belt?(I can't tell from the picture). If it is oil, I can't see it coming from the dipstick, but maybe valve cover gasket, though I'm not sure why it would be flying around in the engine compartment so much...

Frank

 

[Glyn Judson]

Mystery oil leak.

Mark, You may have hit on the problem without realizing it. Could it be blow by from the dipstick tube due to a bad seal there or a dip stick that's not fully seated??? Glyn Judson, E31 hull #55, Marina del Rey, CA

 

[mherrcat]

That is what I thought. It is definitely oil, not belt dust. I looked at the rubber plug end of the dip stick and it looks a lot like a hose barb with three ridges, but there is a groove cut in the first two ridges on either side. I tried putting small O-rings between the first two ridges but that made it impossible to insert the dip stick. I ended up putting a thinner O-ring between the last ridge and the underside of the cap. I guess I'll see next time I motor out of the harbor if it works.

The front of the engine was pretty grimey around the crank shaft pulley so I cleaned it off with de-greaser. I don't really see any noticeable oil leaks there. Seems like it would have to be a pretty substantial and obvious leak to be slinging oil around like that. Or it is blowing out from somewhere, thus the dip stick tube idea.

 

[rwthomas1]

Where is the breather tube located? If the breather tube is spitting oil it could end up on the belt, pulley, etc. and get slung around? Ideally if the breather just vents to air, it should vent to the air cleaner assembly. RT

 

[mherrcat]

The breather was the first place I checked. Nothing happening there as far as I can see. Here's a pic of my re-engineered air filter/breather hose assembly:

 

[erobitaille]

Oil Leak

I had the same issue develop on my E-38 last summer. Glued a hose barb into the air filter cover and ran the breather tube to it. Oil splatter disappeared. I have a cousin who is a diesel mechanic he told me the oil vapor builds up in the breather tube until there is enough oil residue on the inside the tube to start spitting oil. You can clean the tube regularly or just run it back through the engine. I thought the worst last summer when this suddenly appeared, my engine was dying, he did compression checks and a few other things for me and gave the engine clean bill of health.

 

[mherrcat]

I have checked all the breather tube connections and found nothing, but will check them again. I thought if oil were coming through the breather tube it would collect in the bottom of the air filter, and since the air filter is completely exposed it would leak out from there, but it is clean.

 

[mherrcat]

Tried the thin O-ring under the cap of the dipstick on Saturday and did not see any oil specks like before. On Monday I also wrapped a piece of electrical tape around the top of the dipstick and tube; no specs then either.

Seems to be coming from the dipstick tube. Will try for a final confirmation without the O-ring and without the tape on my next trip to see if the specks come back.

 

[rwthomas1]

If the oil specks are coming from the dipstick and this is something new then I would be asking why did it start now? Is the oil level higher than it is normally? I would be looking very closely at the breather hose, etc. If the breather is plugged, clogged, restricted, etc. the crankcase blowby gases will find another way out, like the dipstick tube. This may seem like no big deal but if the blowby gases cannot escape they can push oil out other seals like the rear main crankshaft seal, etc. The other reason that the blowby gases have increased is there is another mechanical problem with the engine. A sudden increase in blowby can be cracked or stuck rings, or some other piston/cylinder bore problem. Your engine may be trying to tell you something. RT

 

[mherrcat]

Ah-ha. I will disconnect the breather hose and check for obstruction next weekend. I know there is some sort of filter element in a small, square fitting where the breather tube exits the top of the engine. I seem to recall that it looked like it would not be a simple task to replace it.

I thought about the oil level as well, but it is at or slightly below the normal full level on the dipstick.