851 Diesel Oil Leak

M-MAN

Well-known Member
Location
Bostic, NC
I have developed an oil leak when running higher rpm's. I sprayed it down with brake cleaner and as long as it's idling it stays dry. Increase the rpm's to about 1200 and it seeps. Gets a lot worse the faster it runs. It appears to be leaking from a couple injector seals but some at the valve cover. It's leaking around the breather too. There is no diesel smell to the oil.

I think the drain holes in the head are probably getting stopped up allowing to much oil to be trapped up top. If so would this affect the injector seals or do I have multiple problems? I really dread pulling the sheet metal and tank again! Any advice would be appreciated.


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Do you have a gasket behind the breather cap? OEM is a cork gasket with a locating notch. Is there a mesh vapor separator inside the cap?
 
I'll have to check the breather gasket. I cleaned the mesh element this spring but can't remember about the gasket.
 
I'm going to try to roll the cover off
first. I know you're supposed to be able
to do it without removing anything else
but that's what they said about changing
the cut off valve too. Hope for the best
and plan for the worst.

The injector seals are what worries me
the most. I don't know if too much oil
trapped on top could cause them to leak?

The seals are ridiculously expensive and
if I have to replace them I'll have the
injectors rebuilt. That's a bunch of
work and money I rather not do unless
it's necessary.
 
(quoted from post at 05:03:23 08/24/21) I'm going to try to roll the cover off
first. I know you're supposed to be able
to do it without removing anything else
but that's what they said about changing
the cut off valve too. Hope for the best
and plan for the worst.

The injector seals are what worries me
the most. I don't know if too much oil
trapped on top could cause them to leak?

The seals are ridiculously expensive and
if I have to replace them I'll have the
injectors rebuilt. That's a bunch of
work and money I rather not do unless
it's necessary.


I have rolled them off a few times. I loosen the tank front and rear and hold the front up with a wedge.
 
(quoted from post at 11:43:03 08/25/21) Thanks! Any thoughts on the injector
seal leak?


I don't think that you have an injector seal leak. What you have circled may be called a seal but it is not an "injector seal" it is just a seal to keep the oil from leaking out from the top of the head, it is needed due to the unusual arrangement of the injectors being under the valve cover. I am confident that once you get the valve cover off you will find fuel leaking from a return line connection. This comes up here regularly.
 
It sounds like blowby. Could be your valve covers not tight enough. If you want to check your injector return lines with the cover off you can use a blowgun and by removing the small return line to the tank at the side of the head, you can mix up a little soapy water to drip on the top of each banjo fitting. I used a syringe from the drug store. Don't worry about a little water getting in there as it will evaporate when you get it up and running. You don't want to stick the blowgun in the fitting just have it close enough to blow some residual air into it. Too much pressure and you might cause a leak instead of find one. I checked my lines this way with those new steel washers and almost all of them leaked. I replaced them with the old copper or aluminum ones as they give when tightened.
 

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