Oil leak near starter? What's behind starter?

[Mkman13]

Hi folks--I've got a 2011 Mercuriser 4.3 MPI that is leaking oil somewhere in the back. I'm 99% sure it's motor oil, as opposed to drive lube or something else, but I could be wrong. The only place I can find wet oil appears to be behind the starter. I know that doesn't make any sense, and I've looked everywhere I can above the wet spot and can't find where it could be coming from. I'm also having a hard time figuring out what's behind the starter. (Warning, non-technical language coming)--you can see in the picture a flimsy little plastic piece (which is cracked.) When I removed that little plastic cover, the piece behind it had a curved groove, almost like an emergency/overflow vent and that was where the oil appeared to be coming from. The leak only occurs at higher RPMs and higher speeds, not when idling or revved in neutral on the lift.

Thanks a ton for any ideas.

 

[Paintman1960]

I have worked on many GM V8 engine, never a 4.3
Rear main maybe?
Im interested in knowing too..

 

[TwoCamSam]

My guess is it’s probably coming from higher up, like the valve cover. More likely than a rear main.

If you have any suspicion that it is the rear main though, you can remove that plastic cover at the starter. That’s your flywheel inspection cover. Your flywheel would have signs oil on it if it were a rear main.

Valve cover is much more likely though I think.

 

[Paintman1960]

Agreed, but he said he looked up above it ..

 

[Rick Stephens]

I'm gonna be on the same page: rear main, flung by the flywheel, or valve cover gasket.

Yeah, there's a plug for the oil gallery and for the camshaft on the back end of the block, but that would be rare. More likely valve cover leaking down onto flywheel cover, following it down to starter.

 

[Paintman1960]

Possibly china wall seal, I'm still thinking valve cover ,
But I been wrong before ..

 

[Mkman13]

Hi folks--Thanks so much for your feedback! Based on this info and my observations I'm leaning towards rear main seal leak. Does anyone have advice on confirming that diagnosis? There appears to be some oil behind the flywheel inspection cover, which may be confirmation, and I really can't find anything from any of the valve covers, headers, etc.

Thanks again, folks!

 

[TwoCamSam]

I'm not as familiar with the MPI, and I'm still learning on my 4.3L carb, but I might be inclined to replace the PCV valve and check the hose as well. It's cheap and easy. Mine aren't serviceable on the carb motor, but I believe the MPI motor they are.

You mentioned it really shows a leak at higher RPM. You could be building too much crankcase pressure if the valve/hose are clogged. If it can't vent through the PCV, the next weakest link is a seal. The pressure has to go somewhere.

Back stepping a bit on one of my last posts, even if the leak is up higher, but dripping down the starter/inspection cover, more than likely it's getting on the flywheel, so that is no sure fire way to say it's a rear main.

If it were mine, with valve cover gaskets much easier to replace (and nothing really else in the area that could leak), I would be inclined to do them anyway before I pull a motor to do a rear main. I would replace/check the PCV valve and hose before anything and see if it slows or even stops the leak.

How much oil is it leaking? How long has it been leaking? I looked at your photos again. Is all of that brown in the bilge oil?

 

[tank1949]

Hi folks--Thanks so much for your feedback! Based on this info and my observations I'm leaning towards rear main seal leak. Does anyone have advice on confirming that diagnosis? There appears to be some oil behind the flywheel inspection cover, which may be confirmation, and I really can't find anything from any of the valve covers, headers, etc.

Thanks again, folks!

10 years old? How much a leak vs cost and personal satisfaction in repairing it. Pray it is valve cover gasket because they are MUCH easier to fix. Years ago there was a product that would soak up oil in bilge. Now, I don't know... 409 works real well. Good luck.