Now that I have my carb troubles solved, I am turning my attention to what appears to be a signicicant oil leak that has developed. I have ruled out the oil filter, drain plug, valve covers and gauge feed line as sources. I suspect it may be the rear main seal. Is there anything else I should check or replace before tackling the rear main seal? Is it possible to get a large amount of oil leaking from the rear intake seal? I do have some oil puddling around the intake bolts. The oil seems to be coming down from above the rear of the oil pan and drips onto the exhaust creating a nice smoke screen. The engine is a base 327 that was professionlly rebuilt about 12 years and 10,000 miles ago.
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Re: Oil Leaks- '66 Coupe
Yes, it IS possible for the oil to leak at rear intake seal! Original style gasket was in multiple pieces (front/rear vs. sides) and it requires correct sealing proceedures at the corners for the system to work as designed. Suggest you hose down the rear apron of the engine block (quarter car wash) and mop 'er clean dry with a towel. Then, keep your eye on the valleys of the rear apron that will 'puddle' oil if she's leaking from there.... -
Re: Oil Leaks- '66 Coupe
Once you wipe down the area, either dust some talcum powder or spray some Dr. Scholl's Foot Powder (really ) on that clean area, and the source of the oil will be apparent very quickly after you fire it up.Comment
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Oh!
And don't forget to put your Sherlock Holmes magnifying glass on the base of the distributor too! If there's no gasket there, leaking oil will ALSO migrate to the rear apron....Comment
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Check this out, Sherlock.
Engine oil leaks, especially minor ones, can be a bear to run down. The oil will invariably migrate to the lowest spot, which is the back of the pan.
The rear mail seal is often condemned without a fair trail. Basically, unless the back of the flywheel is wet, it ain't the rear main! You can verify this by removing the inspection cover at the bottom front of the bell housing to inspect the front side of the flywheel.
I've been chasing a leak on my Cosworth Vega that I suspected was the pan gasket. Everyone told me it was the rear main (an old fashioned "rope seal"), but I refused to believe it because the front side of the flywheel is bone dry.
I suspected the high pressure oil gallery that feeds the head because a tiny trace of oil was apparent on the RF corner of the case, but that wasn't it either. Turns out it was either the inlet cam seal or the plug on the face of the cam. (the cam journal oil gallerys are gun drilled passages in the middle of the camshafts.) I didn't take any chances and just replaced both the seal and plug. Note that these two sources are diagonally opposite the rear main, as far away as can be!
Bottom line is that oil slowly ran down behind the belt cover on the front of the engine, then migrated along the pan rail to the very back of the pan. From there it migrated behind the curved lip of the inspection cover that fits snugly between the back of the pan flange and case, and when enough accumulated it would drip out the vent between the inspection cover and the bellhousing - exactly where a leaking rear main would drip. The minor leaks are the toughest, but don't condemn the rear main until you have checked all other sources.
Like Jack says, the distributor is a good place to start along with the valve covers. Also, carefully check the pan rails. The oil might be coming from somewhere up front and migrating down the pan rail to the back of the pan - just like what happened on my CV.
DukeComment
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P.S.
If you have oil oozing out of the inlet manifold bolts, then the inlet manifold is suspect, especially the rear gasket between the manifold and valley. You can pull the bolts, clean and seal them, but if it's the rear manifold to case gasket, you'll have to pull the manifold, but that's a lot easier than replacing the rear main.
Those old rope seals usually don't create a big leak in a short period of time. As mileage builds up they'll begin to seep very slowly, but the oil doesn't get on the exhaust pipes.
DukeComment
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Good additional point(s)
Especially on the valve covers. Much depends on whether restorer PROPERLY straightend/flattened inside surfaces before installation AND whether he applied gasket sealer PROPERLY. I've seen valve covers that looked good, but cylinder head oil was migrating up/on-top of the gaskets and out the bolt holes. Of course, once it's out and onto the top rails of the valve cover, air pushes it back and onto the rear apron.
Mr. Hinkely's point about sprinkling some talc powder to get an 'audit' trail is excellent advice!Comment
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