Oil leak

[rally 1]

Just finished rebuilding a customer engine, inserts, HC cylinder head, pistons, rings, etc.

First two hundred miles, no issues.
Now, when driving for twenty-thirty minutes, when stopping, a major oil leak from the rear of the engine. Dripping out the bottom of the clutch housing.
What I've done so far,
I dropped the pan, thinking that the pan gasket had blown out. Changed the gasket, checked that the drain tube was in place (it is), inside of the engine is spotless.
I installed the pan, new gasket, let sealer setup for a day before adding oil.
Observing the engine running while looking at the flywheel, rear main, no oil coming from the rear main. In fact, the flywheel is dry.
Still has the oil leak after driving.

No water in the oil.

Someone mentioned that perhaps the oil was not draining back fast enough, due to a clogged drain tube. I plan to check the drain tube tomorrow morning prior to pulling the engine. Has anybody seen that happen.
I would think that even if the external drain tube was blocked, the oil ports feeding the rear cam would be the only source of oil to the back of the engine.

Any thoughts as to cause?

Ken

[Art Newland]

If the oil filler tube gets restricted, the crankcase pressure will blow oil out the back.

[Mitch//pa]

Check to see if it's coming from the rear camshaft gasket

[700rpm]

What Mitch said. That gasket needs a light sealant around it.

[Joef21]

Did you put a gasket between belhousingand engine. If not the will leak there. Also check for a cracked belhousing.

[Benson]

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I saw a rebuilt inserted engine which leaked oil after turning it off.

Final fix was to remove the "freeze plug" in the rear main bearing cap. Inside was a small "glob" of dried silicone rubber that was stuck against the top end of the bearing cap drain tube, partially blocking the draining of the oil to the oil pan.

It was weird that this leak would stop while engine was running and leak when engine turned off.

Never did figure out why it did not leak while running.

But after removing the "silicone glob" it stopped leaking...

[James Rogers]

Benson has a good idea but I would also look at the crank to see if the slinger has been removed and a "Modern seal" has been used. Never seen one that didn't leak soner or later.

[BILL WILLIAMSON]

If you push the oil cap down HARD & bend the tabs, it will build up pressure & leak out of the rear of the engine like a SIEVE!
Bill Been-there

[SeaSlugs]

Originally Posted by Benson

I saw a rebuilt inserted engine which leaked oil after turning it off.

Final fix was to remove the "freeze plug" in the rear main bearing cap. Inside was a small "glob" of dried silicone rubber that was stuck against the top end of the bearing cap drain tube, partially blocking the draining of the oil to the oil pan.

It was weird that this leak would stop while engine was running and leak when engine turned off.

Never did figure out why it did not leak while running.

But after removing the "silicone glob" it stopped leaking...

hmm could it have been acting like a one way check valve? (silicone gob)

[rally 1]

Thanks for the feedback.
Because there isn't any oil on the flywheel, leads me to think that the gasket between the flywheel housing and the engine has given up the ghost.
Pulling the engine this morning, will pass on what I find.

Ken

[Benson]

Originally Posted by SeaSlugs

hmm could it have been acting like a one way check valve? (silicone gob)

Yes it is possible as the "glob" was small enough to move inside the horizontal drain hole inside the bearing cap.

But was stopped when it got to the smaller pipe at the 90 degree turn where the drain pipe screws into the rear main bearing cap.

Maybe the "glob" was moving forward and backward inside the horizontal pipe, like you say, so that it sometimes blocked the drain?

Looking back on it ... the clue was there when the oil pan was removed.

This was a short block and the customer had used about twice as much silicone sealer on the pan as was needed.

There was sealer that had oozed out from the joint where the gasket meets the pan and block.

Maybe when he was applying the sealer the "glob" of sealer must have found its way into the rear main cap past the oil slinger on the crank ... who knows?

[SeaSlugs]

Originally Posted by Benson

Yes it is possible as the "glob" was small enough to move inside the horizontal drain hole inside the bearing cap.

But was stopped when it got to the smaller pipe at the 90 degree turn where the drain pipe screws into the rear main bearing cap.

Maybe the "glob" was moving forward and backward inside the horizontal pipe, like you say, so that it sometimes blocked the drain?

Looking back on it ... the clue was there when the oil pan was removed.

This was a short block and the customer had used about twice as much silicone sealer on the pan as was needed.

There was sealer that had oozed out from the joint where the gasket meets the pan and block.

Maybe when he was applying the sealer the "glob" of sealer must have found its way into the rear main cap past the oil slinger on the crank ... who knows?

very possible, if the silicone was up against the slinger it would be more like a scraper and scrape the oil off the slinger and it pools up and finds a way to flow...

[rally 1]

Pulled the engine.
Found the gasket between the block and flywheel housing basically not sealing on a portion of the gasket.

I did pull the pan, inspected the rear main drain holes, everything is clear.

Thanks again for the feedback.

Ken

[BILL WILLIAMSON]

I once saw a HORN cover, drippin' OIL??????
Bill W.