Oil Leak: Rear Main or Gallery Plugs?

My 1971 Pantera has an oil leak at the back of the motor. It only leaks when the engine is running. When I come back from a 5 mile test run it makes a 6 inch puddle on the garage floor. Once cleaned up there is no oil leak and thus it looks like it happens due to oil pressure. I have seen this problem before with an improperly sealed oil gallery plug. If that's the case on my 71 Pantera can I fix it by just pulling the transaxle and bell housing? Or could the problem be in rear main seal which probably requires pulling the engine?
Original Post
I bought the car in February of this year. The motor was probably rebuilt about 30 years ago and has between 5,000 and 10,000 miles on it. It has mostly sat for the last 25 years per the previous owner. It runs quite well. I am hoping to avoid pulling the engine and tearing it down. But the oil leak needs to be fixed.

I have already replaced the head gaskets due to water in the oil. I am hoping that the sealant on the gallery plugs has dried out. There is a lot of pressure on the plugs and they will leak profusely without a good seal when the engine is running. I do not have any experience with rear main seal leaks.
Steve, the rear main seal is replaceable without pulling the engine.... IF your Pantera has been updated with the factory removable rear crossmember that runs under the engine, so you can remove the oil pan. '71-'75 Panteras used a crossmember that was welded in place which requires engine removal to get at the pan. And for the preferred oil pan- an Aviaid 10-qt, the e-brake bracket must also be cut free and made removable (with a 4" long section of angle-iron & some metal screws).

But if you do this and your car is unmolested from as-built, you may find that the '71 factory seal was a rope-seal, which was difficult for many to work with & was replaced in the early '70s by Ford with a 2-piece neoprene seal. Now there are one-piece seals available of neoprene or low-drag teflon, but those require the block & rear cap to be remachined. And depending on how many miles your engine has, seal wear on the crank journal may keep ANY seal from stopping the drips. Good luck- J DeRyke
head gaskets already & now this, i think i know what i'd do

quit -ing around and nip the next catastrophe in the bud!

maybe put dye in the oil for verification before / after the engine comes out, these 2 products from different sources are pretty reasonable

https://shop.advanceautoparts....mPD_BwE&gclsrc=aw.ds

https://www.oreillyauto.com/de...e/tp30900601/4748778

my experience s limited to installing rear mains & oil pan gaskets on and engine stand or shop floor out of the car, i don't think i'll ever try doing it myself any other way. even with a lift it's shady doing it w/o removing the crank from the block IMO. i know guys do rear mains in the car year in / year out but those are booking hours shop rate mechanics, just not the way i roll
BW,
On my 72 Pantera I have already done the conversion to the removable crossmember. I will do the same on the 71 if I replace the rear main seal in the car.

4V,
I cannot agree more with your suggestions. Replacing head gaskets in the car is horrific compared to the same task on an engine stand. The same probably is true for the rear main seal.

But I do have a question about rear main leaks. Do they leak in the way that I described at the beginning of this thread? That is, the leak happens when the engine is running due to oil pressure.

Also, below is a thread describing how to replace the rear main seal in the car. However, I will be spending more time on diagnosing the exact source of the leak before doing anything.

http://pantera.infopop.cc/eve/...311078956#6311078956
Steve, If I were you I would pull the trans, clutch and flywheel out and see whats going on. Work from there. You could even pull the distributor and insert a drill driven pressure tool to simulate the engine running. Chances are you will see where its leaking once the flywheel comes off.
Are there gallery plugs at the BACK of the motor?

I didn't recall there being any, but my recollection is fuzzy....

I thought the two were up front, in the timing chain area on the front of the block.

ANSWER: Yes there are. Now that a person thinks about it, it would be a lot harder to "blind drill" 2 1/2' holes in the block vs going straight through. I guess I never gave these plugs much thought.

Also there is the cam plug in the back as well.

You live and learn.


Thanks -

Rocky

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There is a small sharp pin in the seal groove of the #5 main bearing cap, intended to secure the OEM rope seal. Most folks replace the rope seal with a neoprene seal. When doing this the small sharp pin must be removed, and a dab of sealant should fill the small hole the pin was pressed in.

If the pin isn't removed it distorts the neoprene seal and creates a leak. If the pin is removed but the hole isn't sealed, this creates another leak.

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