Hole in rear of oil pan
 

I tried to find more information on this, but I couldn't find any. I have had a small oil leak since I reassembled my engine. It is a 1.8 from a 1997 and was bored over, hot tanked, and decked.
The leak was a few drops after hard driving with a t2560 at 12psi. But now I am running an EFR6758 and the leak has become significantly worse. The oil appears to be coming from the transmission weep hole and clutch fork shift boot. I have replace my rear main seal twice now, and the second time I used an OEM Mazda seal with FM install tool. I have also replaced my oil pan gasket and the leak persists. So I am now replacing the steel(?) oil galley plug with an OEM Mazda brass plug.

I have also replace the CAS o-ring and I am certain it is no longer leaking(back of head and tops of trans is dry).

But upon looking at the oil pan, I spotted a hole in it. Is this normal?

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Got the same hole in mine. That leak is almost always the CAS though, rarely the rear main seal. Have you modified your valve cover PVC passages to help reduce crank pressure?

Yes, I have replaced the CAS O ring twice and I used an anaerobic sealant on the cap. It stopped leaking once I used the sealant.

Thank you Curly, I checked my old motor in the daylight and found the same hole. I can't believe I never noticed it before.

I replaced the galley plug the machine shop used. This is a comparison of he plug and the OEM Mazda part. The plug came out very easily.

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The brass plug has a tapered end and the block has a machine surface for it to mate to. I added a little anaerobic sealant and made sure it counter sunk a little.
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Sorry to revive my old thread, but I am at loss for how to proceed. I still have oil leaking out of the transmission weep hole and out the clutch fork shift boot. I have replaced the CAS O-ring and have made sure the back of head and top of the transmission are completely dry.

I have replaced the rear main seal twice, the second time with an OEM Mazda part and all installations have been done with the FM installation tool. I have re-sealed my oil pan, rear main seal holder, and just last weekend, I replace the steel plug in the oil galley with an OEM brass plug. The car continues to leak oil as if I haven't replaced anything.

Is there something I missed? Can I start the engine without the transmission to spot the leak(I can cut a bracket out up my old broken 5 speeds trans to make a starter holder)? Or is there a way to pressurize the oil system to find the leak? I have tried dye in the oil, and since the leak hits the flywheel, it sprays oil everywhere in the bellhousing.

Any scratches or grooves on the rear crank?

Did you use sealant on the flywheel bolts?

Are you certain it is engine oil and not gear oil, did you change the front seals on the tranny?

I always use locktite blue on my flywheel bolts, but even the new bolt in, "which is the right bolt" or something like that, has sealant or locking compound on the threads from Mazda. You can see in there with the bolts removed.

I will check for scratches on rear of the crank as soon as I drop the transmission.

I also always used blue loctite on the flywheel threads. I stopped using red loctite over the last few months, as this is he 6th time I'll be removing the transmission.

Thank you for the suggestions.

Blue loctite is not oil resistant. You need a thread sealer for the transmission bolts.

Thanks for the tip, I will use the proper sealant. The trans will drop this weekend and in will go another oem rear main seal. Provided the crank seal surface is in good condition.

"Are you certain it is engine oil and not gear oil, did you change the front seals on the tranny?"

Sorry I missed this before, I have replaced both seals on the transmission. The fluid the is leaking does not smell like gear oil.

I will continue to update this thread, unless it becomes annoying to anyone. Thank you for all your suggestions.

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I've never noticed the nicks on the surface. How borked is my crank?

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Did you modify your valve cover to allow it to relieve more pressure? I think curly suggested that upthread. That's next for me as well.

Those look pretty deep. You could try knocking the high spots down with some emory cloth and hoping for the best. However if my experience with a scratched up cam seal has taught me, it doesn't take of a scratch on the sealing surface to cause a good sized leak. I would say next time use a soft faced hammer or rear main tool to install the seal. It looks like a screw driver (or punch) with a steel head hammer was used to drive the seal in based on the gouges and impact impressions on the edge.

YA, THAT SEALING SURFACE LOOKS ALL KINDS OF 'F'ED UP

I have modified my valve cover to allow for more crank pressure. I have also removed the pcv valve and both valve cover ports are going to a catch can.

I think the previous owner did used a screw driver to remove the old seal. I once asked him how much was a engine gasket kit for a rebuild, and he said he didn't use gaskets, just a bunch of rtv.

I noticed when I was removed the FM tool with an electric impact gun the bottom the rear main seal holder moved. I don't think the seal was at the proper depth on the bottom. I used a wooden dowel and hammer to tap it into place. I then used the FM tool to verify I reached proper depth. Hopefully this was the issue, I will start the car soon.


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Got it! No more leak! Lesson learned, after you install the rear mains seal, use the install tool as a "depth gauge" to make sure the seal is in the right location.

Thank you for all your help.

awesome dude. probably a big relief.