Rear engine oil seal leak

[Mark Strang]

Making a bit of progress on TC7801. Got it running finally and tuned up. All is well and it runs very well except for one big item. The engine had been rebuilt 20 years ago and was a stalled project when I bought it. It had reportedly been rebuilt and test run which I believe to be true based on new core plugs and carbon in the exhaust manifold. I removed the rear cover on the head and it had virtually no buildup indicating a head job of some sort. After running it for various periods of time, I noticed the dreaded pool of oil under the bellhousing from the drain hole. Seems to me that the rear seal is shot either from a bad installation job or from sitting too long. Is there any way to fix this issue without pulling the engine and tearing it down?

[Steve Simmons]

Could be poor clearance on the original scroll seal, could be a bad Moss seal installation, or could be a bad job sealing around the gaskets at the rear, which is pretty common. No matter what, there is nothing to do but take it apart or deal with it. If it isn't horrible, maybe use a catch can?

[Duncan M]

Normal amounts of blow-by can force oil out the rear engine scroll seal while the engine is running, if the vent in the valve cover or vent/draft tube are no longer in place--as original. Some of the fancy aftermarket aluminum valve covers and aluminum rocker covers to not have vents. Some do. Need both vents.

Normally, a spoonful of oil drips out after shutdown with the original type scroll seal. Catch cans can be easily crafted to catch that spoonful on shutdown

[stephen stierman]

Just for some information, when I rebuilt the engine of TC2911 which leaked a pie plate of oil on shutdown, I used the Moss seal. These things require very exacting installation to work and really need the speedy sleeve installed which I did not do and my installation was not successful. I think the clearance between the flywheel and sleeve unit was too close also, although the crank end float seemed to measure ok.

I went back to the slinger. There are several articles describing how this works and how to achieve an almost leak free installation on the web and probably on this site. I went through these and with some careful filling and fitting and running the engine on my test stand for an hour got very good results. Once in the vehicle and in use I would get a drop or two after a long run, NO spoonful or No catch can needed. The crank had been turned .010 under with new bearings upon rebuild but no fancy line boring was done. It is possible to still get a good result by carefully installing the slinger. I sold the car after about 20,000 miles of driving and the couple of drops from the rear main had not changed.

[Mark Strang]

Stephen, I'm inclined to go the slinger route but it still sounds like the engine needs to be disassembled. Is that correct?

[stephen stierman]

Mark, you do have to remove the sump, flywheel etc. to get access to the rear of the engine. The rear main cap will be removed, but the crank really does not have to come out. You are basically setting this up so the alloy slinger is very lightly against the crank indicated by the transfer of engineering dye or lacking that slow drying thin paint that will transfer. I left the drain pipe off and drilled a couple of extra drainage holes in the valley of the main cap to facilitate oil drainage.

[Mark Strang]

Thanks for the info. I guess I'll just have to pull the engine and take a peek at what has been done. That will dictate what to do next. Hopefully I can get at it in the next couple of weeks. We leave for several months during the summer. It might not get attention until this fall. I really don't want to think about it all summer not knowing what I'm up against. Life just seems to mess up fun things!

[stephen stierman]

I feel your pain so I built a test stand to run the engine on prior to putting it back in the car and ran it for a good long time.

[Mark Strang]

Well, things are interesting. I kept wondering how could so much oil could be coming from the rear seal during short run times while tuning things up. The builder couldn't have screwed up the seal if everything else was good such as compression at 150 psi etc. There had to be more to the problem and a reasonable solution even though it was sitting idle for 20 years. Something was pushing the oil past the seal. I took my bore scope and introduced it to the breather pipe and saw nothing but the cork gasket and as the view was somewhat limited as it was, the gasket appeared to be tight to the pipe. I took the tappet cover off and there was an imprint of the pipe in the gasket. I cut a hole in the gasket about half the size of the tube and put it all back together. I ran it for about 15 minutes with no oil coming from the seal! Apparently the gasket just was up against the breather pipe so there was no venting and the crankcase pressure pushed the oil past the seal. I never checked on the two TD'S that I have for the amount of pressure from the breather pipe. It is a surprising amount of volume. I'm curious now about the pressure in those cars. Now I just have to tear it down again and install a new gasket and fix a few other minor oil leaks. Hopefully tomorrow morning there will be nothing more than a few drops on the floor otherwise I'll be back on the forum. I'm thinking that at the risk of a bit of oil coming from the pipe I might make another hole in the gasket or weld on a device to the pipe inlet to ensure that the gasket and the pipe don't interfere to make sure there is clearance for air to move.
Stephen, I'm doing a ground up restoration and am doing the engine work in the chassis without the body in place. I've attached a photo of my "test stand". I've never sent a photo on this site so it might not come through.

[Steve Simmons]

Good news on a simple solution. The chassis looks great! I wish I was that far along on the two TCs sitting in my shop, but they are very slow going.

One note, the holes in the gasket are at the four corners to keep oil splash and vapor away from that pipe, so you don't get oil dripping out of it. I think the best solution would be something to hold the gasket away rather than a hole right at the pipe, although that seems like a great short term remedy. Some people put spacers on the inside of the three tube nuts to hold the gasket away. a baffle of some sort at the pipe would probably be even better. Keep us posted.

[stephen stierman]

Excellent Mark, hopefully you have found an easy fix and can move on, looks great.

[Mark Strang]

I'm going to study how to keep the gasket from sealing the breather pipe. Lots of options. The new hole in the gasket didn't seems to allow any oil to escape through the tube but I really don't want a direct path to the outside. I'll figure something out. I'm "breathing" a sigh of relief knowing that I don't have to break down the engine. The fix will be simple.

[i.thomson]

this might help:

https://ttypes.org/keeping-oil-in-an-xpag/

Ian