rear main seal leak

[BT911]

hi. i have a '88 3.2. the engine was rebuilt about 12,000 miles ago. on one of my oil change i used synthetic Mobil 1 and the rear main started to leak. i did an other oil change with a non-synthetic oil and the oil leak stopped. now i have the engine out and i want to replace the rear main but i've seen that there is 4 supersesions. on my rebuild i put part # 999.113.426.41 and it seems that is the newest one out. the seal is made by Kaco and it's black. my original one was light brown and made by Kaco as well. any ideas what would be the best one to put in for running with synthetic oil. thanks

[fred cook]

I would have to believe that either seal would do the job. However, it is important to seat the seal so that the sealing lip is not pressing against a spot worn by the previous seal. Also, use a seal installation tool to seat the seal evenly and without having to bludgeon it into place. You can make a seal installation tool out of a piece of thick wall pvc fitting that is the same size as the outside diameter of the seal. use some long bolts that thread into the crank flywheel bolt holes and use a flat piece of steel to tighten nuts against to pull the seal in evenly. There is a steel tool that does the job, but it is fairly expensive. The threaded rod that I used was not the correct thread for the flywheel bolt holes, but I rethreaded them using a die. Good luck!

[Zeke]

Originally Posted by fred cook

I would have to believe that either seal would do the job. However, it is important to seat the seal so that the sealing lip is not pressing against a spot worn by the previous seal.

That is the most important part of his post. If the current seal is installed flush with the case, install the new one so that it is proud of the case maybe .0025 "

If it were me, I'd just buy some Brad Penn.

[burgermeister]

Isn't that picture the front main? Or does the 911 carry over the front engine terminology, and call the seal at the tranny end the rear main, even though it is at the end of the engine that's towards the front of the car? A dumb question, but I'm curious. Edumacate me!

[BlueSideUp]

The phraseology seems a little backwards on a 911. The rear main seal is referring to the clutch end of the crank. The front main seal is at the pulley end.

I have a leaking front and rear main seal on my 2.2, I don't think you can replace the front main seal without splitting the case. It will leave about a 1/2 dollar bill size spot on the floor after a week.

[yelcab1]

You can replace both seals without spliting the case. You cannot replace the nose bearing seals without splitting the case, but you can seal it up with grey RTV properly done.

[BlueSideUp]

Man that would be great. It's a project prime for while-I'm-in-there-itis.

[Wayne 962]

Fred, that's an awesome tool, but I've never used one. I've always just tapped it in place and put a little bit of Curil-T on the outer surface (after cleaning the case very well). Works fine.

DON'T USE SYNTHETIC ON THE OLDER CARS - IT WILL CAUSE LEAKS JUST LIKE THIS ONE!!!

I say this in multiple places in both my 911 books...

-Wayne

[fred cook]

Here is the tool that I used to install the pulley end seal:





This is a pvc thick wall coupler using a threaded rod and one of the motor mount washers. Both front and rear seals press in easily, but I have had the seal spring pop off before because I seated a seal by hammering it into place. Also, you run the risk of cutting the rubber on the seal. Using the tools may be a classic case of overkill, but is easier than having to pull the engine back out to deal with a leaky seal!

[MobileWrks]

I do the same WAYNE.. Tap with a flat hammer. One thing i noticed after making the mistake.. I put the rear main seal in the same exact place it was before, and ended up leaking.(Minor crank groove) So now i make a habit to slightly modify tension on the spring, and install it about 1mm forward..

Deff a cool tool though..

[signature65]

Out of courisity.....how does curil T compare with Haylomar? I gotta do my rear main and fron pully seal soon.

[old man neri]

Originally Posted by Wayne at Pelican Parts

DON'T USE SYNTHETIC ON THE OLDER CARS - IT WILL CAUSE LEAKS JUST LIKE THIS ONE!!!

I say this in multiple places in both my 911 books...

-Wayne

My PPI said the rear seal was 'weeping'. Ever since I have been using a synthetic (elf brand) and have not had one leak anywhere. (Other than the blown oil pressure switch). But my car is an 88 and may not be defined as an 'older car'. From what I have researched the first synthetics use to cause the problem but later synthetics supposedly had all sorts of magical pixie juices added to them to prevent it.

-matt