Inliners International Forums General Discussion Engines Rear Main Seal

My rear main seal is leaking, and I'm debating doing it myself, or having a shop do it. I have a '68 C10 with 250. Normally I would do this myself except you have to jack up the front of the motor in order to get the oil pan out. Any ideas on where to jack the motor up at? Will I have to drop the tranny(manual) in order to jack the motor up? I don't have an engine hoist. Also, I've looked at the Tech Tips section on the Stovebolt site and know how to do it. The only hitch is, I don't know which seal I have. Wick or neoprene. Any ideas? One other thing. I remeber that I had to fight to get the oil pan back on, because none of the bolts would line up right. Any special ways or steps to bolt the oil pan back up without moving the gasket. Thanks in advance. John.

After taking the bolts out of the motor mounts, you can jack up the motor with a block of wood under the harmonic damper. Put a couple of 2x4's between the motor mounts and the frame brackets for support and to keep it up high.

The 250's came with neoprene seals.

If your pan is tweaked to the point where the bolts don't line up, you'll probably need to sight along the rails and see if there is any way that a judicious application of a BFH will straighten it up. Also, I've had to use short studs a couple of times in the end holes (5/16") and 1/4" ones near the center of the pan rail in order to get it all to line up. Actually, most of the factory GM engines after about '88 have studs in those end holes. You can certainly leave the studs in there instead of taking them out and putting in the original bolts.

You can use a light application of 3M weatherstrip adhesive (aka "gorilla snot"), or some silicone to hold the new gasket up on the block. Personally I prefer to paint the block and stick the gasket right onto it. Use a rag and brake cleaner to wipe down the metal before painting. When the paint has dried enough, it's a great glue and sealer and will not allow the gasket to shift while you're putting in the bolts. Those studs I talked about will help you to line up the gasket when you stick it to the paint.

The only other thing I'll suggest is to jack up the motor and drain the oil overnight before you pull the pan the next morning. That way you'll get a LOT less oil drips on your face while working under the motor.

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David
newbie #4153

just a six--Thanks for the info, that helps alot. I hadn't even thought about studs. Do you have any suggestions for the front and rear oil pan seal. The last one I put in shifted and leaked really bad. Thanks. John.

Yeah, I do have some suggestions.

1. Don't use any sealer or glue under or on top of the end rubbers. Make sure you clean the surfaces very well with brake cleaner, and they are dry when you begin the assembly process. ONLY put a little dab of silicone on the ends where the cork gasket meets the rubber seal, and try to put some of the dab between the materials too. Keep in mind you're going to put some paint on the block as a sealer, right?

2. Install the front piece first. Depending on which pan and front cover you have, there will either be bolts through the rubber piece (early style) or no bolts (late) with little tits that go through small holes to retain it. Chances are, you will only be able to purchase a gasket set that has the late style rubber. If you have an early cover, use a hole punch of some type to poke holes through the rubber on 2 or 3 of the holes. Space them out evenly, as you don't need all the bolts. If you don't use any bolts on the early style cover, your front main seal WILL leak due to warping and deflection of the front cover.

3. Install the side rail gaskets second, as they overlap on top of the front rubber and go underneath the rear rubber.

4. On the rear piece, use a very small screwdriver to tuck the tips of the seal down into the notches in the main cap. Also use the screwdriver to carefully push the rest of the rubber into the wide groove in the main cap. You may not be able to get it to lay perfectly flat into the groove. Don't worry about that, as they are made a little long to ensure good crush when you tighten the pan bolts.

Good luck, and have fun with it!

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David
newbie #4153

P.S. edit: I forgot to say that you need to pull the little tit rubbers all the way up through the holes on the front cover or else cut them off. If you don't remove the harmonic damper, you may not be able to get to the tits to pull on them with a pair of small needlenose pliers or tweezers.

[This message has been edited by just a six (edited 07-10-2003).]

just a six--Thanks again. No, unfortunately I'm not going to be using paint right now, but I will probably use the gorilla snot and some studs. I have the late style cover that uses a seal with the tits. On this, are you saying just to make sure the tits are pulled all the way down into the holes in the pan? Also, what are your thoughts on the difficulty of the rear main seal? Thanks for all the help. John.

No, the tits pull upwards to attach the rubber to the front cover. With the balancer on the crank, it's tough to get behind it to pull all the tits through. If you can't get to the ones in the center and don't want to remove and reinstall the balancer, cut them off so they don't get smashed between the cover and the pan lip. They can make a hollow pocket that oil can get past and leak. Leave the ends ones on and install them properly so the rubber is located in the right place. As long as you are careful and slow, are using studs to line it all up and NO SILICONE, the end tits should work fine to retain it. Uncured silicone is a great lubricant, and it'll allow the rubber to slide every which way as you tighten the bolts.

As far as the rear seal is concerned, it's very straightforward. After you've installed the upper half of the seal, use a TINY bit of hylosil/hylomar sealant or quality silicone smeared on the metal between the block and main cap. DO NOT get any on the rear seal. This is just insurance against oil wicking through the metal-to-metal contact. Don't forget to torque the main cap I thought I forgot to do that once, and tore open a 460 Ford only to find out that I HAD done it

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David
newbie #4153

just a six-- You just have all the info that I need. One more question for you. What type/size studs do I use? Should I just use studs that are threaded the same size all the way down? What I mean is, should I use a stud that has only one thread size on it, or should I use a stud that has 2 different size threads on it? Thanks for all of your help. John.

hello..

[This message has been edited by LeeLites (edited 08-07-2003).]

What kind of studs you use isn't an issue. You can use the type that have a shoulder in the middle so the only screw in so far or you can get some threaded rod and cut off your own. Those will need to be threaded in all the way until they bottom in the hole. just make them long enough that you have about 3/4-inch of threads sticking up from the pan rail so you can get the nut started on it.

As far as size of studs, I prefer to always use the same size on both ends. If it's 5/16 threads in the block, it's 5/16 threads sticking up for the 1/2" nut.

If you have the time to let it sit and cure, you can do what Lee suggests. But the entire issue is moot if you don't use but a TINY dab in the first place. Remember, the gasket's job is to seal, and they are very well designed and perfectly capable of doing the job. When you put silicone on them, you are doing something the designer/engineer never did, so are modifying how the materials behave. You are only trying to fill any TINY gaps that MIGHT occur between the rubber and the cork gaskets. You are NOT trying to put enough silicone on there to replace the gasket. It's insurance only.

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David
newbie #4153

Thanks both of you for all of the advice. Y'all have been a great help, since this will be only the second time I've installed an inline 6 oil pan. The first time I almost hit the thing with a BFH. I think it should be relatively with all your advise. Thanks again. John.