Rear main bearing seal leak sealer - detrimental to engine?

[Oliver S.]

Beside my '65 Corvette I own a '68 Pontiac Firebird (2bbl + 2 speed auto - nothing special). The engine is the original one - most probably never out or overhauled. Ever since I have been owning it the engine has been leaking - most probably the rear main bearing seal. Since I don't drive that much with it I haven't addressed this issue. Of course, the best option is to replace it. However, I fear this ends in a bigger endeavor since the bolts and screws might shear off because the engine has to be lifted or removed - the oil pan can't be removed completely due to insufficient clearance with respect to the front suspension.
Normally I would never think about adding additives to the engine oil. However, in this special case I'd like to ask if a main bearing seal leak sealer would jeopardize the engine as a negative side effect. If not, maybe I would give it a try - despite being a temporary fix in terms of mileage - which would result in a couple of years for me if it works. What would be a good brand?

Oliver

[Joe R.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

Oliver,

I've never heard of a product that would fix a rear main seal leak. That don't mean that there aren't 50 on someone's shelf.
I would never consider using a sealer in the oil because it's just too easy to replace the rear main seal. Drop the pan, remove the oil pump and rear main bearing cap. Replace the seal and you are on your way.
There are videos on You-Tube to accomplish this task.

JR

[Joe L.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

Beside my '65 Corvette I own a '68 Pontiac Firebird (2bbl + 2 speed auto - nothing special). The engine is the original one - most probably never out or overhauled. Ever since I have been owning it the engine has been leaking - most probably the rear main bearing seal. Since I don't drive that much with it I haven't addressed this issue. Of course, the best option is to replace it. However, I fear this ends in a bigger endeavor since the bolts and screws might shear off because the engine has to be lifted or removed - the oil pan can't be removed completely due to insufficient clearance with respect to the front suspension.
Normally I would never think about adding additives to the engine oil. However, in this special case I'd like to ask if a main bearing seal leak sealer would jeopardize the engine as a negative side effect. If not, maybe I would give it a try - despite being a temporary fix in terms of mileage - which would result in a couple of years for me if it works. What would be a good brand?

Oliver

Oliver------


It will not harm the engine but it won't seal the leak, either.

[Domenic T.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

Oliver,
Ray & Joe are right but I have used ATF in the oil, about 2 qts to 3 qts oil. That will swell all the seals on a buba car with good results, Front, rear? and valve guide seals. That's why the automatic dip stick seal (O-ring) leaks in about 6 Months if you use a regular O-ring and not a ATF O-ring that is compatable with ATF. Another one was adding a bit of dot 3 to the oil. Once the seals swell up and the leak stops then change the oil and it will live for a long time.
Had the whole family out of town on X mas eve and my power steering pump blew a seal. My nephew owned a gas station but didn't have any fluid. SO he added dot 3 so I could at least get to the freeway without the problem. NEVER EVER leaked again. Lucky, right, but ATF could do it. Now, the rear main has a bunch of pressure so it might not work, but if it doesn't then you are where you are now.

Dom

[Mark E.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

R&R of the oil pan and rear main seal is a simple process on C2/C3 Corvettes (C1 too??), so the decision to just renew it is an easy one.

For other cars where the pan sits above a cross-member, renewing the RMS can be more work. But often it can be accomplished by removing the motor mount through-bolts, and jacking the engine block a few inches. Check the FSM.

Be thankful you don't own a mid-engine Ferrari...

[Jim D.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

Most of the time, the rear main seal replacement is not a big deal. I've done several with the engine in the car and never had a problem. That being said, while doing a body off restoration to my small block 65 coupe with only 50K miles, I decided to reseal the engine. With the engine upside down on an engine stand, I figured it would only take a few minutes to change the seal. I knew I was in trouble when I removed the main cap and had to chisel out the seal in pieces. There was no way to remove the upper portion by tapping it out. I ended up having to remove the crank and that half of the seal came out in several pieces as well. For some reason, both halfs had become "welded" to the block and main cap. Just another of those 10 minute jobs that take several hours.

[Paul F.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

Oliver,
It looks like your question is regarding your Pontiac engine (I assume it's a v8). If it's never been apart, your engine has a two piece rope seal which is most likely made from asbestos. Since asbestos is a mineral, it's not going to swell like a neoprene or rubber type seal by using a stop leak additive. I don't know of any way to affect the leak, other than replacing the seal. And you're right, pulling the pan on the Firebird requires lifting the engine up 4 or 5 inches, not easy. As you said, a bigger endeavor...
Paul

[Mark B.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

if it uses a rope seal adding leak seal won't help. if its a rubber seal it can soften and expand, but its a temporary fix as the softening agent also make the seal wear out faster.

[Joe L.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

Oliver,
It looks like your question is regarding your Pontiac engine (I assume it's a v8). If it's never been apart, your engine has a two piece rope seal which is most likely made from asbestos. Since asbestos is a mineral, it's not going to swell like a neoprene or rubber type seal by using a stop leak additive. I don't know of any way to affect the leak, other than replacing the seal. And you're right, pulling the pan on the Firebird requires lifting the engine up 4 or 5 inches, not easy. As you said, a bigger endeavor...
Paul

Paul------


Yup, Pontiac V-8 engines used a rope type rear main seal from the very beginning right up until the time the last one was made in 1981.

[Mark G.]

Re: Rear main bearing seal leak sealer - detrimental to engine?

If you go for it, I'd use a neoprene replacement seal. The last Pontiac engine we did, we got it here:

https://www.bopengineering.com/

Yes, the engine has to be lifted to remove the pan. As we all know, a simple job like this can and does turn into a project.