I am in need of replacing my rear main seal because i am leaking oil out daily by the quart lol. i was wondering if i had a one or two piece rear main seal? i have a 1987 pontiac firebird with a 305, carbuarted, t5, vin H

THANKS

 

Thats a transition year. Id suspect that it probably has the one piece, but you can tell for sure by the block casting numbers, or by simple inspection. If you pull the inspection cover off of the bottom of the trans, you can look in and see what it is. Older two piece has a small counterweight on the back of the crank shaft that the flywheel bolts to while a one piece just looks like it has the flywheel bolted directly to the motor. With the later one piece the flywheel itself will have a small counterweight attached, while the former has none.

If its a two piece, replacing the seal will be more difficult. Usually only the lower seal can be easily reached, and then it requires the removal of the oil pan. The one piece will only require that you pull the trans back to replace it. Its held in with a retaining ring mounted around the back of the crank.

Its also possible that its the oil pan itself leaking.

 

86 was the 1st year for the 1-pc; if your engine hasn't been swapped, that's what it'll be.

RMSs almost never are the biggest leak on an engine. I'd avoid the tempation of going straight for the mother of all leak repairs, and instead do a little investigation.

Take the car to the quarter car wash. Stop along the way and buy about 3 cans of Gunk Engine Bright, or the store equivalent product; you're looking for diesel fuel in a spray can. Take some WD-40 and a screwdriver for your dist cap, just in case. Might even be a good idea to take your Rhino ramps with you.

WHen you get to the car wash, park the car up on the ramps with the engine right over the drain grate, pop the hood, take off the air cleaner, and wait about 10 minutes or so. Then hose the engine down with the diesel fuel. Top, bottom, sides, from the front underneath, from each side underneath, and so on; the goal is to soak every surface of every part of the engine, and wash the accumulated schmutz of the last 25 years off of it, so you can see what you're doing. The goal is NOT to just stand above the engine and spray what you can easily see and get to; do a little WORK on it. (sorry for swearing at you) YOu want to get that stuff into every nook and cranny; on the sides of the block, sides of the oil pan, the K-member, and so on. Should take AT LEAST one whole can, probably a can and a half. Let the stuff soak in for about 5 minutes or so. Dose it again. Hit the air cleaner and any other parts you might have removed. Wait about 5 more minutes. Start putting quarters in; put in about 6 minutes worth; set it on "engine cleaner" if they have it, "tire & wheel cleaner" or "presoak" if they don't. Again, get it from every angle. Lay on the ground and get up under the car just like you did with the degreaser. Don't forget the air cleaner. Let that sit for a couple of minutes. Then put in more quarters, and go at it with the "wash" and then the "rinse". Finish up with the "wax" to help keep everything from rusting so much. Avoid spraying directly at the distributor or into the carb (you can wash the outside of it if you want) or any of the electronic sensors, as much as practical; a little water on them won't hurt, but you don't want to force water into them.

If the engine won't re-start, pop the dist cap off and use the WD-40 on the inside of it. Same for any other sensors that act up.

Now, drive home, and inspect it CAREFULLY to see where the oil os actually coming from. Remember, it runs DOWNWARD; just because you see it at the bottom, doesn't automatically mean it CAME OUT FROM the bottom. Odds are, your leak is ACTUALLY the valve covers, oil pressure sending unit, oil filter, rear intake "china wall", or if your smog pump has been hacked off, the upper bolt in the front of the block on the pass side where its bracket used to be.

It's SO MUCH easier working on a CLEAN car, and SO MUCH easier to actually SEE where it's leaking, when you're not fighting an inch of accumulated crud on everything.

 

I would also check your valve cover/ intake gaskets and oil psi gauge/switch