Rear main seal..........yep, still leaks
 

Had a post of mine on 10-21-23 about my rms seal leak..........alot of good answers on what might be the problem..........so you dont have to read the thread, tried the best gasket seal, then the one piece bop seal, no idea on what was used on the 1st rebuild.

Im just trying to understand this a little better..............is it possible about some machining defect, or block issue why these gaskets dont seem to work one way or the other.

Pics show after running about 30 or so miles, about 5 drips after running, i clean them up.............couple hrs later another 4-5............this was from driving on Last sunday............monday about the same amount of drips...........tue on 1 drip as in pic...............wed , back to the 3-5 drips.......

My question, i understand it will drip while driving, but why does it keep dripping three days later while the motor isnt running.............

Im thinking maybe its something with this 455 block, and maybe not with the gaskets themselves...............any thoughts on this.

Big question for you guys with leaks.............this seem about normal for you also.............as of right now, i have 330 miles this year, and the dipstick is still reading full.............maybe im not losing all that much oil, lol..........who knows.

Not sure what im gonna do in the future, but thinking 3 strikes im out with this block ...............

Rich

forgot a pic................like i said, 4-5 drips , then check about 5 hrs later, the same............then check again the next day.............only one drip like in the pic..............then a few hrs later back to the 4-5 drips...............im gonna have to live with this because im not pulling the motor again.

I just find this strange with nothing running why all the drips...............the reason the drips seems all over the place was i drilled a few holes in the inspection cover, didnt want that getting on my clutch.

The drip in back im assuming is flying on the trans and dripping later.

Like i said, about 330 miles so far and dipstick still reads full...........im assuming i should get 600-800 miles before adding a qt............maybe thats gonna be the best i can do..........lol

Rich

You're 100% positive it's the rear main seal and not the pan gasket? The rear corners of the pan as well as the half moon cutout below the rear main is notorious for leaking. The factory pan doesn't help this any because there's no ridge to keep oil from climbing the rear wall up towards both the rear main seal and the pan gasket. This is why it continues to leak. Even moderate throttle application and moderate acceleration will see a wall of oil climb the back wall of the pan and seep into the gasket area.

I had the same issue with my 455 until I replaced the pan. It would drip, sometimes for days from a spot that led me to believe it was a rear main leak. When I had the engine out to replace the pan, the rear main was dry, but it was leaking from both rear corners of the pan and significantly around the half moon cutout for the rear main cap.

I opted for the 1 piece BOP pan gasket and spent a good amount of time with a ball peen hammer making sure the pan was flat. Even though the pan was new, the rear corners needed some massaging to get them flat and several of the bolt holes were concave and needed flattening. I then used a small dab of gray RTV at the front corners where the pan meets the timing cover, at the corners of the rear main cap and a light smear on both the rear main cap and that portion of the pan itself. I let the RTV set for a couple minutes, then bolted the pan up, making sure the areas that received a dab of RTV had a tiny pit smoosh out from the corners, indicating it had sealed those angles.

In my case, the engine went back in the car a couple days later, but I would wait a minimum of 24 hours to let the RTV set before putting any oil in the pan.

Also, make sure you do not over tighten the pan. It can be tempting to wrench down on this stuff in hopes of sealing it, but that bends the pan and actually pulls the rails off of the gasket surface, creating areas that can leak.

None of this matters of course if it is actually the rear main leaking. My point was just to illustrate that leaks on the pan itself can present as a rear main leak. Even leaks at the front of the pan. Because the engine is typically angled downward, plus the direction the car travels, leaks near the timing cover can travel along the crevice between the pan and engine towards the back wall of the engine where it will then creep down the back of the pan, around the transmission bellhousing, on to the starter and cause drips in those locations. You can spend a lot of time chasing oil leaks at the back of the engine when they are actually at the front!

I tried to fix mines with the two piece unit begrudgingly...still leaks of course

I've learned to live with it as I have never had a non-leaky pontiac 😑

I paid an experienced friend to both build and deal with the machine shop that was tasked with machining my 421.

He had already done several with the latest one-piece BOP Engineering seal and knocked it out of the park, he is the go-to guy in his Pontiac club for engine building.

150 miles later zero oil or coolant leaks. :thumbup:

We’ll see how it goes from here. :)

First picture installation of the crank and BOP seal by himself using an engine hoist. Second pic static testing of the main seal and oil pan sealing at the rear. Third pic on the run stand for break in and lastly my friend and his son unbolting the engine from the stand so I could bring it home.

Jason, you bring up alot of good points..............im not 100 % sure its the rear main, just going by the oil is all over the front of the flywheel and on the bottom of the inspection plate................the guy did a smoke test on the motor, said the only leak was at the front of the pan, which i guess 2 inches of silicone must have stopped the leak..........lol

Guess what im asking is what im showing in the pics about normal for you guys with some leaking issues................i guess i can live with this, not happy about it, but way too old to go messing around with this for the 4th time.

And whether im right or wrong about the rms vs the oil pan, the motor has to come out again anyways...............not sure what im gonna do, but so far the motor is running great, except for the leakage.

Rich

None of this matters of course if it is actually the rear main leaking. My point was just to illustrate that leaks on the pan itself can present as a rear main leak. Even leaks at the front of the pan. Because the engine is typically angled downward, plus the direction the car travels, leaks near the timing cover can travel along the crevice between the pan and engine towards the back wall of the engine where it will then creep down the back of the pan, around the transmission bellhousing, on to the starter and cause drips in those locations. You can spend a lot of time chasing oil leaks at the back of the engine when they are actually at the front!

Jason, just reread this again....................in the front of the pan is where the builder put the excessive amout ouf silicone on my pan.............makes you wonder where the problem is in the first place...............not sure what im gonna do except is watch whats going on..............hopefully this all works out ok

Rich

Check here too if you pull it back out. https://forums.maxperformanceinc.com...ight=rear+main

If it’s a a couple drips like you are seeing currently, I’m not certain I’d want to pull the engine to meaningful work on the pan. I’d probably invest in a decent drip tray instead.

Mine used to drip about double that amount. I lived with it for years, then took care of the problem when I had to yank the engine for something else.

Jason................this is the finest dirp tray money can buy..........lol, i dont even know where i got this from..................im gonna leave it like this for awhile..............thanks for the help, sometimes i worry about way too much stuff to worry about.

Rich

Maybe it's not the RMS leaking. Occasionally I've come across engine blocks that have porosity holes. I posted a picture of a block we recently repaired that looked like a seal leak. The best seal on this planet would never have stopped the leak. It acted just like a bad RMS, the oil ran down the pan and dripped off the lowest part.

The picture shows the rear of the block. The large hole is the other end of the RH side rear main cap dowel pin hole. The hole that was leaking is circled.

The amount you’re showing would bother me enough to fix it.

Have you tried UV dye to see where the leak is actually coming from?

I tried that last year, the black lite didnt seem to work all that well, will try again this year..........

Wanted to say thanks for everyones help............good points, thinking if i go about fixing this, im gonna try a different block, this is the 3rd time with this 455 and im losing confidence fast...........maybe nothing wrong with the seals, could be the block for all i know.

I guess what im having a hard time wrapping my head around, i understand it would drip while driving some, and a little when shutting down, but 2-3 days later without it running, i mean where is that comming from.........lol

Im not getting any younger, 73 this month, not sure i want to mess with taking this motor out again............have a great day guys.

Rich

On a lighter note, my mother who is 94 says, let me try putting that rear main in..................im thinking why not........lol

What a Mom!

:)

I'd also check the rear gasket area of the pan.
Was a cork gasket used on the pan 'half moon' section or rubber?

:confused:

Pontiac V-8 is among the most difficult engines period to get 100% leak free at the rear pan/main seal area. I consider myself pretty skilled and I am probably 50-60% absolutely leak free in that area. I mean not a drop of oil after lots of miles and hard driving. The other half do show some signs of weeping or an occasional drip or two on the ground when parked. There are just so many factors conspiring to make them leakers back there. 1. Not near enough fasteners holding that giant oil pan on. 2. A huge expanse of very thin sheet metal over the main cap area with no support and three different attempts to seal it, cork, and two lousy rubber seals. 3. The rear main housing bore is a complex shape and the cut is not accurate for size or diameter or centerline. 4. None of #3 is particularly important when using a rope seal because it will conform, but the rope itself has issues as we know. 5. Using the aftermarket seals is always worth a try because they are a dynamic seal. 6. The aftermarket seals have issues when the main cap and block groove are lousy though as mentioned. They are not very forgiving on the OD dimension and an out of round bore. So overall, it's not one of Pontiac's most endearing design features. Much like a Harley engine, Pontiac's like to mark their territory.

I know this is a longshot and probably not the issue, but what appeared to be a RMS leak on my newly rebuilt engine ending up being an oil filter housing gasket leak that evidently leaked and traveled south. Doesn't entirely make sense to me, but that's what the shop said and now has not leaked.

I think you really need to confirm where the leak is coming from. On my previous build I had a leaky pan, a leaky two piece rear main AND a leaky oil filter adapter due to a crack. It was a mess under there. Oil can also leak down from the valve cover gaskets or distributor. Lots of places it could be coming from besides the rear main. Try the UV dye again or pick up a smoke machine.

As a band aid, if you really don't want to pull the engine, you could try a Wagner dual flow PCV. It obviously won't help if it leaks while sitting, but it may minimize leaks exacerbated by crankcase pressure at run time.

Wow...mom looks great for 94. You're both lucky to have good genes.

[QUOTE=johnta1;6507724]What a Mom!

:)

I'd also check the rear gasket area of the pan.
Was a cork gasket used on the pan 'half moon' section or rubber?

Thanks John, for the oil pan i used the one piece from bop, was gonna cut the part off that went over the crank and use a piece of cork for the cap, thought this would work as is.

Im gonna take Verdoro 68 advice, will try to dye and blacklite and see if i can get it right this time..............on the smoke test the builder said he did this and the only place it leaked smoke was on the front of the oil pan..........there he threw enough silicone on it..........i can run my finger up where he did the work, still get a little oil on my finger...........so much for the smoke test.

Dont know if its true or not...........read a few reports about the seal not leaking to let smoke by, but oil will leak, so not sure on that deal.

So far my plan is drive the car this summer, hopefully i can buy a motor somewhat like i have now..............just dont feel confident using this 455 again.

At least one good thing came out of this, i had the motor re-ringed, at least im not blowing smoke all over the place.............just dripping it.

Rich