Rebuilt engine, rear main leaking , viton seal
 

Just had my engine rebuilt, 3 months back, maybe 300 miles and leaking from the rear main seal. Machine-shop used 1 piece viton seal. I asked them what the deal is and i get.. well sometimes the never leak and sometimes they do.. what is the machine-shops responsibility in this? I know they wont pay to r&r the engine, so whats standard protocol?
Also when i replace it do i use a two piece seal? Not interested in removing the crank etc., very frustrating!!

One piece works great and i've had good luck....I would say one of the best seals out there.
I have used many seals including a Caddy for a stock 455 crank.
What crank are you running?
I don't think your going to be able to remove the seal without lifting the crank some.
I usually do a tilt test with an engine crane to test the seal for leaks.

Possible it's not the seal itself but the joints where the pan meets the seal and the block.

Your going to atleast need to drop the trans off and flexplate, then spray out the whole seal area with Carb cleaner to dry it out and then really jack up the nose of the car and remove the oil filler cap.
Then you will likley see where the oil is really seapping from.

Hopefully is from around the OD of the seal or the pan gasket area and you will be able to spray it dry again and then pack it with gray form-a- gasket and let it set up for 2 days and the reassemble with the trans out and start it to see if your golden .

I chased this oil leak for 6 years and pulled the engine 3 times before i found it. Make sure you check this! https://forums.maxperformanceinc.com...d.php?t=471237

Most Rear Main leaks....the front of the flywheel/ flex plate will be wet from the oil being slung. So I would clean it off really good with a spray Brake Cleaner, and run it and make sure it really is. Its a tough area to see, if its the oil pan gasket, rear seal, or the seam between the black/ main cap. I think the Machine Shop would be obligated to pay/fix the repair....If they supplied the seals / gaskets.

Recheck oil pan bolts gasket can shrink from heat cycling and can seep oil check easy stuff first before going for the big stuff

I agree to verify that it actually is the seal and not the pan or something else.

Using lip-type seals on factory cranks is hit and miss. Factory cranks have serrations cut in them to help the rope seals work correctly. Sometimes they are cut pretty deep and if the lip seal lines right up on them they will leak every single time.

I always do a mock-up with a lip type seal before deciding whether to use a rope seal instead. For most engines I've done with factory cranks I've used the Best rope seal and never had one drop of oil get by one. For aftermarket cranks I always use the Viton two piece seals (custom fitting required), and never had a leak with one of those to date either.......Cliff

Stock 421 crank

I prefer mineral spirits applied with a spray bottle over using brake cleaner. It pretty much leaves the paint alone but does a good job of attacking oil and dirt.

Not foolproof, but if the oil is on the flexplate/flywheel and the crank flange is dry after cleaning and running the engine, then the leak probably isn't at the seal lip. I pulled one engine down to correct problems from a previous shop's build and someone had filled the bottom of the groove with silicone before dropping in the one piece seal. Instead of the seal displacing the excess silicone, it distorted the seal with pockets of silicone holding it away from seating properly and allowed the seal lip to pull away from the crank in some areas.

You have to be careful with flattening the area where the main caps register. It's fine to find and remove particles that ended up there after machine work. If it is the actual cap or block surface and the line hone was completed with this rough mating, then removing material is going to tighten up bearing clearance. Bearing clearances are a little less than the width of a human hair and you really don't want to be smoothing bumps out unless you plan on a new main journal line hone.

For these tough situations I strongly recommend using an EVAP emissions smoke machine to verify the exact location of the leak. You can do this with the engine in the car and no damage to paint and so forth. Remove transmission and flexplate or flywheel, hook the smoke machine to a valve cover and let it smoke away. In 30 seconds to a minute the exact location of the leak will be very visible. You can tell right away if it is the main seal, rear pan seal or some other unknown leak source like the rear of the valley cover, distributor and so forth. Then you know 100% for sure what needs to be done to fix it. These tools are pretty expensive, so possibly you can borrow one from a good independent shop or rent one for the day. Virtually every new car dealer has had one of these machines in the shop for 20 years or more. Good luck with the diagnosis and repair. BTW, if the stock 421 crankshaft had the serrated seal area for the rope seal, that has to be polished to a very smooth surface finish to allow the Viton seal to run leak free on it. If it was left untouched, it has possibly ripped the lip of the seal.

Great advice!

Affordable smoke machine:
https://www.amazon.com/STINGER-Smoke...90603233&psc=1

For 150 bucks before shipping I'll lend you my neighbor, he's a endless perverbal smoke stack with his two pack a day addiction, lol!

I think I would try find the leak first by draining the oil out, pouring in a gallon of WD-40 with some blueing dye added to it and then jack way up the nose of the car and do what I suggested to trace the leak.

What do you think wd-40 residue will do on your bearing surfaces?

Nothing once you drain it out, add new oil and then pull the plugs to allow cranking of the motor for 20 seconds.

I, too, have leaks. Thanks for great advice!

I never knew that and was just over to my machine shop and he showed me where he actually sealed that ,he says that they always do that.he put a special red sealant in between there and not just silicone I guess

I always use an anaerobic sealer like green Loctite to seal the main cap to the block. Silicone can prevent the main cap from seating and cock it so the front half of the main bearing takes most of the hit and wear.

My rear main is leaking....66 389 tri power....i fear going thru this repair...knowing it may leak again....had same issue many yrs ago on a different 66. Im considering motor swap to something more reliable.

In regards to the above post, what do you mean by something more reliable and a engine swap?

Are you thinking about switch over to something other then a Pontiac just due to a rear main leak?

These days with the choices that Pontiacs have for seals if you can’t get one of these to not leak on you, then it’s not the seals fault, it’s a installation issue!

That post is spam.

Thankyou for that TIP...

Maybe I got lucky....but I installed a 1 pc BOP on my new eagle crank and I could NOT find anything I could/would do to make it fit any easier than it did. Only tip i can give is be gently when you twist it to get it on the crank..

why is there 2 of you now?

Im 100% with the 1 pc seal and 50/50 with the 2 pc seal.FWIW,Tom

https://www.youtube.com/watch?v=GQmfLtyMCFw

I wonder if the seal is put in backwards or maybe a core shift issue.

Good God how I don’t miss this. I had two ‘traditional’ Poncho builds in a pair of ‘73 Trans Ams for 8 years and 10 years each. Both very well built engines that made solid power and ran well. Both leaked out the rear main. One went back to the original builder who pulled the engine and replaced the rear main with a Graph-Tite. It rotated in the groove and leaked.

I ended up finding an old school, local mechanic who advertised as a transmission shop, but knew Buick / Pontiac / Olds like nobody’s business. He did 2 engine out rear main seal replacements with 1-piece Viton rear main seals. We also swapped fresh aftermarket oil pans from BOP along with 1-piece Viton pan gaskets. The 455 was literally bone-dry for as long as I owned it. The 400 stroker started weeping about a dime sized spot after a good hard drive. Wipe it up after parking, and no more would drip. We wondered it if wasn’t seeping through the deeper serrations in the aftermarket stroker crank - but he did wipe the serrations down with Emory cloth and mineral spirits before re-assembling.

Rear main seal leaks can be a nightmare. Gotta’ ask yourself how much is actually leaking - if it interferes with the pressure plate / clutch (on manual trans cars) - and how much it really robs you of your ability to just enjoy the car. If its a dime to a quarter sized drop after a day of enjoying the car, probably not worth an engine out rear main replacement.

There was a video on you-tube about how to fit the one peace rear seal.
Don't remember the name, would have to do a search for it.
It was pretty interesting though. Good luck..

GT

Rear main seal.
 

Going to give it a shot at 2 piece vitron... i have a classic car shop lined up....righy now i lose about 2/3 to 3/4 qt ever 2 tanks fuel.....bottom car is cover in oil🤦*♂️gotta luv the armchair qb who knows how to fix it from his swival seat

The "main" reason I have LS engine in one of my Pontiacs. I like Pontiacs as much as anyone else, and have owned or currently own more than the average person here. My first Pontiac was back in 1975, a 1972 GTO. It didn't leave any stains on the gravel at our family home, but there was oil seeping every where. A little gunk kept it clean. Then, in 1979 I moved up to a '77 GP SJ. Again, no driveway stains but seepage everywhere.

Since then during the '80s and '90s, I've acquired various Pontiacs that I have tried to seal PERSONALLY, and farmed out professionally. I drive mine regularly, and none have succeeded.

I feel the problem is that once these engines get machined away from factory spec, aftermarket sealing materials simply cant compensate, especially since their tolerances aren't spot-on with factory specs. Replacement cranks and such are simply going to have differences. Add in the fact that rubber composition isn't the same and who the hell knows?

Now I'm gonna get hammered for this, but here is my advice. If you only drive your vintage Pontiac to shows and less than three thousand miles a year, disregard. But if you like the styling of your vintage Pontiac, and desire to drive it on a REGULAR basis, consider putting that vintage Pontiac engine in hybernation, and let a more modern engine relieve you of those headaches. Then, if you decide to sell, reinstall the vintage engine.

You can literally take a 150k mile pull out complete LS engine for under 1k and have a more reliable. leak-free engine completely installed for much less than what the cost of a proper Pontiac rebuild, that is still prone to leaks and other problems, would cost. LS engines are easily converted to carbs so if you don't want the expense of fuel injection you can still have the same RELIABAL, leak-free power.

See, these Pontiac diehards here think that everybody has the deep pockets to keep paying the so-called pros big bucks to continue to chase seemingly simple issues. But they never go away and you keep spending and spending and spending. Sorry, folks, I've had enough.

Guess I learned something from your post. While my Pontiac engines seal up great and don't leak after a rebuild, my Yukon XL with an LS engine marks it's territory wherever it is parked.

So I can pull out one of these leaky LS engines and they magically will stop leaking when dropped in an old Pontiac?

You might also consider throwing out the baby with the bath water.

Or you can just put a piece of cardboard on the garage floor under your real Pontiac engine. Costs a lot less than $1k too.

First off, I would guess that your Yukon has more than 150k miles. You didn't state what year it is but I would bet that it's 2003 or older. And I will also bet that most rebuilt old pontiac engines (that are used regularly) leak more than any old LS.

Please, understand, my problem is NOT with Pontiac designed engines, or what they represented in it's heyday. My problem is with replacement parts that were designed (hit and miss as they are) for STOCK engines. Trying to make these questionable parts conform with AFTERMARKET parts is going to be a challenge.

My whole point is, If you want to show you vintage Pontiac and drive it occasionally, keep it stock. If you want to daily drive your vintage Pontiac and have a reliable drivetrain to motivate it, put your vintage drivetrain into hybernation and use a more modern LS. You can use carbureted or FE. Either way, it will give you far more enjoyment than constantly chasing problems that the industry has left behind. You can continue to chase high dollar parts to keep your car original, but will never again function the way they were designed.

I own my vintage cars to enjoy them, not to wait for sale to the next highest bidder.

I currently own four LS engine equipped vehicles. 1. 2004 GTO that I bought new in 2004. Currently has 100280 miles, not one single drip on my driveway, some aging gasket seepage noted, but no dirty driveway.

2. 2004 GMC Envoy SLT w/5.3 bought w/80k miles , currently with 120111 miles. No drips on my driveway.

3. 1972 Lemans that had the LS1 conversion back in 2008. No leaks but seepage due to aging gaskets. Engine has 89k miles,

4. 2006 GTO w/11200 miles, bought new. Not driven enough to make a comment. But currently no leaks on my garage floor.

My personal experience dates back well into the mid seventies when it comes to Pontiacs. And I have not been without a Pontiac since my first purchase in 1975 of a '72 GTO.

I don't know who builds your engines, but everyone I've tried from SC, to KS, MO. None of these engine builders have found success. And yes, they were all professional shops. Don't get me wrong. It's not the engines. It's the subpar aftermarket products. And after forty some years, I'm done.

If done the way the Pontiac shop manual shows, the graphite rope seals don't leak. I've done many Pontiac, olds, olds diesel, and buick rear main seals with very good success. Working in a dealership, you get to do it over the second time for free, if it leaks the first time. If you do a couple over for free, you make sure they don't leak the first time.

I've packed the agitator shaft on a storage tank with graphite rope seals that has thousands of gallons of fluid pushing on them with no leaks.

At this juncture of time any Pontiac engine that still has a factory seal in it in most likely rotted, and leaking, the rest have been replaced. Many times they were done with the rope that didn't have any asbestos in it. (OEM rope seals were made with asbestos, that was later prohibited). That non asbestos rope material just doesn't hold up, and leaks frequently.

The correct size graphite rope seals as well as the old asbestos rope seals did seal the cranks on Pontiacs, as well as the olds, and buicks..

I'm not buying the one piece LS, and SBC seals don't leak, I've replaced plenty of the one piece seals in GM engines. V8s six, and four cylinders with the one piece seals that leak frequently. Same goes for the 2 piece neoprene seals that chevy, AMC, and some fords used, I've replaced all of them.

I've never tried the rubber aftermarket seals in a Pontiac, but if you look at the serrated area of the crank on any GM OEM cranks that were intended to be used with a rope seal. I would never expect that raised toothed area not to ruin the sealing lips on any one, or two piece seal, it's like running a file over the sealing lip.

Putting an LS engine in a Pontiac because you couldn't stop a rear main oil leak is pretty laughable. FWIW, my 144,000 mile 05 GTO leaks oil, bought it new so I know no one has had their hands on the engine. My 71 455 that I rebuilt in 89, doesn't leak so I guess I should put a 455 in my 05 GTO.....:noidea:

Once you put a LS in a old PONTIAC it is no longer a PONTIAC.
Its about the engine more than anything else. A 69 Chevy, Olds, Buick and Pontiac were the same car, the difference was the engines.
Its all about the engine, the sound, the torque.
And not being like everyone else.
Pontiacs with LS engines in them are lame,lame and lame.
When I see those I turn and walk away. Weak.

Basically, if driven ... old cars leak, old engine designs leak. I don't want them leaving puddles, but "drops" are just the nature of the beast I think. I try to think back to when I was driving them as daily transportation .... how much of a leak would I have tolerated back then. Probably a lot more than I'd tolerate now.

I grew up having to park my cars on the street cause my Dad didn't want them leaking in the driveway next to his new cars.

I have the 2 piece viton (3.25") rigth now, considering getting the 1 piece version, as i am going to pull the motor soon.
Here in Norway we fail the bi-anual vihecle inspection if 1 drop of fluid hits the floor during the 1 hour inspection. We then get 2 months to fix the leak and come in for a post inspection.
If it still drips the vihecle fails and licence plates are taken, until we can fix the problem again.
Needless to say i am abit anxious about this as i am due in 2023 (the last inspection as the vihecle is then 50 years)