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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
So I recently spent several days of my life removing the auto trans in my IROC vert so i could address what i believed to be a rear mail seal leak. The whole underside of the car was a mess so i could not be sure. I cleaned everything up and replaced the seal. Didn't look too hard. Put it all back together... leaks as bad.. maybe worse!...
Before i did this i looked around for tips or videos about how to do the one piece and i couldnt find anything. Having done the 2 piece rear mains on my 69 and 85, i eventually figured out the trick to getting those right... after doing them a few times. Given how much work it takes, i am NOT looking forward to doing this again... Given the size of the leak, i really cant drive it until its right.
It shows all the signs of a rear main leak. Oil on the starter and trans cooler lines, dripping from the converter dust cover. It is definitely NOT coming from the top of the engine. Had cleaned those spots and they are still good... If there is one nice thing.. its that a clean engine makes this easier to see.
See the mess i had after running the engine, maybe 15 minutes,,,
I installed the Felpro seal as instructed.. dry.. but the flimsy installation sleeve broke as i was trying to push it on. so i installed it by hand.. carefully seating it slowly going around the perimeter. it looked real good once installed... not crooked, but flush and smooth...
The oil pattern on the inside of dust cover really looks like a rear main leak to me....
So who can give me better tips on how to install the seal, clearly something went wrong on this install. And its not that the seal did not go in square... I need to know what to do right before i tear this thing apart AGAIN...
You need a tool to push the seal into place. A PVC pipe cap the same OD as the seal usually works well, the goal is to push it in evenly without causing the garter ring spring inside the seal from popping out of it's groove. If you tap one side, then the other, you'll probably have problems. If you hammer it in, you'll probably have problems.
I suppose you checked for leaks at the oil sending unit, the oil galley plugs, the camshaft freeze plug, the rear seal of the intake, the distributor gasket, etc? The 1pc rear main seals usually don't leak, they're generally a quality rubber and they're 1 pc. They like to seep, a drip or two now and again. All of the other things will leak much heavier.
The rear main seal housing also must be properly centered on the crank. Ask me how I know.....
Check with some calipers. Needs to be centered within about 0.005"
No real trick to installing. Be carful with it. I prefer the Viton seals to the PTFE ones. I just replaced mine today due to the aforementioned housing alignment issue. Tapped it in carefully and seated it with a hammer and a short 3/8 socket extension working my way carefully around it. After correcting the housing alignment of course.
I never removed the seal housing and it does not appear to ever have been removed....not sure that is the issue.
- Just replaced the oil sending unit, dry around it
- rear of intake is fine... wouldnt that leak go AROUND the bellhousing anyway?
- just replaced the distributor, new gasket... dry there.. same question as intake...
- I will have to double check the oil galley plugs and freeze plug
I also tapped around the perimeter to seat it using a socket...it looked really good in place. Did the inner lip rollover? ..not sure.
Again... look at the oil dripping from the flywheel.. look at the oil pattern on dust cover... doesnt look like it coming down from above.
Whenever i get back to this.. so frustrated i moved the car to storage.... i need some time....
I am planning to try Viton next time... this one was PTFE
What ever is leaking seems to be under pressure... and gets worse when i rev the engine and increase the oil pressure.
Don't use the PTFE seals on an older motor or one that has had a PTFE seal on it in the past. The PTFE seals are very rigid and they usually cut a groove into the crank. They also deposit PFTE on the surface (this is why you install them dry)..... they need a laboratory clean, perfectly machined surface to seat well and are not recommended for use with speedi-sleeves, etc. I would install a crank repair sleeve, and a Viton seal and you'll likely be back in business.
I like lubriplate (assembly lube) for coating the lip on the viton seals.
If you walked it in, tapping around, you probably done messed up, A-A-Ron. Look at the special tool in the book. Ideally you want to push the seal in with constant pressure around the entire seal.
Funny, looking around I can't even find photos or video of anyone doing it right online, yet every GM or Ford service manual I've ever seen shows installing 1pc rms with a constant pressure driving tool.
The special tool for the SBC is a J-35621, you can Google that number to find a photo. Or search for "rear main seal install tool" and see how other people have fabricated a tool to do the same job.
I figured if there arent endless videos or tutorials online... it must be pretty easy....hard to screw up..... guess i was wrong in that assumption... something must not have gone right...
OK...now someone put out a nice video with all this basic info and i will copy that to a tee....
If i have to do it a third time, there will probably be a minor nuclear explosion in my garage...
That seems like a pretty big leak for a rear main. Maybe a 35 year old rotted away rear main with gaping holes, but not a new rear main installed at a slight angle or something, especially a one piece seal. You mentioned it acts like a pressure leak. I would spend a little more time probing the back side of that engine and any pressurized oil ports. I have had more than one engine spring a leak like this from oil pressure fittings and sensors. The last two I had were very hard to find due to lack of space to see anything at the back of the engine.
I figured if there arent endless videos or tutorials online... it must be pretty easy....hard to screw up..... guess i was wrong in that assumption... something must not have gone right...
OK...now someone put out a nice video with all this basic info and i will copy that to a tee....
If i have to do it a third time, there will probably be a minor nuclear explosion in my garage...
I don't have anything to add here except that I respect your tenacity , I've seen lots of people give up on a car for way less trouble , and here's to hoping you get it on the second try
I would spend a little more time probing the back side of that engine and any pressurized oil ports. I have had more than one engine spring a leak like this from oil pressure fittings and sensors. The last two I had were very hard to find due to lack of space to see anything at the back of the engine.
Which ones are INSIDE the bellhousing...? I already replaced the oil pressure sensor and that fitting (outside the bellhousing).
The oil galleries at the back are plugged where they are gun-drilled through the block casting.
And there's the rear cam journal plug also.
GD
Wow , I get to use this stolen pic twice in one week , schwing !!!!
Aaron , Drew , and the General are talking about the three small plugs and the big "freeze plug" looking thing seen straight above the crankshaft in this picture .
See , I knew if I hung around long enough I'd have something useful to add ....
Last edited by OrangeBird; 04-27-2020 at 03:06 PM.
Aaron and the General are talking about the three small plugs and the big "freeze plug" looking thing seen straight above the crankshaft in this picture
Ahem... I mentioned them in the first reply to the thread. Stop trying to steal my thunder.
Originally Posted by Drew
I suppose you checked for leaks at the oil sending unit, the oil galley plugs, the camshaft freeze plug, the rear seal of the intake, the distributor gasket, etc?
Like I mentioned earlier, the rear main seal usually won't leak that bad on a 1pc rms block, even if the seal is installed less than perfect or with high mileage. If it's really the seal leaking, it's probably because it was installed poorly. But I'd make damn sure it's not leaking from somewhere else before replacing the seal again. It can be hard to see where leaks originate as opposed to where gravity eventually separates the fluid from the lowest part of the assembly.
Ahem... I mentioned them in the first reply to the thread. Stop trying to steal my thunder.
Like I mentioned earlier, the rear main seal usually won't leak that bad on a 1pc rms block, even if the seal is installed less than perfect or with high mileage. If it's really the seal leaking, it's probably because it was installed poorly. But I'd make damn sure it's not leaking from somewhere else before replacing the seal again. It can be hard to see where leaks originate as opposed to where gravity eventually separates the fluid from the lowest part of the assembly.
Oops , sorry I missed ya , and since I'm always one to give credit where credit is due , I fixed the omission of you in my post
With the housing misalignment on my recent 350 build, it was a slow drip. My housing was mis-aligned by about 0.015". I got it back to about 0.003", put in a new Viton seal, and no problems. I tapped it in with a hammer and socket extension. You do have to be careful but I've done it by that method for many years without any issues. When this one leaked I was immediately suspect that some other factor was at play which was why I started checking the housing alignment. Took me about 4 hours on Sunday to drop out the trans, re-align the housing, install the new seal, and back together for a test drive. So far no problems and I was in a hurry so I used a Duralast Viton seal - at least it was made in Taiwan, not China. Seemed to be fine quality upon inspection.
I agree that seems like a LOT for a RMS. Perhaps if the lip was rolled though.
I'm sure GM has a positioning tool for the seal holder. I know Ford has a 'Rotunda' tool set for the 2.3L that includes just such a tool for the crank snout seal in front. I didn't want to spring for a tool I'd use once, so I installed the seal in the front cover first, and slowly tightened the bolts to allow the seal to center the cover on the crankshaft. Not my original idea, but it worked out great. That engine doesn't leak a drop. Same engine has a fancy one piece rear main, just like a chevy. I used a 4" to install the rear main, and it also doesn't leak.
Well... since that stolen pic is MY engine before the seal was replaced....from the transmission replacement thread.... it doesn't look like that stuff up there is leaking in the pic does it?
I just think it has to be the seal... especially since it seems WORSE after i replaced it....Occam's razor.....
I cleaned everything with engine degreaser before i reassembled... because i like a clean engine... and it was a mess.... far and away.. the biggest mess was inside the bell housing..
I'm sure GM has a positioning tool for the seal holder. I know Ford has a 'Rotunda' tool set for the 2.3L that includes just such a tool for the crank snout seal in front. I didn't want to spring for a tool I'd use once, so I installed the seal in the front cover first, and slowly tightened the bolts to allow the seal to center the cover on the crankshaft. Not my original idea, but it worked out great. That engine doesn't leak a drop. Same engine has a fancy one piece rear main, just like a chevy. I used a 4" to install the rear main, and it also doesn't leak.
Yeah - I did the same and tried to have the seal center itself while tightening the housing on the engine stand before the pan went on. I believe there should be dowel pins that locate the rear housing but mine were MIA. I figured as you did that the seal would center and slowly tightening in a star pattern would be sufficient. Seems not the case on my build. When I measured it with calipers with the seal removed the housing gap was 0.025" wider on one side than the other
Luckily I was able to loosen ALL the pan bolts, remove all but two of the housing bolts, and knock it around with a few taps and a punch till I had it where it needed to be then walked the bolts down and rechecked. So far so good.
You do realize of course, that you can clean up the mess on the block, put the starter and flex plate back on, run the motor for a bit, and get up under there and SEE where it's ACTUALLY coming from...
Looking at that nice dry block all around the bell housing flange, doesn't look to me like a RMS leak. Or at least, didn't used to be.
The special tool for the SBC is a J-35621, you can Google that number to find a photo. Or search for "rear main seal install tool" and see how other people have fabricated a tool to do the same job.
Originally Posted by erik69&85
I figured if there arent endless videos or tutorials online... it must be pretty easy....hard to screw up..... guess i was wrong in that assumption... something must not have gone right...
Yes. Damn, I don't exactly need to change a mainseal, but that tool makes me desire the tool. Of course that would lead to the desire to use the tool. Next thing you know you're in the parking lot at the mall changing mainseals on random parked cars. Something similar happened with the Ferrrd TFI tool, and the steering wheel puller, and the GM door hinge spring compressor.
Yes. Damn, I don't exactly need to change a mainseal, but that tool makes me desire the tool. Of course that would lead to the desire to use the tool. Next thing you know you're in the parking lot at the mall changing mainseals on random parked cars. Something similar happened with the Ferrrd TFI tool, and the steering wheel puller, and the GM door hinge spring compressor.
You drive up to Detroit, I'll buy you the tool, and you can use it on the T/A for me.
I did some digging, the tool runs close to $200. There was a used one sold on ebay for $75 back in February, I might just have to watchlist it and wait for one to pop up. Fortunately, near as I can tell, the 1pc rms lasts so long that if it needs to be changed, it's probably easier and due for a new engine.
I noticed in the video that they have sealer around the OUTSIDE of the seal as they push it on.... I did not put anything there.... anyone else do this?
I noticed in the video that they have sealer around the OUTSIDE of the seal as they push it on.... I did not put anything there.... anyone else do this?
Not necessary. But if you're really concerned about the seal moving can use the loctite blue gluestick on the OD. But that will REALLY screw the next guy for getting it back out.
Sealant/loctite on the OD can be useful if the housing is gouged or you have crankcase pressure that blows out seals.
I noticed in the video that they have sealer around the OUTSIDE of the seal as they push it on.... I did not put anything there.... anyone else do this?
When I did the RMS on my 4.3L V6, I did not put sealer on the OD of the seal. No issues.
Definitely stop guessing on where it's coming from. Or at least confirm your suspicions. Run it and put the eyeball on it or get some of this:
Run down to ACE Hardware and buy a 75W black light bulb, put it in your drop light and look for the glow (works best at night with the lights off).
I did some digging, the tool runs close to $200. There was a used one sold on ebay for $75 back in February, I might just have to watchlist it and wait for one to pop up. Fortunately, near as I can tell, the 1pc rms lasts so long that if it needs to be changed, it's probably easier and due for a new engine.
As low as $150 on eBay...but yeah, they're pretty proud of it. In fact, Kent Moore / OTC is pretty damn proud of EVERY special tool they make.
I think I'll stick to a 4" pipe cap, a steel strap, and a couple bolts and nuts, but man that tool makes it look like fun. Just not $150 worth of fun. That'd go awayz at the strip club if a guy were frugal.
I think I'll stick to a 4" pipe cap, a steel strap, and a couple bolts and nuts, but man that tool makes it look like fun. Just not $150 worth of fun. That'd go awayz at the strip club if a guy were frugal.
Here in Portland, we now have drive-through strip clubs (so the evening news says). Think maybe I'll spring for the RMS tool and pop down there to see if I could do some bartering. Best of both worlds. I'm betting with the Kung Flu going around some of those nice ladies might be in need of some "repairs".
Ok... update.. after taking a couple weeks off to settle my frustrations, I was back at it with a new seal. Dropped the trans, changed the seal, and put it back together in 4.5 hours... not too bad now that i know what i am doing.
Some notes:
- It is definitely NOT the freeze plugs or oil galley plugs. Bone dry in those areas. Have pictures.
- It is not the oil pan gasket, i put a lot of ultra black RTV on this area and it was still good... but visible oil dripping from the rear main.
- Getting pretty good with 3 feet of socket extensions... works really well. Almost easier that the second bolt on each side.
- 4 inch PVC caps are too big for the seal. 4 inch pipe is just right. I used 3 inches of pipe glued to a cap to give a good even surface to tap on. made it flat and true
- Cleaned up the sealing surface on the crank with emery cloth... saw this as a recommendation to give the seal a fresh clean surface.
- Just a slight lip on crank sealing surface from past wear... just enough to catch a nail
- Bought a viton seal this time.. National brand from RockAuto
I noticed something about the seal i removed...(the first replacement)... it does not look as good a seal as the new replacement... look at the back of the seal Front side... original on left, first replacement in middle, Viton replacement on right above... Picture flipped below...
The Viton replacement on left above looks just like the one that was in there originally (far right above). Much better back lip. Both have the radial spring on the inner lip.
The first replacement i bought from RockAuto (cheaper) was branded as FelPro and does not have the radial spring and the inner seal is flimsy at best.. see that deformation? Thats just from my fingers pushing on it. You don't get that with the other two. It stays tight and round.... It also doesn't have those oil control grooves... This was cheaper but it doesn't seem like it would ever work in this application.
No, i did not start the car to see if the repair work... i was feeling too good and didn't to ruin the moment... but its coming.
The middle seal is a PTFE seal. They don't have garter springs. They need to be installed dry with a VERY clean and VERY flat seal surface on the crank. When they startup they deposit PTFE (teflon) on the crank surface so that the "seal" is effectively teflon/teflon and theoretically should last forever...... in practice though they end up eating into the crank due to the lip being stiff and contamination of varnish, carbon, etc from the engine oil.
Started the car tonight....so nervous I was shaking....Success!!!.car ran for about 15 min without a drop of leakage.
I ran it still up on ramps, without the torque converter cover.... afterwards I crawled under to take a look...no drips...put the cover back on and got the car down....
I have only had success with viton seals on all my cars...and always clean the surface with Emery...
Now I can finally put the car on the road... For the first time it doesnt leak puddles of oil all over the place ...new front and rear seals...
Why do I always have to do rear main seal more than once?...but now I know the tricks for both one piece and two piece seals.... Prep is so important..and cleanliness.
Seal retainer was not an issue...the design of that epdm seal sucks... Use a seal that matches the one you already have... It makes a difference.
I literally cannot sleep until I solve these problems....
There is so little out there on how to install one piece seals... Lots on two piece seal. The first YouTube video was just added in April.... Had to really dig for info and tips... It's more than just pry out and pound a new one in...
04-26-2020, 02:21 PM
Wow , I get to use this stolen pic twice in one week , schwing !!!! 
See , I knew if I hung around long enough I'd have something useful to add ....
Oops , sorry I missed ya , and since I'm always one to give credit where credit is due , I fixed the omission of you in my post 
