My leaky woes....rear main seal

[TT91]

Rear main seal problems, 300 miles on motor, been running synthetic for 150 of them. Switch back, replace the seal, what to do? 2 piece seal, A4 block.

This peice of cardboard was new. I took the stang out, made a few 10psi pulls, next few days it sat and accumulated this..

Oil is dripping down the bellhousing, tranny, and burning off my the X-pipe.

Overall, this sucks. Should I switch back to dino oil and ditch the synthetic, replace the rear seal?

 

[RsStanG1987]

Maybe something is jacked back there. I seen something today on TV about flat head motors having a rear main problem. They developed somesort of rear main seal that was made of teflon and kevlar or something. Maybe they make a better one for 302's

 

[DMAN302]

TT not sure if dino oil can put a stop to leak of that degree. I'm confused...is the block your currently using difficult to attain rear main seal? or is it more difficult to install? Looking at the amount of oil that's escaped I'm not sure if not replacing is even an option..the life of your clutch will be seriously affected as I'm sure your quite aware.

 

[bill302]

could crankcase pressure be causing seal to blow?

 

[86bluecobra]

you should inspect where the seal contact the crank make sure there isn't some sort of a burr that cause a premature seal failure.

 

[RacEoHolic330]

damn mike, I think your blow by issues you had earlier did a number on your seal. Definitely seems like excessive crankcase pressure to me. You might be forced to lay down the bills for a vacuum pump to help the situation

 

[HISSIN50]

Mike, my first thought was about the crankcase ventillation situation as well (esp since you mentioned the puddle increasing after the .7 bar runs).

Could that be an issue?

 

[TT91]

Mike, my first thought was about the crankcase ventillation situation as well (esp since you mentioned the puddle increaseing after the .7 bar runs).

Could that be an issue?

sure could, I had my valve covers sealed at the time.

 

[old_blue]

sure could, I had my valve covers sealed at the time.

WHOA!, I would definitely have to agree then. Did the same thing to a friends supercharged camaro. (chevy has terrible rear main seals regardless) Had the top buttoned up with sealed valve covers and the rear seal pretty much popped out. Was all brand new and we just thought it was a bad seal. Oil was all over the clutch and everything from the floor pan bottoms down had a nice coat of oil. We put on a new seal and, to be on the safe side, put on a set of tall valve covers with a breather and we had no more issuses..... besides it being a chevy. Good luck man. I would love to see some clips of this beast running.

 

[bdazzgt]

Mike, i always thought that you should run dino oil for the first 1000 miles. My comp cam card said to not run synthetic oil for the first 1000 because it wont allow the piston rings to seat against the cylinder walls and wont allow the cam to break in properly. Now i am not mechanic at all, and I know new cars come with synthetic, but maybe this was the problem by not letting the rear seal seat properly or somthing there i gave it a shot.

 

[302RollinHard]

I don't think that synthetic oils has anything to do with a rear main failure. It either was put in wrong in the first place, some kind of burr or deformation of the mating surfaces, or the big red flag...having the engine buttoned up so tight and running it so hard. I don't really buy they whole no synthetic till a thousand miles, either. But definitely not for a rear main failure.

 

[HISSIN50]

I hate to go off Topic with it, but everyone has a different view on how soon to hit the synthetic. When properly broken in, most of the initial ring-seal seating takes place in that first run.

In regard to the other comments, when a mill is built to run synthetic right off the bat (which he didnt), the machine work is slightly different to accomodate the extra lubricity.

I would inspect/replace parts at the rear of the motor, rig some sort of ample crankcase breathing (even if crude, for diagnostics. Later it can be cleaned up and made streetable) and see how it does.

My two cents.

Good luck Mike.

 

[TT91]

I would inspect/replace parts at the rear of the motor, rig some sort of ample crankcase breathing (even if crude, for diagnostics. Later it can be cleaned up and made streetable) and see how it does.
.

Besides what the naked eye can see, is there any way to establish that my rear seal needs replacing? When the flywheel came off, there was only a small drip, it seems to occur mostly when it gets hot. I pressure tested the intake track last week in search of vacume leaks, I used 20 psi from and air compressor. Would it be bad to hook it up to the bottom end and test for leaks out of the RMS?

 

[HISSIN50]

Besides what the naked eye can see, is there any way to establish that my rear seal needs replacing? When the flywheel came off, there was only a small drip, it seems to occur mostly when it gets hot. I pressure tested the intake track last week in search of vacume leaks, I used 20 psi from and air compressor. Would it be bad to hook it up to the bottom end and test for leaks out of the RMS?

Mike, that was a line of thinking I considered too. I just have not ever done it, so I am unsure of any undesirable side effects.
I dont see why one could not slowly add air into the crankcase, and note any hissing noises heard in the main seals. That seems kinda safe to me, but DON'T take this as something I have done. I am just brainstorming with you.
I dont see why that would not work, and I cant really think of anything it could hurt (you already had some decent pressure going on inside there anyhow).

I might replace the RMS if you have any doubts (if it was teflon, it might be ok anyhow). Otherwise, I worry about the seal's lip having been hurt if it deformed when pressures built up.

Let's see what others say.
Good luck Mike.

 

[Rick 91GT]

Mike I saw you mentioned a 2 pc rear seal, but if memory serves correctly you were set up for a 1 pc right?

If your using a 2pc seal I can talk you through the installation to help prevent leaks, you leave about 3/8" of the seal out on opposite ends so it doesn't leak at the parting lines of the caps, a little dab or RTV is also needed.

For a 1pc seal, clean the area very well, coat the crank with a little bit of oil, coat the outside of the seal with RTV and carefully tap it into place, clean off the excess, smooth it with your finger. Let it set-up over night, you should be fine.

If your running a vac pump they sell a double lipped seal to help seal it up tight, although the stock 1 pc seal seems to work just fine also.

Make sure the crank looks like a bearing journal, no marks, scratches, burrs, etc..

Make sure you Loctite or Teflon seal your flywheel bolts or oil will come out there also..

 

[vristang]

Mike, that was a line of thinking I considered too. I just have not ever done it, so I am unsure of any undesirable side effects..

Interesting idea guys.
This is not too dissimilar to performing a leakdown test on cylinder bores. A bad cylinder will dump compressed air into the crankcase. Pressurizing the crankcase should be fairly safe, unless too much pressure is used. How much pressure would be needed will depend on how much pressure is generated in your crankcase. Find this out by sticking a pressure gauge on the the valve cover vent or something similar.

That is all I can come up with

jason