1 Piece Rear Main Change

[rcazwillis]

I need to change the 1 piece rear main seal. Engine is leaving a puddle when parked. Pretty sure it is not the pan gasket, too much oil.

Can the seal be changed without removing the pan? I see some online stuff where it appears others are doing it without removing the carrier.

Anyone have experience with it?

[B. W.]

Yes, you can change it without dropping the pan. Just pop the seal out of the carrier & install the new seal.

[rcazwillis]

Should I use a sealer of some sort? RTV would be a bad idea. Thinking I saw a recommendation to use a gasket sealer.

[kwmech]

No silicone needed. Fun part is getting it in without rolling the lip of the seal. Use a lithium grease around the lip of the seal and some in the V of it prior to installation. Do not remove the aluminum piece from the block. And be careful getting the old one out as not to damage the aluminum

[rcazwillis]

The new seal has a plastic sleeve inside. Looks like it is there to help get it over the crank.

Should have done this when it was on the stand...

[Bigdav160]

I've never seen one leak that bad. Sure it isn't coming from above?

[rcazwillis]

I figured it was sending unit area, but there is zero oil on top of the block or transmission. Nothing around the valve covers. Completely dry. The drips come from the back of the crankshaft between the flex plate and pan. Oil is being slung inside the bell housing and on the starter. No dust cover on it. Has to be seal or pan gasket. I did replace the pan gasket, so it could be there. After it idles, it will start dripping immediately. Crank seal, right?

[kwmech]

Cam plug?

[rcazwillis]

Originally Posted by kwmech

Cam plug?

I will check. Don't think so, but have not looked at it.

[AussieinNC]

Did you use the one piece pan gasket that's available?

[rcazwillis]

Originally Posted by AussieinNC

Did you use the one piece pan gasket that's available?

Yes it's the one piece gasket

[rcazwillis]

I think it is the pan gasket. The area above the gasket is dry.
Since I did it wrong...what tips do you have for successfully installing a one piece pan gasket? Felpro?

[Rickysnickers]

If you are using the blue one, the instructions say to put it in dry. I have had to replace the oil pa gasket 2x. the first time I did it per the instructions, dry. It leaked. The second time, i used RTV on it and it hasn't leaked. With that said, I am referring to the front of the oil pan where it meets the timing cover. That's my tip, FWIW.

[rcazwillis]

I used rtv on both ends. I was thinking this was causing the problem. I can see where it squeezed out around the block/rear main carrier. Looks the same in front, but not leaking there.
Thanks for the tip.

[kwmech]

Oil pan leak will not usually gush out and fling around like you describe. And if on the stand, it was likely that the gasket was put on correctly. Just a thought

[jocko]

Only tip i can share is to not overtighten the pan bolts, observe the torque specs and tighen em in a crossing latter as if it were cylinder head bolts... It sounds simple and you probably didn’t do that, but I know i have. If it squished out as you mention, that might be your only issue.

[rcazwillis]

Zane pulled the pan off last night. I installed the new pan gasket. Still leaking. Must be the rear main. Doing that tomorrow.

[AussieinNC]

When you pulled the pan to replace the gasket, did you pound down the dimpled pan rail around each bolt hole?

Way too many times I have witnessed builders forget such a simple step, that will always lead to leaks....

Where the bolt passes through the thin metal lip of the pan, the pan flance will dimple up like a small mushroom (see pic)...

If the tech doesn't flatten out the old pan rail, the mushroom cuts the new gasket or the pan bottoms out against the engine block without the proper crush on the gasket.

Same goes for rocker cover rails, timing cover rails and auto transmission pan rails, rear end covers, anywhere a tin flange meets a gasket.

There are some one piece pan gaskets that have embedded small metal collars around each bolt hole to assist with this issue. I always use RTV on these one piece gaskets, plus perform the pound down process.

There is also the possibility that the rear seal is leaking,,,,make sure when you pull the seal to check for a groove in the crank seal surface itself....

Finally, check the PCV system is not clogged up, preventing correct air movement inside the engine...if it clogs, the engine will build up pressure inside the crankcase and will push out gaskets, seals, whatever ....

Hope the above helps...

[rcazwillis]

Rails are flat. Checked before I installed the first time and again today. The leak is very much around the rear of the block.

I have not checked pcv. Good idea. You would think it would leak around the valve covers too, but they are dry.

I am back to the rear main leaking.

[painterljp]

If it's a 1 piece rear main it is a newer engine. My sons 88 blazer has a 1 piece rear main. It also has 2 oil sending units. One behind distributor with a 90 elbow on it. It is for a idiot light on dash. Has another for gauge oil pressure down by the oil filter. Check both of those and make sure they are both there. If not would be shooting oil out. Everyone says there shouldn't be 2 sending units but there is. It is a stock engine we just got done putting it back in truck.

[weq92f]

Here's what I did to install one piece gasket with the engine installed in the vehicle, although sounds like that is not the source of your leak...

http://67-72chevytrucks.com/vboard/s...0&postcount=32

-klb

[AussieinNC]

I have also seen the rear cam plug partially walk out of its bore and leak oil....only real way to find out is either yank engine or pull trans....

[rcazwillis]

I think we have resolved the leak. Today we pull the trans and flex plate. The corner of the pan gasket was not sealing to the block. Ended up pulling the pan, again. What I found was sad. The studs for the pan gasket that are part of the rear main seal had what appeared to be a shoulder that was preventing the gasket from sealing. The shoulder ended up being remains from an old gasket. The sleeve embedded in the one piece gaskets must have pulled out of the gasket when removed. It was still on both studs. Pulled the seal carrier, put a new seal in it, pried the seal sleeves off the studs and put it all back together. The pan gasket now seals up against the block. SHOCKING.

Sometimes, I can't get out of my own way.

[kev2809]

lol it happens....

did the same thing on my dump truck when i first got it. dropped the pan to change the gasket. when i rebuilt the motor my mechanic who did the work was dropping the pan...said " look at what the dumbass did who changed the gasket...they left the old one on and put a new one over it!".

i laughed and played along..lmao...

i never even seen that gasket on there