rear main seal
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Freshman User
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rear main seal
Quick question, on my 78 f150, 4x4, it's leaking oil, decent amount, none is on the oil pan, but pretty much everything behind it is fairly covered. Is it safe to say it's the rear main seal? And if so, do I understand correctly that it's as easy as drain oil, remove oil pan, remove lower bearings, remove old seal, replace with new seal, torque lower bearings back down, and put it all back together?
Elder User
Joined: Apr 2011
Posts: 632
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From: Bremerton, Wa
Quick question, on my 78 f150, 4x4, it's leaking oil, decent amount, none is on the oil pan, but pretty much everything behind it is fairly covered. Is it safe to say it's the rear main seal? And if so, do I understand correctly that it's as easy as drain oil, remove oil pan, remove lower bearings, remove old seal, replace with new seal, torque lower bearings back down, and put it all back together?
but I thought you had to remove the flywheel/flexplate (which includes removing the transmission and bellhousing)
I'm curious about any suggestions from someone with more direct experience
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Freshman User
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From everything I've read on here, as long as it's a two peice seal, you can snake it around there. But after getting the pan off for the first time and seeing in there, oh boy, it's going to be really tough to do.
Mountain Pass
Joined: Jun 2004
Posts: 241
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From: Canada
A one piece seal comes out the back, two piece from the bottom. 302's changed from 2 to 1 in the 80's. Assuming it's a 2 piece, don't remove all the caps, only #5. Loosen the other caps to allow the crank to drop, but still support it.
One half of the seal is in the cap. If it was a rope seal, there will be a pin in the cap. this has to be removed if a neoprene seal is used. Usually if you rotate the crank while pushing on the end of the seal with a small screw driver, you can feed the seal out.
Replace the same way. Dip the seal in oil to allow it to slip in the groove. Make sure you reinstall in the proper direction. When you a feeding the seal back in don't shave any rubber off, it will leak for sure. Overlap the seal ends with the block surface and use a small amount of RTV on the cap edge. Rest is put back together same way you took apart.
One half of the seal is in the cap. If it was a rope seal, there will be a pin in the cap. this has to be removed if a neoprene seal is used. Usually if you rotate the crank while pushing on the end of the seal with a small screw driver, you can feed the seal out.
Replace the same way. Dip the seal in oil to allow it to slip in the groove. Make sure you reinstall in the proper direction. When you a feeding the seal back in don't shave any rubber off, it will leak for sure. Overlap the seal ends with the block surface and use a small amount of RTV on the cap edge. Rest is put back together same way you took apart.
Tuned
Joined: Sep 2010
Posts: 279
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If you follow the instructions above you will have the best results, at the Ford dealer we used to put a dot of silicone, (the size of a large grain of pepper) on the ends of the seal where they butt together, but we were doing them fast in and out, so if a small amount got on the crank we had it running before it set up.
We had several of those a week back when the 460/7.5 was under warranty.
We had several of those a week back when the 460/7.5 was under warranty.
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Seems easy enough. When I put the new oil pan gasket on, do I put a bead of silicone all the way around it on both the pan side and the block side? What kind of silicone do you guys recommend? Torque specs of the caps are 95-105, is that correct? Last question, I got the pan off yesterday, now it's raining today, so I may not be able to work on it today, it's not going to hurt anything having the pan off for a few days will it?
Cargo Master
Joined: Oct 2010
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Nope. Shouldn't hurt as long as you keep it dry under your truck. That stuff is soaked in oil. It shouldnt rust in two days.
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big problem here. I can not get the top part of the seal out. I've got all the cam bolts loose, but I can't get it to drop down. I got a feeling that once I do get it to drop down, there's no way I'll be able to get it out of there. The bottom part was damn near molded into one peice with the cap and was solid as a rock once it did come out. What do you guys think? Should I be able to do this?
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Ok, maybe I'm just panicking here. Just feel way in over my head. I think if maybe I can figure out how to drop the crank, I can fight the upper part of the seal out of there. My question is though, how do I get the crank to drop down. I've got all the caps loosend enough that it should just drop right down, except for the middle one. I've got it loosend, but the cap itself won't drop down, just wiggle back and forth slightly. The thought of throwing in the towell and taking it to a real mechanic is ever present, but at the same time, I'm soo close, just need to get that upper seal out.
Fleet Mechanic
Joined: Jan 2010
Posts: 1,287
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From: San Carlos, CA
I never had to do the rear main seal like this before. Mine is going out too so I will follow this thread.
To drop the crank so you can get the upper seal out I would try removing the spark plugs as the pistons and connecting rods are holding the crankshaft in place. (Besides the main Bering s) Then I would try turning the engine by the vibration damper bolts to see if that will loosen up the crank.
I'm not sure what is after the number 5 Bering that would need to be removed (or loosened) Chime in anybody?
To drop the crank so you can get the upper seal out I would try removing the spark plugs as the pistons and connecting rods are holding the crankshaft in place. (Besides the main Bering s) Then I would try turning the engine by the vibration damper bolts to see if that will loosen up the crank.
I'm not sure what is after the number 5 Bering that would need to be removed (or loosened) Chime in anybody?
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I was gonna try and hand crank it, but I don't have the right size socket. I read you can remove the plugs and then should be able to turn by tuggin on the belt, is this true? This is gonna turn into a couple weekends projects. It won't hurt anything having the pan off with everything exposed will it?
Fleet Mechanic
Joined: Jan 2010
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From: San Carlos, CA
It should be pretty easy to turn. The socket just gives you a little more control so your free hand can tug on the crank.
You should be fine with the exposed bottom end but if you have any concerns you can just put the oil pan on and hand tighten a few bolts just to cover it.
It took me 3 weeks to do my heads and I just covered the block and valley with paper towels. No troubles!
You should be fine with the exposed bottom end but if you have any concerns you can just put the oil pan on and hand tighten a few bolts just to cover it.
It took me 3 weeks to do my heads and I just covered the block and valley with paper towels. No troubles!
Senior User
Joined: Jul 2005
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The crank is not just going to just drop down it will hang up because the pistons are still connected to it just pull down on it or if you have a handy peice of hardwood use it to pry down on the crank be carefull to not get any dirt in there once it drops down the old seal may be sorta baked in there(it hardened over the years which is why it is leaking). My Dad would use a piece of heavy gauge steel wire to force the old one out and it does work good (amazing how them old guys knew all the neat tricks).