390 Rear main seal

[wyngnut55]

Anyone ever replace a rear main seal in a 360/390 without pulling the engine? I know its a 2 piece seal, the oil pan has to come off and so does the rear main bearing cap. Can the old seal be fished out and new one installed fairly easily?

[cep62]

If it has a rope seal it's damn hard to do without dropping the crank.

An old mechanics trick is to pull the cap and take the old bottom rope seal cut a couple chunks and jamb it into the top part of the seal channel.
use a brass or aluminum punch so you don't hurt the crank.
The object is when you force the seal in it tightens the top half , then use a new bottom seal and hope for the best.

If you have a rubber seal you may be able to fish it out, and a new one in.

Now rumor has it ,If the bearings are badly worn the crank may be jumping slightly and a new seal may not work.
Maybe you can tell when you pull a cap or two.

[tnlprt]

The rear main seal on all FE engines is actually 6 pieces
upper and lower
2 side seals
2 nails

[Busboy]

It's very do able. It's not the funnest job, it's a pain in the butt. Double check the direction you're putting the seal in. When your upside down it's easy to get disoriented. Loosen the cap(s), drive the old seal out, clean everything, lube everything, slowly roll the new seal in. The side seals and nails will be more of a hassle than the seal itself.

[wyngnut55]

Thanks for all the info. Have to decide if I want to live with the leak, ( about 10 or 12 drops overnight after driving) Spend a day working under a truck on a creaper, or just say screw it and pull the engine and do it on a engine stand. Problem with pulling the engine, it could easily turn in to much more while the engine is out. Think some oil may be coming from back of the intake manifold and runnig down to the rear of the engine.

[basketcase0302]

"wyngnut55"Thanks for all the info. Have to decide if I want to live with the leak, ( about 10 or 12 drops overnight after driving) Spend a day working under a truck on a creaper, or just say screw it and pull the engine and do it on a engine stand. Problem with pulling the engine, it could easily turn in to much more while the engine is out. Think some oil may be coming from back of the intake manifold and runnig down to the rear of the engine.

The death of so...many FE's! Tried everything under the sun to avoid my rear main on my 71'.
I drove mine, (360) for some 3 years on 5 PSI of oil pressure (it would actually drop to 2 PSI the last year i drove it)!
But the FE will take it too!

[crazyhorse]

Mr Wyngnut, I was hoping someone would post a link to one of these rear main sear remover/installers that is more up to date than I am and there are probably more "up to date" tools for this now.
Maybe some one with a better method will post .

I used one on my 390 pickup some 20+ years ago (not exactly like this one shown in the link , but similar to it) .
I had no problem removing the old seal and installing the new seal with the little tool.
It made the job easy and simple.
I still have my removal/installer tool some where in my garage but could not locate it since it has been well over 20 + years ago.
One could be home made to work but the price is very reasonable.
I hope this will make your job easier.
Good Luck.

https://www.ebay.com/itm/P-Tool-Upper-R ... :rk:1:pf:0

[Busboy]

The only tool you need is a small screwdriver and some common sense.

[wyngnut55]

The death of so...many FE's! Tried everything under the sun to avoid my rear main on my 71'.
I drove mine, (360) for some 3 years on 5 PSI of oil pressure (it would actually drop to 2 PSI the last year i drove it)!
But the FE will take it too!

Wow you called it on the nose! When this truck gets nice and hot at idle, oil pressure is REALLY low! 2to5 psi range. Its not a every day driver so I can probably make it last. Will replacing the rear main seal bring the pressure back up?

[basketcase0302]

It should-but with any older engine with loose tolerances and worn bearings and rings it might be a band aid that might not help much either.
Always worth the effort though to avoid a rebuild, (especially if you can't afford to take the truck off the road long enough for a rebuild).

[wyngnut55]

I don't know the trucks history or how many times the odometer has turned over. It just turned over about a week ago. I have put about 2000 miles on it. When I bought it in Tucson AZ as a retiree project it didn't run, 98,200 miles on it. Kid had spark plug wires crossed. Got it running, seemed OK. Then tore it down to frame. Thought I would give engine a try before rebuilding it. It doesn't smoke or burn much oil I don't think. About 800 miles a quart. Think it might be leaking most of that while driving.
Don't need to use it much. Think I may live with it till I get motivated again, pull the engine and do a rebuild. Maybe add some performance parts.
Thanks for the info!
71 F100 Ranger XLT C6 390 long bed. Boxwood green