HELP! New Motor rear main seal Leaks

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blewbyoutobad

blewbyoutobad

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I have a standard 340 that the machine shop rebuilt the short block 4-5 years ago. Fired it up after it sat for about 2 years. Finally getting to drive the car and the rear mail seal leaks. Any thoughts or ideas. I really don't want to pull the engine.
Thanks FABO

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Depending on how bad it is you could just leave it, otherwise you need to drop the oil pan and maybe some steering linkage to replace the seal. But it CAN be done with the engine in the car, did it myself once.

My guess is they only pre-lubed the seal with motor oil and after sitting 2 years it got dry and burned up when you started it the first time. Or they put it in wrong which isn't uncommon, I find it works better actually to NOT stagger the two seal halves (one end sticking out slightly) especially if the seals have the locating tabs on the sides.
 
blewbyoutobad said:
I have a standard 340 that the machine shop rebuilt the short block 4-5 years ago. Fired it up after it sat for about 2 years. Finally getting to drive the car and the rear mail seal leaks. Any thoughts or ideas. I really don't want to pull the engine.
Thanks FABO

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Well, if you MUST park your car in the living room on your wife's white carpet, I would recommend a drip pan.

:realcrazy:
 
Ottmundr said:
Well, if you MUST park your car in the living room on your wife's white carpet, I would recommend a drip pan.

:realcrazy:
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:rofl:LMAO looks like a concrete garage floor to me. Oil stains on carpet don't spread out like that, don't ask me how I know
 
MOPEkidD-3 said:
:rofl:LMAO looks like a concrete garage floor to me. Oil stains on carpet don't spread out like that, don't ask me how I know
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It is hard to see with my eyes which are getting a little bit creaky here. Heh heh

The damed HOA here bitches at me about my rear mainseal leak, so instead of putting a new one in with the engine still in the car, I just bought a 1991 360 to rebuild in the back shed.

Why spend $14 for a seal on a tired old 318 when I can instead build myself a new 360 for thousands more? (With some six and half year old help?)
 
Ottmundr said:
It is hard to see with my eyes which are getting a little bit creaky here. Heh heh

The damed HOA here bitches at me about my rear mainseal leak, so instead of putting a new one in with the engine still in the car, I just bought a 1991 360 to rebuild in the back shed.

Why spend $14 for a seal on a tired old 318 when I can instead build myself a new 360 for thousands more? (With some six and half year old help?)
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Oh God don't get me started, I HAAATE HOA's!! Our neighborhood doesn't allow non-running vehicles to be parked outside even if it's in your own driveway. I'm living in my parents' house though so it wasn't my choice to live in an HOA community lol. I made a promise to myself the first house I buy will be with no HOA on a big lot where I can park all manner of old vehicles, running or otherwise. I'll give up being close to everything if it means I can make my property look however the hell I want.
 
Before you going tearing lower end apart, make sure it's not the oil sender, valve cover or even possible intake manifold leak. I thought I had a main seal leak and found out it was oil sender and a big sigh of relief.
 
If it were me, I would look at a way to fabricate a small discrete "diaper" that you could attach to the pan rail bolts, the trans inspection plate bolts, some thin flatstock, with some new super absorbant material attached to a small backing plate that would be easily changed.....no talcum powder or ointments required. Seriously, something like the above vs. tearing things apart. I'm all over the fab work.
 
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Builder may have put one half of the rear main in backwards. Not that hard to do, I've been guilty of that.
 
I pack every lip seal with grease before installing. It holds up longer during first start up until the engine oil can reach it. That’s how we do it in aerospace. Never know how long that part will sit around before going into service.
 
If you don't want to rear it back down to fix it, just throw it away.
 
Like tonysrt noted, check easy stuff 1st. If it is the rear main, it's not difficult to do in the car. Recently did in on mt Duster. Dropped the steering linkage and pan. Eazy Peazy. I lucked out in that I was able to drop my pan without removing my old hooker comp headers.

Good luck!
Pat
 
Thanks all, some really great tips and advise. I've had the oil pan off once to fix a leak, that was my doing when putting the engine together. Not that hard. I have AlterKtion so no torsion bars. I am anal about oil leaks so I guess I'll be tearing it down. Does the upper seal come out easily with the crank bolted up but the main cap off?
I really appreciate all the feedback. I live in an HOA and they don't like me at all. Maybe if I drove a Cheby.
 
I might be wrong but I think the rear main bearing cap mating surfaces should get a thin coat of RTV as well.
 
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RedFish said:
I might be wrong but I think the rear main bearing cap mating surfaces should get a thin coat of RTV as well.
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Then we are both wrong, because I do this with every main cap every time and so far never have had a leak after doing one.
Just a light strip of a thin film all the way across from the seal edge across the cap and up the little corner to the pan gasket.
 
blewbyoutobad said:
Does the upper seal come out easily with the crank bolted up but the main cap off?
I really appreciate all the feedback. I live in an HOA and they don't like me at all. Maybe if I drove a Cheby.
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You can carefully tap the top seal out/around enough to pull it out. Mine was in there a loooong time and took a bit of tapping to get it out. No need to loosen the cap.

Pat
 
I can't find the picture but I made a tool push that seal out and push the new one in. I cut the head off of a toothbrush and made a plastic push tool. That way it was strong enough to push the seal but not harsh enough to scratch any metal
 
I'm as anal as they come about oil leaks and I always use the black Right Stuff. Four years with my Stroker and mostly drag strip and knock on wood no leaks.
Permatex_Right_Stuff_Replica_01.jpg
 
j par said:
I can't find the picture but I made a tool push that seal out and push the new one in. I cut the head off of a toothbrush and made a plastic push tool. That way it was strong enough to push the seal but not harsh enough to scratch any metal
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Blewbyout - j par raises a good point, definitely use a "soft" material to push/tap it out.
 
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Since this is a 4 speed car and I am running a blow proof Lakewood bellhousing, if the leak was an oil
galley plug on the rear of the block wouldn't the oil be dripping off the outside of the shield that bolts to the back of the block? Just thinking if it could be something else.
 
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Common occurrence is people setting the motor down on a tire, or even on the flat of the oil pan. The rear seal compresses...after time sitting...once lifted and in the car, there is no longer 300 lbs of clamping force and the seal already hardened while sitting compressed...leak time.
 
MOPEkidD-3 said:
Oh God don't get me started, I HAAATE HOA's!! Our neighborhood doesn't allow non-running vehicles to be parked outside even if it's in your own driveway. I'm living in my parents' house though so it wasn't my choice to live in an HOA community lol. I made a promise to myself the first house I buy will be with no HOA on a big lot where I can park all manner of old vehicles, running or otherwise. I'll give up being close to everything if it means I can make my property look however the hell I want.
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DO NOT BUY A HOME IN A TOWN/CITY, in a NEIGHBORHOOD then. HOA is just ONE kind of version of your potential problems.

This is the legal guidance of those that would shatter our hobby: The International Property Maintenance Code

PREFACE | 2018 International Property Maintenance Code | ICC premiumACCESS
 
blewbyoutobad said:
Does the upper seal come out easily with the crank bolted up but the main cap off?
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FWIW.... Use a soft brass rod to tap the upper seal out of it's groove; that is the old standard way. Be ready to put a small hole in the seal end, and route a thin brass wire over the crank and through the small hole in the seal end to help pull it through. Loosening the other main caps a bit will help but you don't want to over do that and get a lot of angle pressure on the rods and their bearings and the front seal.
 
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