Rear main seal leak 351 cleveland

machclone71

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Ok guys need help.... I have replaced my seal 6 times 3 special felpro seals 2 direct rubber replacements and 1 rope with the needle. I replaced the crank and bearings put new intake on and oil sender and brand new oil pan. Still the same old crap. No leaks when cold then after engine warms up it is a constant drip. The only thing I have not messed with is the cam plug and oil gallies plugs. The previous owner rebuilt the engine and replaced those. I don't know if it was align honed or checked. What do I do next I have done oil dye with a light and it's all over behind flywheel so I can't tell about the cam plug or oil gallies. And no I am sure the seal was not installed backwards in case your wondering.

 

c9zx

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Some after market pans are not properly formed at the transition from the flat pan rail to the curved rear seal area which causes a leak. I have experienced small leaks at the oil passage plugs as well as the cam tunnel plug. I know it is a PITA to check but, after 6 rear main seals I think it's time to look. I hope you find the leak. Chuck

 

TommyK

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The first thing to do is eliminate all the plugs in the back of the block as a potential source as well as the rear of the intake, oil sender, pan etc...then assuming you are reasonably sure it is in fact the rear main seal:

Does it leak just idling once it gets warm or do you have to drive it to get it to leak?

What kind of crank was put in?

What is your oil pressure at idle and under operation?

 

machclone71

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Stock crank and the machine shop cleaned it up the same exact leak was there prior to replacing the pan and yes it is only once the engine is warm idling and driving did all this and no slowing of the leak nor making it worse just no change even before changing the crank back of intake and by sender and valve covers are dry and absolutely not leaking.

 

Jeff73Mach1

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Sorry your having this problem. Step one is to degrease and clean the engine until it is spotless, then you can see what is happening better.

First I would check . . . the valve cover gaskets, Even a weep there can travel down the block and look like it is coming from just about anywhere. If that isn't it (and I hope it is) then I'd check that it is not the intake manifold at the rear sealing surface. Slightly harder to repair, but still easier than another rear main seal. Make sure your PCV system isn't plugged as it will cause excess pressure in the crankcase and will cause seals to leak.

If after all of that, if it is indeed the rear main seal I'd pull the engine. I think there are a few things that need to be checked that would be hard to do in the car. Thrust of the crank is one, condition of the pan rails, checking of the cam plug and oil galley plugs condition of the crank's sealing surface(a repair sleeve is available I believe)

Good luck

 

machclone71

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Line bore? Seal to crank clearence? Anyone had experience with either of these issues.

 

Jeff73Mach1

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line boring doesn't remove enough metal to cause an issue. Seal clearance can be an issue if your crank has been machined improperly, but stock cranks should not have clearance problems otherwise. Some aftermarket cranks like the Scats do have challenges sealing with 2 piece gaskets, but that is an oddity that doesn't appear to be your issue.

Seals leak because of worn bearings allowing excessive crank movement. If that is the problem, you'll need to overhaul your engine to stop it.

 

rocket366

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like in the link I gave you originally;

Important that the mating lines of the two piece seal is offset

and not aligned with the parting gap of the rear main cap.

Also use sealer on the ends of seal and the main cap mating surface.

????

I have also read that people have had issue with a crank that has

hash marks on it for rope seal. They had the hash marks removed

by the crank grinder to get good results with the 2 piece seal.

xgjwp1.jpg


Paul

 

Omie01

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Something else to consider, but would involve engine removal and disassembly is having your block machined for a 1 piece rear main seal. I didn't know you could do it but my current engine builder asked me if I wanted this done, and I told him absolutely!!

 

Budbass

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Remember to remove the small tip in the seal channel that holds the rope seal from moving if you use a rubber two piece seal.

 

TommyK

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Another thing to check with a 2 piece seal is the seal crush. It has been reported on the 460 board many times that the seal ends are too long out of the box and need to be trimmed to establish a seal crush of about .020".

Here is a link that describes the issue in more detail.

http://www.460ford.com/forum/833630-post30.html

Perhaps I missed it but did you ever state what your oil pressure is?

 

machclone71

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I have done the clocking of the seal but I did not know about the hash marks on the crank causing leaks any tips on removing them without removing the crank. That is great NEW info I appreciate that all the other stuff I have heard and done so really thank you if you have more info on that issue from other forums or any where I would greatly appreciate it.

 

piper62j

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There is an oil pump primer shaft you can buy on EBay (cheap) to run the oil pump without running the engine. Pull the distributor (mark the housing and rotor first to retain the timing) insert the shaft and spin it COUNTER CLOCKWISE while watching below for where the oil is dripping from.. Of course, clean the area first.. You should be able to tell if the oil is dripping from the rear of the pan or to the front of the flywheel without it slinging all over the place. You'll need two people for this.

I've found in most cases that oil under pressure will drip from a bad seal whether the engine is hot or cold. It may be easier and less expensive to diagnose the leak this way rather than pulling the pan several times and replacing the rear main seal.

Just my opinion on what I'd do to begin the elimination process in the least expensive way. This procedure will also work very well if you have the tranny and flywheel removed to expose the oil gallery plugs..

 

rocket366

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If oil pressure can have an effect on a rear main seal leak please

educate me on how I have never heard of this.

Paul

 

TommyK

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If oil pressure can have an effect on a rear main seal leak please

educate me on how I have never heard of this.

Paul
Not sure if this question is directed at me but I don't believe it will. The original post indicated that the oil galley plugs were a possible source of the leak and excessive oil pressure will cause a leak there. That's why I asked about oil pressure.

As far as the knurling on the crank being an issue I have only ever heard this theory with regard to some scat cranks and factory cranks from reverse rotation marine engines which doesn't seem to be the case here.

 

Jeff73Mach1

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oil pressure does not cause rear main seal leaks, but crankcase pressure can. I had mentioned eariel to make sure the PCV system was in good shape for this reason. All engines have blow-by to some extent, and if the PCV system isn't proper, the front and rear seals will leak. When I bought my car, the PO had replaced the breather on one valve cover with a sealed cap. At higher RPM it would spit out the oil dipstick and the PCV valve and spray oil everywhere.

It is hard to drive at low RPM on the interstate with 4.10 gears- my buddy who drove me to pick up the car got a nice misting from driving behind me. LOL

 

secluff

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oil pressure does not cause rear main seal leaks, but crankcase pressure can. I had mentioned eariel to make sure the PCV system was in good shape for this reason. All engines have blow-by to some extent, and if the PCV system isn't proper, the front and rear seals will leak. When I bought my car, the PO had replaced the breather on one valve cover with a sealed cap. At higher RPM it would spit out the oil dipstick and the PCV valve and spray oil everywhere.

It is hard to drive at low RPM on the interstate with 4.10 gears- my buddy who drove me to pick up the car got a nice misting from driving behind me. LOL


That's where I would look the closest. Glad to see someone else experienced "Dipstick Syndrome"! Always heard size matters, so when I was offered a larger 4bl from a 428 Police Interceptor to install on my 71 "M", I jumped right on it. My original setup had a hose from the PCV valve(L/F valve cover) to a stub on the rear of the carb. The 428 carb didn't have that fitting, so I just removed the hose and valve. That's just more junk under the hood, and that's why they made regular oil filler caps, right? And that would also make me a member or the throw away club like my buddies that were throwing away all those Rochester carbs and rev limiters.

Didn't take but two days and I had oil everywhere. Oil was seeping from the rear and front seals, and the dipstick was actually pushing out of the tube until the hood stopped it. I thought the car was possessed. When one of the shop techs looked at my car and saw what I had done (can't print everything he said) I was made to understand "Crankcase ventilation"! :whistling:

 

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