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Discussion Starter #1
Ah yes, my favorite topic! I've been plagued with an RMS leak for some time. I've replaced the seal twice, but still no luck. I've got the engine out for a winter upgrade (Trick Flow top end kit, plus some other stuff) and want to make sure I fix the leak, once and for all.

BTW, here's my upgrade site:
https://sites.google.com/site/sandgboyd/steve/2010-engine-upgrade-projec

The last time I replaced the RMS, I didn't notice any problem with the leaking seal, so I added some RTV to the seal seat and the rear main cap, for insurance. Didn't help. I have also replaced the PCV valve. Tomorrow I'll check the bearings and the seal and hopefully will find the problem.

Question: Can insufficient ventilation at the valve covers cause crankcase pressure that could blow oil past a perfectly good RMS? If so, should I put in a valve cover vent (in addition to the line from the oil fill neck to the throttle body)?

I've also read that a bad rear main bearing can result in a leak, but I don't see how. Any other ideas?

Thanks
- Steve
 

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Use the FMS seal, PN 6701-B351. It's the easiest to install correctly, and makes the best seal. Install it on the end of the crank before you put the main cap on; it's much easier that way.

Keep in mind that every oil leak anywhere on a SBF appears to be a RMS leak.

In theory, too much oil pan pressure can blow out the rear seal. But it usually comes out somewhere else, first. Like the dipstick. So, if your dipstick stays in place and isn't popped up, then that's not the issue.
 

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Discussion Starter #3
RMS leak

It's definitely not leaking at the dipstick. I'm familiar with the fact that 302 oil leaks all seem to work their way to the back of the engine. So, I cleaned the engine, put in some UV dye and drove the car for about a mile before pulling the engine. The engine is on a stand, so I've got a good view of it. Fresh oil with dye had clearly run from the vicinity of the RMS down the front side of the bell housing cover shield. There is also evidence of oil inside the bell housing. Just looking at the RMS, I can't see any problems with it. I've tried several oil pan gaskets - including one piece rubber, both with and without RTV - and don't see any evidence that this most recent one is leaking. There doesn't seem to be any freshly leaked oil anywhere but below the RMS.

I'll pull the rear main bearing cap and the RMS tomorrow and look them over closely.

I'm open to any suggestions... the one thing I don't want is to put the engine back in the car and still have a leak. If anyone has any ideas, please let me know.

Thanks.
- Steve
 

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You shouldn't need more ventilation with the proper PCV system working. Make sure the hose to and from the new PCV valve is clear.

A worn rear main bearing will lose more oil out of the bearing in the vicinity of the rear seal. How is your oil pressure? If the rear bearing is worn I would think the same is true with the other bearings. Any indication of burning oil and how do the spark plugs look? More oil from worn bearings (connecting rods) will get too much oil onto the cylinder walls and some will end up in the combustion chamber.

Make sure you take a close look at the crankshaft surface where the seal contacts it.

Bob, I'm going to be putting a new oil pan onto my '97 Explorer engine with 60,000 miles. I've thought about replacing the RMS at the same time. I'm thinking it would be good to remove the rear main cap to visually inspect the bearing and replace the rear main seal at the same time. Thanks for the tip on the FMS part.

Edit: I just looked up that part # that Bob listed and it is for a 351W block manufactured after 6/1/1993. The correct # for Steve's 302 would be Ford Racing #6701-B302. It fits 302's from 1983-2001.

George
 

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Be sure to check your engines intake manifold gaskets for leakage. Especially the "cork" end seals. These will move often when the intake is installed in the car. I like to use the cork end seals. (no silicone) However, i like to use 3M weather strip adhesive on them. I then clean the gasket surface to eliminate any grease/oil and then place a layer of the weather strip cement on both the gasket and the block. Then, after that "tacks up" on the gasket and the block side i then put the gasket on. I then let the gasket sit there for a long time before i install the intake manifold. This will allow the gasket cement to dry, and not allow the intake to dislodge it. These intake gaskets can and do simulate leaking rear seals very well..

If the problem isn't the rear manifold gasket, then perhaps the crank shaft is under sized in that area or, it is possibly leaking out of one of the fly wheel bolts?
 
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Steve, I had a persistent rear main leak in my Panoz 302 engine. After reading quite a bit about it, I put a bottle of Bar's Leak Reak Main Seal Repair in.

It fixed the problem.
 

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Are you putting sealer on the flywheel bolts? These are through holes that will leak if they aren't sealed. Also, is there a chance that you have a groove on the crank where the seal makes contact? I have used something from Fel-Pro called a crank saver (or something like that) which is a thin sleeve that gets installed over the hub where the seal makes contact. It's not easy to install but it worked for me.
Good luck!
 

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i have found that

a lot of leaks that seam like a RMS tend to point into a different direction, like a POS valve cover gasket.
the ones on mine wick oil enough to work its way to the lowest point the block plate at the bellhousing..drip drip..looks like a RMS
the edlebrock valve cover is going in the trash, when the engine goes back in next month felpro vs13264t will be installed, and i hope no-wicking of oil:001_rolleyes:
the same holds true for anti-freeze leaks start at the top and use a good pressure testing tool.
when i installed my RMS when building the engine i used a good ford seal and used "Hylomar Universal blue racing formula" gasket & sealing compound.
if you are taking the engine apart then make sure the seal is done well on the rear main cap, and of course the best bang for the buck "clean, clean, clean"
 

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I had a leak also same location,I replaced rear main,value cover gaskets,oil pan gaskets, to find it was coming from timing cover,I just tighten and no more leaks,that oil gets pushed around and seems to be coming from places it doesn't look like it does.
 

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I had a 302 that kept getting oil on the clutch & causing it to chatter . After much cussing & replacment of parts repeatedly , I thought at one point that it was the cam bearing bore plug . At any rate sealer on the flywheel bolts , or rather lack of sealer was my problem. Good luck,
 

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Discussion Starter #11
I used sealer on the flywheel bolts, and there's no evidence of oil on the clutch side of the flywheel - which is why the clutch hasn't been acting up. I don't see how oil could get from the timing cover to the back of the engine so fast (a 4 minute drive around the neighborhood) without leaving a visible trail, but a couple of the timing cover bolts were loose when I took it off, so I'll assume that's a possibility. Valve cover gaskets looked okay - no sign of leaks there. One really odd thing, though... when I took off the upper intake manifold, there was some oil on the gasket. I have no idea how it could have gotten up there. This engine seems like a oil sieve, probably due to being assembled by an incompetent engine builder... oh wait, that was me!:w00t:

Thanks to everyone for your suggestions.

- Steve
 

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I have heard of a few builders having issues with the rear oil gallery plugs leaking, (although it seems pretty rare). You can't access them unless you pull the bell housing.

If you have replaced the RMS twice already I would really look at your crank for wear at the point the seal lip touches it. Apparently there is a sleeve you can purchase to prevent this, without replacing the crank.
 

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Oil Leak

I've had the rear seal leaking too. You might want to check where your PVC valve as it goes into your manifold. Underneath the rubber grommet there is a screen that sometimes gets plugged.
 

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Crank Saver Sleeve

Has anyone tried to install a crank sleeve to solve a RMS leak while the engine is not apart? I was thinking of stripping the back of the engine down, clutch and flywheel removed, and sliding a sleeve on without removing the pan, etc. The engine is a 1967 Mexico block.
What do you think?
 
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