Leaking Center Main Bearing Nut

Billludwig

Billludwig

Junior Member
I'm getting a leak from the left side center main bearing nut. I'm new to these engines and wonder if it needs to be sealed, tightened, or just what. Suggestions?
 
I'm surprised to hear that. I don't know how that retainer nut could leak. I'm assuming you mean its leaking oil not coolant.
Also just wondering if the leak could be coming from the fill tube/cap.
If its coolant that its leaking then its probably a crack thats above that location.
 
If it's truely leaking oil up the bolt, then first make sure the engine can breathe properly. Make sure the oil fill cap isn't pushed on too far and bent the tangs.

To seal the nut I would clean it with gas and blow dry it, then brush some paint around the base of the nut. If you have the pan off to adjust the main bearings, then you could use sealer under the nut.
 
i have seen them leak on cars with excessive blowby but then again it blows out of everwhere's
 
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The filler cap is clean and unobstructed. I'm pretty sure it's leaking oil around the bearing nut, but there's a slim chance it could be leaking coolant from the water hose casting. I've cleaned the block thoroughly and will take it for a quick spin today and verify where it is coming from. More to follow...
 
If it keeps leaking oil after you check everything you can externally, drop pan and check your centre main. Mine was leaking oil at center main nut and it was caused by loss of torque due to bearing failure.
 
Billludwig said:
I'm getting a leak from the left side center main bearing nut. I'm new to these engines and wonder if it needs to be sealed, tightened, or just what. Suggestions?
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Hey Bill,
'new to these engines' :).
How long have you owned this engine ? Has it leaked all along or did you just notice it ? I'm wondering if you have added any oil to engine ?

At times, guys new to this engine, will put tooo much oil in engine...even after an oil change...not knowing that the dip tray holds a lot. A guy will put recommend quarts...and overfill. Thereby causing 'problems' like leaks !
And, overfilled AND blowby is cumulative causing even more problems !

Better to be a little under the full mark ...than to be above it,eh !
 
When the center main shim used on the left side is slotted like a rod shim, you may have problems with leaks. The main shims are suppose to have a hole for the main bearing bolts or a void will be created that will cause an oil leak. Slotting main shims is a bad short cut that could have been used when main bearing clearance was last set.

There is a modern main bearing bolt set that is now available from the venders. It comes with special washers that seal out leaks I've used them on the last two overhauls and like them.
 
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Hardtimes -- I just purchased this '30 Roadster, and have no history with it. I just verified that it is leaking oil from that nut (see pic). Also, the oil level is a little below the 'F' mark on the dipstick.

Purdy -- I'm assuming that the special washers that seal out leaks requires pulling the pan?? If so, I think I'll just try to live with the leak. Also, is that nut some kind of adjustment that I shouldn't mess with, or can I put a washer under it and tighten it? I can't find anything about it in Les's manual.

Thanks!
 

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Billludwig said:
Hardtimes -- I just purchased this '30 Roadster, and have no history with it. I just verified that it is leaking oil from that nut (see pic). Also, the oil level is a little below the 'F' mark on the dipstick.

Purdy -- I'm assuming that the special washers that seal out leaks requires pulling the pan?? If so, I think I'll just try to live with the leak. Also, is that nut some kind of adjustment that I shouldn't mess with, or can I put a washer under it and tighten it? I can't find anything about it in Les's manual.

Thanks!
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Two things that can cause a leak at that nut. One is like Purdy told, if the shim pack is slotted to make it unnecessary to completely remove the cap and bolt, it will probably leak. Second is if the bolt was never tightened to the proper torque value of 80 ft. lbs. Both scenerios require removing the pan and working from the bottom. The nut you reference is the nut on the bolt that holds the main cap in place and cannot be removed or tightened properly from outside the engine.

Sorry to be the bearer of bad news but it looks like the pan will have to come off to remedy this.
 
You can't remove the nut unless you pull the pan to hold the bolt head, that's why I suggested the tempory easy fix of cleaning it and putting paint around it. That should seal it.
 
I have seen this problem when a lock washer was used instead of a cotter key. If you have a lock washer, you need to pull the pan as stated above and go back to the cotter key.
 
Just drive it. If the leak in the picture is the only concern, you have nothing to worry about. You're not loosing oil from it.

Drive it and don't worry!!!
 
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