351M Rear Main Seal
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Freshman User
Joined: Apr 2001
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351M Rear Main Seal
Anyone changed one of these in the truck before. Mine is leaking like crazy. Truck has 103,000 mi on it. Is this a common problem? Any easy fixes? don't really want to spend high$$$.
Thanks
Thanks
Posting Guru
Joined: Aug 2000
Posts: 2,416
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From: PacNW
351M Rear Main Seal
[font size="1" color="#FF0000"]LAST EDITED ON 04-May-01 AT 03:31 PM (EST)[/font][p]I've never changed one on an M series in the truck before but it is a 2 piece seal so it shouldn't be all that difficult. The basic procedure is to remove the oil pan, loosen the mains so the crank can drop slightly, remove the rear main cap, drive the upper half of the seal up, around and out with a brass drift, lube the new seal up and install the upper half by sliding it around the crank, install the lower half in the cap and re-install the cap with sealer, then re-tighten the mains and re-install the oil pan. It's always a good idea on 2 piece seals to have the split offset from the cap/block mating surface to help prevent leaks in the future.
First however, I'd make real sure that it's the rear main leaking before I changed it. The oil pressure sending units are notorious for leaking on the 351M/400 series and oil runs down the back of the motor and can look like a rear main leak.
First however, I'd make real sure that it's the rear main leaking before I changed it. The oil pressure sending units are notorious for leaking on the 351M/400 series and oil runs down the back of the motor and can look like a rear main leak.
Lead Driver
Joined: Nov 2000
Posts: 6,646
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From: Albuquerque
351M Rear Main Seal
You could try a trick I use. I have a restrictor in the inlet for the PCV system. It causes the crank case to hold about 5 inches of vacuum. In my case it's for performance/idle uses. I completely blocked off the PCV intake air on a friends "T" bird that had lots of leaks and it stopped most of it. If the engine is old the vacuum in the crank case will pull air in where the leaks are and the oil back with it.
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
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Freshman User
Joined: Apr 2001
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351M Rear Main Seal
Thanks guys,
Hey beartracks, I might try that vacuum trick, only thing I see is possible sludge build up, but if it stops the leaks until time for rebuild, I'd rather do that and replace the seal later with the engine out.
Hey beartracks, I might try that vacuum trick, only thing I see is possible sludge build up, but if it stops the leaks until time for rebuild, I'd rather do that and replace the seal later with the engine out.
Elder User
Joined: Feb 2001
Posts: 829
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From: Porterfield
351M Rear Main Seal
OK
So this trick will work but think about this a minute. Now your sucking unfiltered air into the motor in a spot that see lots of dust... Just how long do you think your motors going to last.....You put an Air cleaner on your Carbs. for the same reason, to keep the dust out.
Here's a trick I was told to do for running a positive vacume in your crank case, put the rear seal in backwards this helps to keep the dust from coming in.
ShaZam
So this trick will work but think about this a minute. Now your sucking unfiltered air into the motor in a spot that see lots of dust... Just how long do you think your motors going to last.....You put an Air cleaner on your Carbs. for the same reason, to keep the dust out.
Here's a trick I was told to do for running a positive vacume in your crank case, put the rear seal in backwards this helps to keep the dust from coming in.
ShaZam
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