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old-tank

How to stop rear main seal leaks

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How to stop rear main seal leaks

I have worked with early 322 nailheads and one 47 straight-8, so yours should be similar. Some of this can also apply to other engines with rope seals.

Some assumptions: You know how to get to the rear main bearing cap and remove it and you know what a rope seal is. The engine is in the car and the crankshaft is installed.

Do not remove the upper seal. If it is not now absolutely flush take a portion of the used lower seal and stuff in the gap with a suitable tool. It is ok if it protrudes some. Take a 12 inch length of heater control wire, sharpen one end and install it into the groove that the upper seals sits in using a 6 inch length of brake line to keep it from kinking. Using vise grips push 1/4 inches at a time until it shows up on the other side. Install 2 pieces. Cut the wires flush with the block.

For the lower seal that goes in the cap take the piece that is supplied for that engine, bunch it together and flatten it and place it in the groove in the cap. Bunch it some more to make it fit while pressing it into the cap with a piece of exhaust pipe about the same diameter as the the crankshaft journal. Never cut or trim a seal to make it fit. It is OK and desirable if some seal protudes from the cap. (For situations where the crankshaft is out of the engine, remove this seal from the groove in the cap and place it in the groove in the block; repeat for the lower seal.) Fold any stray strands of the seal to the center so they will not get caught between the

clamping surfaces. Install the cap and torque to specs. Remove the cap and trim any stray strands that got clamped. Put some gasket sealer on the clamping surface of the cap. I use an anaerobic sealer. Dribble some engine oil on the seal only until it is saturated. Install and torque to specs.

To seal the groove in the sides of the cap I take some cotton twine coated with some No. 2 Permatex and hammer it to stuff it tightly in the groove using a large flattened nail until it is level with the top.

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(sorry about that wormy guy in the last picture --- hard to get good help these days...besides someone has to supervise and take pictures)

Willie

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Willie, I have replaced one seal a long time ago. The part of your proceedure I am having trouble imagining is where you say to bunch up the lower portion and then flatten it and place it in the groove. I assume you are pushing the seal together from the ends to bunch it up and then flattening it with the exhaust pipe as it is worked into the groove, or are you flattening it on the bench and then placing it in the groove?

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Willie, I have replaced one seal a long time ago. The part of your proceedure I am having trouble imagining is where you say to bunch up the lower portion and then flatten it and place it in the groove. I assume you are pushing the seal together from the ends to bunch it up and then flattening it with the exhaust pipe as it is worked into the groove, or are you flattening it on the bench and then placing it in the groove?

Bunch as in pushing the ends together; flatten enough to get it into groove, then flatten at 90* with pipe...this will give a wider sealing surface.

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seal4.jpg

(sorry about that wormy guy in the last picture --- hard to get good help these days...besides someone has to supervise and take pictures)

Willie

You are crazy! That guy knows what he is doing, is good with tools, is just freaking hilarious to be around and is exceptionally good looking.

just sayin '

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The above is helpful. Now for a question. What is the procedure to remove the oil pan. I have a '56 Century 2dr ht. My rear seal leaks and am thinking on trying to fix it. Also, what is your thinking on replacing it with a new style seal that I see advertised.

I am also going to check the filter to block gasket.

Thank you for the help and advice.

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The above is helpful. Now for a question. What is the procedure to remove the oil pan. I have a '56 Century 2dr ht. My rear seal leaks and am thinking on trying to fix it. Also, what is your thinking on replacing it with a new style seal that I see advertised.

I am also going to check the filter to block gasket.

Thank you for the help and advice.

If your car has single exhaust, remove the crossover pipe, detach the idler arm at the frame and let it hang (tape so that the idler arm does not rotate), remove oil filter, remove pan, remove oil pump. While it is apart, check clearances on the rear main bearing --- journal with plastigauge, end play or thrust with a dial indicator --- no seal will work if the rear main bearings are worn (hard on a dynaflow too).

I tried the 'new' two piece lip seal and it was a failure...leaked 2 quart in 10 miles...had to remove the engine to do it right.

Willie

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Thank you very much. I have dual exhaust so it seems pretty straight forward. First Buick I have owned so little tricks hare helpful, not to mention saving time. I will study your pics above. I can get the rope seal at NAPA along with pan gasket. I have a model 66R.

Thanks again,

Bruce

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...I am also going to check the filter to block gasket.

....

If you are talking about the "filter mount to block gasket" you should note that is a stamped steel gasket, similar to the head gaskets. If you do not have the steel one, and if the mount is not leaking, I would not recommend removing the filter mount. However, I find that the filter canister to mount gasket, which is a fiber style gasket, will leak if the car sits for a few months. Usually snugging the bolt holding the canister on will stop that leak.

And by the way, I have incorrectly assumed for years that my rear main seal was leaking when in fact it was the canister to mount gasket.

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I do have a gut feeling that it could be coming from the filter, I have a '61 Corvette that I converted to canistere to stop leak problems. My thinking is to install the canister adapter (open for thoughts and comments) first to see if leak stops.

I will inspect leakage on the block, I also have an engine gasket set. The car runs great (lifters sing when starting after sitting for a few days of sitting), other then that it runs great. Now stopping, that is a different issue, I have been reading the threads about breaks. We took the drums off and wear was in the center half of all of the shoes. I will keep followup on the brake thread. At least my right leg is getting stronger!!

Thanks for the input, much appreciaated

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I forgot to mension that I took off the inspection cover and put he car up on my lift and I did get a few drops of oil from the bottom of the main cap, now the engine was warm and was diven 5 miles prior to my inpection. Having a hoist makes this project a lot eaiser. The seal of the inspection plate to block and trans is very close fit. Part of my problem was building up a reserve and then leaking when sitting still. Also, the pass side of the engine by the oil filter is wet.

Thanks for the help.

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Glad to offer my opinion. I also had thoughts about the filter conversion but I kinda like that great big oil filter that was original equipment. As long as I can tighten mine and stop the leaks I'll be keeping it.

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I am a purest type of guy, would rather use OEM, but I would rather drive the car and can always to back to the origonal filter. For the price it is worth eliminating the filter as a leak problem. I have a '61 Corvette fuelie that I bought in 1968 that is origonal except those items to make it run today on today's stupid pump gas. the other is a '38 for street rod with and LS1 notor, so the computer takes care of the ethinal bull s...!

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Rear main leaks will tend to have more oil on the passenger side. Be sure it is engine oil and not transmission fluid. On my last cross country trip I had a puddle at the rear of the engine when parked; it looked like engine oil and I thought that it was from the seal that I had repaired a year earlier. A slipping transmission that was low on fluid had me looking a little closer. After the transmission leak was stopped it was dry again.

How bad is the leak on your car?...puddle size, amount of oil on frame, back of car,etc.

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Thanks for the comments.

The oil is on both sides of the block and is oil color, I do see red, but not a lot. I did take off the inspection plate and looked at the converter area and it was dry. I do not out rule the trans. Oil is being flung to the rear with oil burn marks on the exhaust. If I let it sit overnight then I get a puddle of about 2". So far the plan is to gather info, put a pan under the car and check the type of oil. I will be looking closer at the oil in the pan to see if it is red. This is my first Buick, all of my other cars have been chevys.

The car runs out great, rides great, handles good for the year, and fun to drive. The only problem is the oil leak. Fun to drive to car shows. Color is like yours except it is a HT. Next week will be more investigation. I need to check the Trans oil, did not think of that.

Thanks for the help.

Bruce

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Thanks for the comments.

The oil is on both sides of the block and is oil color, I do see red, but not a lot. I did take off the inspection plate and looked at the converter area and it was dry. I do not out rule the trans. Oil is being flung to the rear with oil burn marks on the exhaust. If I let it sit overnight then I get a puddle of about 2". So far the plan is to gather info, put a pan under the car and check the type of oil. I will be looking closer at the oil in the pan to see if it is red. This is my first Buick, all of my other cars have been chevys.

The car runs out great, rides great, handles good for the year, and fun to drive. The only problem is the oil leak. Fun to drive to car shows. Color is like yours except it is a HT. Next week will be more investigation. I need to check the Trans oil, did not think of that.

Thanks for the help.

Bruce

WHAT? I can not believe you even TRIED driving without checking the transmission. Poor thing.

Ben

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Some days, as we age, we get to focused on drips and make assumptions. Since the car went forward and the fluid was oil, not redish, I was thinking of engine oil. But as we get older and wiser one does not attach the problems thinking they know the cause. With the age of the computer and friendly people, a wealth of knowledge is avaiable. So we do not think of everything, but opinions and information are helpful.

How was that for an answer full of BS!!!!!!!!!!!!!!!!!!

Also, does anyone know of someone that works on Buicks in SW Florida?

Bruce

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Update, removed pan, rope seal was spinning in the block and cap. Replaced with Felpro new "rubber" seal. Clocked the seal about 10 deg. Had a devil of a time getting the driverside side cap seal in, also nail was very difficult to install. Waited overnight, put oil in and . . . drip, drip, drip. Drained oil, removed pan, removed bearing cap and inspected seal. installed same seal without clocking it. Measured side dovetail and driverside was .042" less deep then other side. Check seal blocks, one was .020" thinner. Milled the "dovetail" .020", installed bearing cap with RTV, inserted nails, cut off excess material. Torque cap bolts, assembled balance of parts. Let sit overnight, put oil in . . . NO DRIP, NO DRIP. Left inspection cover off and drove for 10 miles. Drove car on hoist and drip, drip. Cleaned oil off frame and housings, wife in car, hoist up, she started engine . . . no drip, rev motor up and hold at 2,000 RPM, no drip. . . let wife get out of car.

Most oil was on pass side. Oil filter inspection showed no leakage. Oil drops on the heat riser, just below dip stick. Dip stick very loose when seated, also no felt, or gasket on the retainer.

My feeling is when going down the road, oil from the dip stick hole was being flung out. I hope someone else has experienced the same problem and fixed it. I need to make a seal. fixing the dip stick slop was easy by bending the top area to provide friction to prevent dip stick from rising under pressure.

Has anyone experienced a blocked road draft tube? That could cause excess internal engine pressure forcing oil out at the dip stick? How do you check road draft tube?

Thanks

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Service the valley cover : http://www.buickrestorer.com/valleycover.html ...that would be the source of draft tube obstruction. Excess blowby from worn rings will cause this: with the oil breather off one valve cover rev the engine and if there should only be a small amount of vapor emitted...if it shoots back into you face then there is blowby; engine rebuild needed.

Willie

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Old-Tank,

I removed the valley cover and had no problem with air moving in or out of the road draft tube (used mouth method). I have attached pics of the valley cover and inside valley area. Engine is extremely clean.

Any ideas on what is next? i will check the actual road tube, but it is unlikely that is clogged.

Suggestions appreciated.

Bruce

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Question, e-bay has an adapter (3 pieces) to convert to screw on filter, this would eliminate oil filter leakage. Do you think i should purchase it. $60 for it. I have spent more in gaskets than that so far!

Bruce

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Service the valley cover while you have it out:

videos 10, 11, 12.

I have never used the adapter, but heard that they work as designed. I also have never had more than a small drip from the stock canister, so I would think a large leak like you describe is not likely unless it is the gasket that mounts it to the engine, and in that case the adapter would not help.

I have noted that the rear seal leaks very little with the car stationary, but will leak when driven, especially if driven up a steep hill (oil to rear of pan). The one time I tried the rubber rear main seal it was dry until I went on a 20 mile drive that resulted in the loss of 4 quarts.:eek: I have never heard of a successful seal with that type of seal.

Check for oil leaks between the head and the block. Oil moves through the head gasket to supply the rockers; oil drains back around the pushrods...poor sealing here with steel shim type gaskets will allow oil between head, block and gasket.

Willie

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Thank you very much for the comments. I have attached photos of the rear main seal that I took out, side shot with wire cover off to show dry area, it that is where you indicated a head leak could happen. The seal that I first took out was clocked about at the 8 o'clock position. The mushroomed seal was in the top, but I think it was turning, as I pused the top out with my finger and then a plastic punch.

The one thing that buggs me is the oil on the heat riser just under the dip stick . . . the dip stick problem has been corrected.

I tend to like to change one thing at a time, my labor is cheap! let me know your thoughts on the below plan.

1. Take your suggestion and clean valley pan prior to re-assembly, then test drive car. If oil leak is present then,

2. Remove oil filter to block adapter, install new gasket, test drive car. If oil leak is present then,

3. Check for oil around oil filter canister (to date when I check that area it is fairly dry). If oil leak is present then,

4. Change to spin on oil filter. If oil leak is present then,

5. Change rope oil seal, which more than lilely I should have done first.

Sound like a good plan? If you think I should just go to #5 let me know.

Thank you, Bruce

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Service the valley cover then get a "uv oil leak detector" (google). You're getting too much exercise and you're making me tired!:cool:

Willie

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