Serious oil leak !

[Nostalgic1930]

Hey guys looking to get some insight on this situation.

i have a banger motor in my 1930 truck. and after running about an hour or so it pours out about a half a quart out of the cotter-pin hole. i took the pan off and took 2 shims out and still didn't do anything!

the cap had a hole drilled into it and the pipe looked to be cracked and welded back on, my question is what else could cause this oil to be coming out in such an abundance.

is it that the babbit is worn down so much ?

looking to pull the motor and get away with the least expensive fix for now, which would be the bearings re done and crank re ground? would a Brass seal help as well. much appreciated !

also was told if the cap was from another car it would never be right or aligned correctly because of the specific wear pattern to the engine, crank, and bearings

[AL in NY]

Nostalgic1930, did you just take out two shims or did you determine that's what needed to come out by checking the clearances.

[Nostalgic1930]

i took out two and hand cranked the engine to see if it would turn free if i took out the third and ran no shim it wouldnt turn by hand

[BILL WILLIAMSON]

Is your oil cap pushed down too far, blocking the 4 square vent holes?? I did that once & it leaked like a sieve out of the bell housing.

[Nostalgic1930]

nope ran it without the cap same result

[James Rogers]

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How many shims are left on each side?

[1crosscut]

Is this a motor your familiar with and this is something new happening or is it a "new to you" motor that your running for the first time?
Did you change the oil recently and running to high of an oil level?
Most run midway between low and full.
Its possible the the weld on the tube plugged it up or it is screwed too deep into the cap not allowing the oil to drain.
Would you by chance be parking uphill on a steep grade after your drives?
It would be a good idea to get some plastigauge and see just what your clearances are.
Others will chime in I'm sure.
Dave

[Nostalgic1930]

i am not i bought the truck and i have been filling low to mid level with straight 50 wieght, so its not over filled, there is one shim left. and yes once i did park on an incline this past week and about 2 quarts came out , and i am serious

[Benson]

Originally Posted by Nostalgic1930

Hey guys looking to get some insight on this situation.

i have a banger motor in my 1930 truck. and after running about an hour or so it pours out about a half a quart out of the cotter-pin hole. i took the pan off and took 2 shims out and still didn't do anything!

the cap had a hole drilled into it and the pipe looked to be cracked and welded back on, my question is what else could cause this oil to be coming out in such an abundance.

is it that the babbit is worn down so much ?

looking to pull the motor and get away with the least expensive fix for now, which would be the bearings re done and crank re ground? would a Brass seal help as well. much appreciated !

also was told if the cap was from another car it would never be right or aligned correctly because of the specific wear pattern to the engine, crank, and bearings

Where is the hole in the cap? Is it in the "channel" (on the bottom of the cap) that runs up to the rear of the main cap. That is ... is the hole in that channel that goes from the 1/4 inch drain tube towards the rear of cap?

If this is where the hole is then the oil will run down into the flywheel housing.

Also if the pipe is cracked or has a leaking weld joint then air can be forcing oil out. Pipe must be about 3 inches long so the end of the pipe is always BELOW the oil level. This keeps the crankcase pressure from blowing oil back up the channel and out the rear main.


I have seen where someone removed the rear cap and drilled a hole from the crank side in the babbit straight down into the channel. I am not sure if this makes matters worse or not as long as they did not drill clear through to the outside of the cap.

Pictures might help the engine guys figure it out!

[1crosscut]

Doesn't sound promising. Most run a 30wt oil. Don't know if running 50wt would have much to do with it. 2 quarts....... dang.

[Nostalgic1930]

Originally Posted by 1crosscut

Doesn't sound promising. Most run a 30wt oil. Don't know if running 50wt would have much to do with it. 2 quarts....... dang.

literally flowed down the hill , i was speechless

[Nostalgic1930]

right in the center of the cap in the middle of that groove is drilled in but not all the way thru.

what are these Brass rear main thrust would those do anything

does anyone make a reproduction cap?

[Glenn C.]

The mounting surface of that cap in the picture is in very rough shape. I prefer to lap the cap on a heavy plate glass or ground slab of granite to obtain as close as possible perfect mating surface. Bill Barlow from Bend Oregon is the man for repair of the rear main bearing cap babbit. Bronze thrust seal works great, but you need to pull the crank to install it.

[James Rogers]

Originally Posted by Nostalgic1930

i am not i bought the truck and i have been filling low to mid level with straight 50 wieght, so its not over filled, there is one shim left. and yes once i did park on an incline this past week and about 2 quarts came out , and i am serious

With only one shim left, it sounds like it is time for some bearings. You also need to measure the thrust clearance. If the thrust is more than .015 you will have a leak which will be more with more clearance. Thrust clearance leaks have a tendency to leave a trail because the crank moving forward and back create a pump effect and leak profusely. If the thrust is within tolerance (.003-.012) you probably just have worn bearings. When the bearings get worn and all shims are removed you get an egg shape bearing with the top and bottom tight to the crank and the sides well out of tolerance causing a channel for leakage. The hole drilled in the is an old bandaid fix for a leaky rear main and some previous owner knew about the condition.
If it leaks that bad with 50W you have a very worn bearing. Here is a picture of a main with a common hole but this is done at rebuild. Some builders do this as a preventative measure. I believe if a builder has no more confidence in his work than this you should find another builder. The groove in the second pic should connect with the wells at the sides to be fully effective. There are more "fixes" but I won't go into those since they don't apply to this thread.

[Nostalgic1930]

my question now is , will it affect anything if i try and use another cap off another car, since the oil tube was welded, after the engine has new bearings, and crank reground i would hate to use a cap that might have a different wear pattern. thanks all for the help!

[James Rogers]

Originally Posted by Nostalgic1930

my question now is , will it affect anything if i try and use another cap off another car, since the oil tube was welded, after the engine has new bearings, and crank reground i would hate to use a cap that might have a different wear pattern. thanks all for the help!

Some have gotten away with it. Normally, the tube is welded on all rear caps when the engine is rebuilt. Some builders don't but I do so it won't fall off. Just about all I have ever removed have been welded.

[Duffy1]

I used J B Weld on mine tube . Will J B weld keep it in place ?

Thanks

[columbiA]

The main cap in post #12 appears to have a score mark on the RH mounting surface close to the bolt hole.Unless the surface is perfectly flat,it will leak oil.In the1949 FOMOCO of Canada parts book,it lists the 3 main caps as "standard-finished" with rear main babbitt length of 2.995".I have quite often used caps from other engines & had no problems.If your crank is.010 US for instance,then you need a cap of that size

[JBohannon]

I am curious about the use of 50 wt oil. I have an oil leak if I go over half full not near as bad as his. If I went to 40 wt or 50wt would that help. Thank, Joe B.

[JBohannon]

Will 40 or 50W still lubricate well.