Flathead Oil Leak

buck36

buck36

Junior Member
My truck was stored for several years and I have recently began to work on it. I was getting water in the oil. I pulled the heads and replaced the head gaskets and this seems to have fixed that problem. In doing this work I changed the oil immediately after replacing the head gaskets and prior to starting the engine. I also changed it again after after re-torquing the heads 3 times while allowing the engine to warm up and cool down over night between re-torquing.
I noticed that each time as I added oil that I would get a quite a bit of oil to drip out of the cotter pin hole on the bottom of my bellhousing. This volume of oil would cover an 10 to 12 inch diameter area on my drip tray under the truck.
This seems strange to me. The engine has always leaked a bit especially after running for a while.
My question is how is this oil getting out while I'm adding it.
Is it coming out the rear main seal or somwhere else.
Opinions , suggestions would be appreciated.
 
Most of these engines get over filled with oil. This is the main reason oil gets in the clutch housing and drips out the cotter pin. G.M.
 
I have a 36 pickup with a 21 stud motor in it. the old motor was a 21 stud motor also. when I got my pickup it had sat for 30 plus years. the story goes they put it in storage because the motor was tired, and tired it was. I put about 4,000 miles on it. in that time it started leaking a lot more oil then when I first got it. so I took off the pan and cleaned out the sludge, what a mess. then I replaced the pan gasket and put the pan back on. it can be done with out pulling the motor. is the truck the one in your avatar? the job took me about 3.5 hr to get off and a lot quicker to put back on. if I was going to do it again I would pull out the front axle. so after I put it all back together it leaked a lot less oil. as GM says maybe you just filled it up to much. my truck likes to seek it one level it likes about 4.25 qts. good luck...Brendan
 
buck36 said:
My truck was stored for several years and I have recently began to work on it. I was getting water in the oil. I pulled the heads and replaced the head gaskets and this seems to have fixed that problem. In doing this work I changed the oil immediately after replacing the head gaskets and prior to starting the engine. I also changed it again after after re-torquing the heads 3 times while allowing the engine to warm up and cool down over night between re-torquing.
I noticed that each time as I added oil that I would get a quite a bit of oil to drip out of the cotter pin hole on the bottom of my bellhousing. This volume of oil would cover an 10 to 12 inch diameter area on my drip tray under the truck.
This seems strange to me. The engine has always leaked a bit especially after running for a while.
My question is how is this oil getting out while I'm adding it.
Is it coming out the rear main seal or somwhere else.
Opinions , suggestions would be appreciated.
Click to expand...
What year is your engine? Flatheads didn't have rear seals untill 1946. All engine before this just had a slinger. If you over fill them thay will leak. If you stood the engine up on the flywheel end all the oil will run out of the pan. Walt
 
The engine is a 21 stud and I believe it is original to my 36 truck.
I only put 4 quarts of oil in it since I removed the filter when I replaced the head gaskets and I haven't reinstalled it yet. I was waiting till I got things all sorted out because it's kinda in the way. The level on the dip stick shows full with 4 quarts.
Is it possible that I have sludge built up causing the oil to drain out the back as I pour it in the fuel pump/vent stand?
 
My first question is what oil did you use when you added oil? Probably that engine was running straight 30 wt non-detergent oil I'm thinking and that's what should be added.

That being said, I've been down this road and learned alot by asking questions here just like you are. Here's a list that I was told to check and this was/is on a 24 stud but the principles shoudl remaint he same: the rear cam gear cover could be leaking, one of the plugs back behind the flywheel could be leaking (near the cam gear cover), the rear seal you put in for the pan may not have been installed just right and it's leaking, the oil filter line that comes out from the back of the block may be cracked down low or it's loose in the block, finally, once it's running and it leaks a lot after you shut it off, the crankshaft main and rod bearing surfaces may be out of spec.

My problem turned out to be the last one and this was a supposedly "rebuilt" motor. Yours may not be as it's leaking oil as you put it in. If you've gone through everything that you can do without pulling the engine and it still leaks, I'm thinking you will need to pull it and check things more thoroughly ...
 
My '36 pickup with a 21 stud motor developed exactly this problem, on pulling the oil pan it was clearly from the cork gasket at the back of the pan (between the pan and the flywheel/clutch housing that has the cotter pin); it had simply disintegrated from age allowing oil to slosh over and leak out. I was surpised by the amount of sludge in the pan, in an otherwise clean appearing/good running engine.

Adam
 
Sometimes the metal part of the top of the pan that seats down on the cork rear seal is bent. The metal runs off or close to the edge of the cork and leaks. I always make sure the metal is straight. G.M.
 
A misaligned gasket or edge on the pan makes alot of sense. This could divert the oil as it drained down to the back of the pan. Well it seems the pan is coming off. How hard is this with the motor in the truck?
 
buck36 said:
A misaligned gasket or edge on the pan makes allot of sense. This could divert the oil as it drained down to the back of the pan. Well it seems the pan is coming off. How hard is this with the motor in the truck?
Click to expand...


take off the upper rad hoses, fuel pump stand, starter, exhaust cross over pipe, exhaust on driver side maybe front wheels for ease of access. jack up motor as high as you can get it. remove the brake rods if you have them. unbolt the wishbone and loosen the u bolts, but at that time you may wont to remove the front axle it will be in the way. if you don't you need to pull the wishbone down as far as you can. if I where to do this again I would take out the front end at that point it is easy to remove. then take out all the bolts. there is one on the top on the starter motor side. you may need to rotate the crank so the weights will clear the pan. there is a service manual, it is green and has a photo of a V8 logo on it. it's for 32 to 37 or 36 cant remember, it tells you how to do it. one thing it says is not to deviate from the steps it will cost you more time. witch it will. the job took me 3.5 hr and 2.5 or so to put back together. one more thing, make shure that you clean your screen in your oil pump. it is a dirty greasy job but your old truck will like it good luck ....Brendan
 
The counter balance on the front cylinders wants to be in the down pesition or the pan is very hard to get off. G.M.
 
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