The Stovebolt Site Forums The Shop Area Engine Shop Oil leak on a 235

I orginally posted this on "Chevy Talk" and was also recommended to this site. I have a 1955 Chevy 3200 with a 235 that is leaking oil, but in an odd way. No oil leaks out when the engine isn't running... when the engine first starts up no leaks either, but after about 20-30 seconds or so a steady drip of oil starts to appear from the hole of the pan under the bellhousing. This will continue while the engine is running. When the engine is stopped, oil gushes out from the hole for a few seconds, then stops completely. I have heard that it maybe the rear main seal leaking, but I wanted to find out for sure. If it is, are there ways to fix it without having to pull the entire motor, or even pull the oil pan off? I just joined this forum and would love any feedback that anyone has to offer. Thanks!

Hi Milhouse,

Welcome to the nuthouse! Somebody recommended us to you? What a sicko.

Your oil leak is appearing at the bellhousing dust cover, eh? Typically that is the rear main leaking. The 235s are notorious for rear main leaks. However, yours sounds excessive. That much oil could be from the rear main, the rear oil galley plug if your motor has hydraulic lifters, or running down the back of the motor and coming out the dust cover.

You can remove that dust cover and look into the bellhousing. If the front of your flywheel looks like its spinning oil off and splattering it inside the bellhousing, its likely the rear main. If you're feeling brave, you can remove the dust cover, chock the wheels, and let the engine idle while you watch for where the oil is coming from.

If the back of the motor or the inside front of the bellhousing is oily, it may be the oil galley plug leaking. The oil runs down the inside of the bellhousing and out the dust cover. A severe valve cover leak, or a leaky external oil line that runs near the back of the motor could do this too.

I have also seen over-filled standard trannys puke fluid out of their input shafts. It looks like an engine leak, but the tranny just has too much oil. The auto trannys can pump their fluid out too, if the front tranny seal or front pump fails.

What is the history of the engine? How many miles, how long have you had her, what kind and weight of oil do you use, what is the oil presssure, etc. We're here to help.

Good luck

Chiphead

Thanks for the advice Chiphead!

I bought this truck just this last summer, so I'm still learning more about it. It was one of those offers that I just didn't want to pass up... maybe it was a mistake, but so far I'm still pleased. As far as I understand the truck was originally used at a lumber yard, then sat in a barn for years. After that a junkyard bought it, ran it around their property, and let it sit for a few more years, then I came along and bought it. So far I've redone the brakes (rebuilt the master cylinder, replaced some lines, rebuilt the wheel cylinders), tuned up the engine, and started repairing the cab's floor and fenders. I'm not sure what weight oil is in there right now, and I haven't changed it because I want to find out the source of the leak first. The truck has around 75,000 on the odometer (I'm not sure if that is 75k or 175k). Right now the engine runs extremely smooth, and it really frustrated me to see that oil leak out like that. Currently I'm a junior in college, so during the school year I'm only able to make it back to work on the truck (and my coupe) about once every month or so, plus I'm unable to store them in a garage at this time. At the current time the truck needs the fenders fixed (welding, bondo, and some paint), and the cab floors need to be patched up some more. After that the windshield needs to be replaced (which I was able to get a new one from the yard for it), and the wiring needs to be gone over. I like to think that it isn't too much work, but sometimes I'm a little too optimistic I'd love to get it on the road soon to actually be able to drive around town, but it most likely won't be until next spring or summer (especially depending on what the leak is).

I didn't mean to type this much up, but I'm glad to be able to share about my truck! Any more recommendations or tips anyone has would be greatly appreciated. Thanks again for the help!

I forgot something. To change the rear main seal, you do have to pull the oil pan and the rear main bearing cap. The 235 has used 2 different rear main seals over the years. The 235 1st series from 53-55 used a rope seal. The NOS asbestos work the best, and are available from Stovebolt Engine Co. The 235 2nd series '55-62 used a 2 piece rubber seal. Its available at NAPA. The rubber seal is easier to install.

Since '55 was the crossover year, some trucks were built with the 1st series 235, and others with the 2nd series engine. Someone could have installed the wrong seal at some earlier time. If your engine has the 4" diameter water pump pulley, its a 1st series. If its got a 7" diameter water pump pulley, its a 2nd series. There are many technical differences between the two engines, so some parts will swap and some won't.

Have you made sure your motor is a 235? Some Chevy trucks came with a larger I-6 called a 261. It looks very similar to a 235, but its got a full-flow oil filter and other differances. Post the block casting #s to ID what engine you have. The numbers are on the pass side of the block, near the motor mount or the vent tube behind the fuel pump.

good luck
chip