Rear Main or Oil Pan Leak? GM L6 250...

[DukesFin]

Okay, I know I've got oil leaking from low/rear of motor. Before I pull the motor (I know I have to anyway), does anyone have an idea how I might find out which location the oil is coming from? I have a feeling that given the rear of the oil pan being right under the rear main seal, there is no way to tell.

Including the question of figuring it out before I pull the motor, how about figuring it out AFTER I pull the motor? I just hate the idea of removing the rear seal if it is good...

Hmmm?

 

[Don S]

Re: Rear Main or Oil Pan Leak? GM L6 250...

I set them on block and run em on the floor. Hook cooling water to the engine where it normally comes in, add fuel and a battery and off you go.

If it's the rear seal, it will be coming out from behind the flywheel. If it's the pan, you should be able to wipe it off and it will start leaking again if it's below the level of the oil.

 

[WillyBWright]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Have a look at your valve cover gasket first. If it's leaking in the back (where most of the oil gravitates to), oil will creap down the back of the motor and drip down where you'd think the source was the rear main seal or oil pan. Generally speaking, if the flywheel area is dry, that eliminates the rear main seal. But if it's oily in there, it could be oil from a leaky head gasket or a leaky valve cover gasket finding its way in there (not real likely, but not impossible). Most of the oil from those sources would travel on the outside of the bell housing.

 

[Bondo]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Ayuh,.....

When chasing Oil Leaks,.....
Always remember that you have Gravity working For you......

Look Up from any leaked fluids,+ continue moving Up, til you find Dry areas......
The Problem is usually within a Inch or so from the Top of the Dampness.....

It's Easier in a Boat, as you don't have a Fan scattering everything all over......

Once you have it on the Floor,..... it should be pretty Easy to find........

 

[DukesFin]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Thanks guys... First place I looked was my valve cover gasket, and we're all dry up top. (Took 2 applications of a gasket when I built it to get it right!)

I like the idea of running it on the floor... I'll give that a shot...

Anyone know where I can find a new oil pan? Since it's going to be out and off of the motor, I might as well replace it... (new motor last year and oil pan was taken off of the old motor.

Another question... If I ran it in the boat, while engine is level in the driveway (water hose hooked up of course), do you think that if (given gravity and all), if it were the oil pan, I wouldn't see any leakage? Just thought of that now.

I am thinking that when I take off on the water, bow comes up, oil flows to the back of the pan, high, possibly allowing leakage then...

What do you think?

 

[Haut Medoc]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Possible.....
Get in there with a mirror & a flashlight....
You may be able to see it.....JK

 

[Silvertip]

Re: Rear Main or Oil Pan Leak? GM L6 250...

If it were mine, and as long as the engine is on the stand with the pan off, why not replace the front and rear main seals. You'll never have a better chance. If its a high hour engine have a look at the bearings at the same time. Button it back up and you no longer have to worry about whether you actually fixed the problem. Much easier than removing the engine twice.

 

[ManOfwar690]

Re: Rear Main or Oil Pan Leak? GM L6 250...

ebay for oil pan if your not in a hurry

 

[DukesFin]

Re: Rear Main or Oil Pan Leak? GM L6 250...

ebay for oil pan if your not in a hurry

Spring is coming!!!!! (Well, I don't think Winter will ever make it here in Georgia)...

Very low hours on the motor, so I am suspecting the oil pan, but if that's not it, it is definitely the rear main.

Thanks for all the help and input!

 

[bruceb58]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Could easily be caused by rust eating through your pan.

Just takes one chip in the pan paint, a little salt water....


...and some time!

 

[DHPMARINE]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Anything and everything is possible,but new engine/old pan last year .... why is the rear main on the suspect list?

DHP

 

[DukesFin]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Since I have narrowed the location of the leak to the rear of the motor... Also not coming from head/valve cover, etc.

Since I have to pull the motor, regardless of which location the leak is coming from, I might as well suspect every location possible, given the location.

I'll tell you what, finding an oil pan for a marine GM L6 250 with the dipstick on the starbord side is proving to be difficult!!!!

 

[Silvertip]

Re: Rear Main or Oil Pan Leak? GM L6 250...

There is a solution to every problem (usually)! If the search really runs to a dead end, why not just find a pan regardless of dipstick tube location. Cut the tube out of the existing pan after measuring its location, then have a metal shop cut the required slot in the new pan and weld in the old one. Prime and paint and away you go.

 

[Gary H NC]

Re: Rear Main or Oil Pan Leak? GM L6 250...

ebasicpower.com has a bunch of oil pans...give them a try.

 

[DJ]

Re: Rear Main or Oil Pan Leak? GM L6 250...

Why don't you put some dye in it and run it. It has to come out anyway.

The dye wil tell you as soon as you get it out. As stated, fluid runs downhill. No dye around the rear main? There's your answer.

That's allot safer tha running it on the floor.