After buying this m1078 i noticed it had a slow leak from rear driver oil pan corner it looked like. Had two large truck places check it out and both said rear main seal. But that didn’t seem like it to me. After digging in the TM I found the fording drain for the bell housing. I took the cap off and got less oil out of the drain then leaks out on a daily basis from that area. Maybe 4 tablespoons with. So I put the cap in the storage bolt and drove it for about 1.5hrs. That way it would warm up well and maybe be more prevalent where it is coming from. I was able to chase some oil pools up to the back of the engine. All around the bell housing upper vent. I see a hose exiting the back of the engine below the head. Is that an oil line? That’s the only place that could be possibly heating up and spraying under load causing it to show up in these different places. The pacbrake actuator is covered in oil, I say some drops next to that drip off the intake pipe. That fitting is also centered in the area where it can run down both sides of the bell housing and making the mess below. Do any of these pictures show anything to you seasoned aficionados? The last pic is the fitting I’m wondering about. It’s just above the pacbrake actuator. That’s its plug in the pic.
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M1078 Oil leak tracing and making me nuts
- Thread starter JRKJeeper
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Looks like probably rear main to me. Oil being flung around the bell-housing by the flywheel, wicking it's way through the breather fitting, etc.
Clean everything with brake cleaner and add UV dye to the oil. Get an inspection camera and pull the starter out so you can look in there.
But really these engines don't have a lot of oil leaking problems and more than one owner has experienced rear main seal failure. Add to that two shops have already diagnosed it as such. That's two opinions from direct inspection, not an unknown failure mode for this application, and you said yourself that 4 tablespoons worth of oil came from inside the bell housing from the fording plug....... not only does it look like a duck and quack like a duck - it smells like one too.
But do the UV test after cleaning - pull starter and use half a case of brake cleaner through every orifice and get your inspection camera ready.
Clean everything with brake cleaner and add UV dye to the oil. Get an inspection camera and pull the starter out so you can look in there.
But really these engines don't have a lot of oil leaking problems and more than one owner has experienced rear main seal failure. Add to that two shops have already diagnosed it as such. That's two opinions from direct inspection, not an unknown failure mode for this application, and you said yourself that 4 tablespoons worth of oil came from inside the bell housing from the fording plug....... not only does it look like a duck and quack like a duck - it smells like one too.
But do the UV test after cleaning - pull starter and use half a case of brake cleaner through every orifice and get your inspection camera ready.
Ronmar
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I could see flung oil inside the bell-housing weeping thru the joint between engine and bell-housing and bell-housing and transmission, but I don’t see it being flung beyond that as the bell-housing is not under pressure. After it weeps, its down or wherever it is blown by the wind tunnel up front. I surely don’t see how it would make it out and across the river of air and onto the ex brake actuator…
I also think if it was a rear main, once you pulled that drain plug it would be your new prime oil source... now how those 4 spoonfuls of oil got in there is a question that needs answered. You may have more than one leak…
I think your source is forward along the passenger side. Could be turbo supply or return, could be a turbo shaft seal dripping off the compressor housing. Could be from up by the oil cooler? Something dripping there could be blown to the rear into the areas you are finding oil. You could pull the turbo outlet pipe and see if there is any oil in there…
As mentioned, clean it all off throughly and start looking… a dry white paper towel can be handy for this, wipe, look, repeat all over all the parts.
I don't think the 3126 has any ports on the top rear of the block. Like the 3116 I think the only fitting on the rear is the fuel line from the fuel gallery in the head, to the pressure regulator and back to the tank return.
I also think if it was a rear main, once you pulled that drain plug it would be your new prime oil source... now how those 4 spoonfuls of oil got in there is a question that needs answered. You may have more than one leak…
I think your source is forward along the passenger side. Could be turbo supply or return, could be a turbo shaft seal dripping off the compressor housing. Could be from up by the oil cooler? Something dripping there could be blown to the rear into the areas you are finding oil. You could pull the turbo outlet pipe and see if there is any oil in there…
As mentioned, clean it all off throughly and start looking… a dry white paper towel can be handy for this, wipe, look, repeat all over all the parts.
I don't think the 3126 has any ports on the top rear of the block. Like the 3116 I think the only fitting on the rear is the fuel line from the fuel gallery in the head, to the pressure regulator and back to the tank return.
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Pulled the starter. Seems someone was messing with it at some point because it was pretty loose and one of the bolts was broken. Hiding behind the starter is a nice block crack..... So this seems to be the slow leak source. Mechanic is pretty sure its a weldable crack. This is why it looked like the oil was coming from the starter even though there is no oil connections there. I do also need a new starter. Does anyone have a good source for a 3126 starter?
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Btw.. to replace a $50 rear main seal is $3k-$4k
Ronmar
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Yup, less if you have your own big tools and talents...
Yes. 3200 is right but they pull it so the block can be welded, change the RMS and a few other odds and ends. But I’m already into the truck for some $ so what’s some more $ now to make sure it’s good and doesn’t spew oil.