6.4 Rear Main Seal Question

[Skrap]

All

Got a question. Have a 2015 2500 with a 6.4. Has approx 63K miles on it. No issues really but on the last dealer oil change the service writer at the dealer said that the tech mentioned there is a small leak forming at the rear main seal. I'm not too worried as I Have the lifetime warranty. Here is my question.

I have about a 3200 mile round trip while towing a 24' cargo trailer that will weigh in the neighborhood of about 8-9K lbs. Is it imparative that i get this work done prior to my trip? Not getting done prior do i risk causing some major engine problems? Thanks in advance.

 

[RodeoRam]

Shouldn't be a problem if it is just starting. Keep an eye on the ground under the truck if you're parked and check your oil like you should be doing anyway. Have a couple of extra quarts of oil with you which you should have anyway, too.

Most rear main leaks are caused by the crank getting out of round with use over time. The crank ovals the seal a little bit letting oil by. Replacing the seal is a temporary solution that will happen again until the crank is replaced. On the other hand, it could be an actual seal problem which is why you should keep an eye on it. 63k seems a little too soon to me. I didn't replace my rear seal on my 2001 5.9L until 200k when Aamco serviced the transmission.

 

[chri5k]

Shouldn't be a problem if it is just starting. Keep an eye on the ground under the truck if you're parked and check your oil like you should be doing anyway. Have a couple of extra quarts of oil with you which you should have anyway, too.

Most rear main leaks are caused by the crank getting out of round with use over time. The crank ovals the seal a little bit letting oil by. Replacing the seal is a temporary solution that will happen again until the crank is replaced. On the other hand, it could be an actual seal problem which is why you should keep an eye on it. 63k seems a little too soon to me. I didn't replace my rear seal on my 2001 5.9L until 200k when Aamco serviced the transmission.

Can you explain how a hardened steel crankshaft gets "out of round" ?

 

[RedSRT4Me]

Can you explain how a hardened steel crankshaft gets "out of round" ?

Usually one of the main bearing caps developed a tiny .0001 leak or out of round.

Your question seems more like you don't believe the answer so I'll apologize now for not going into great detail, but crankshafts do have this problem over time.

Sometimes it's a crankshaft manufacturing defect. Could be the assembler was coming in on a Monday and forgot. Someone put tons of boost creating massive cyl pressure etc.

I'll edit this post instead:
Don't read this like it's a common problem. It was to answer your skepticism that's all.

 

[RedSRT4Me]

Here is a better answer than I could give in my own words

The rear main seal is installed between the rear main journal and the flywheel. It is commonly a synthetic rubber lip-seal. The seal is pressed into a recess between the engine block and the oil pan. The seal has a shaped lip which is held tight against the crankshaft by a spring called a garter spring.

A failed oil seal is a major problem because they are adjacent to main journals which receive, and need, a good supply of pressurised oil. Combined with the spinning of the crankshaft, this leads to rapid loss of engine oil through any breach of an oil seal.

 

[chri5k]

Usually one of the main bearing caps developed a tiny .0001 leak or out of round.

Your question seems more like you don't believe the answer so I'll apologize now for not going into great detail, but crankshafts do have this problem over time.

Sometimes it's a crankshaft manufacturing defect. Could be the assembler was coming in on a Monday and forgot. Someone put tons of boost creating massive cyl pressure etc.

Not sure how a 0.0001" "leak" in a bearing with a specification for clearance of 0.0009 - 0.002" is even a leak much less cause the rear main seal to fail. I could see a garter spring failing / stretched / losing tension or hardening of the rubber seal lip causing a leak as plausible but not some nebulous out of round condition just happening. I did probably 40 crankshafts for Chuck Downs of Bob Penske racing and never saw anything like you are describing happening to crankshaft in a racing engine that went 500 or more laps.

 

[yoda]

Cant say I've ever had a crankshaft out of round causing a rear seal to leak. Crank thrust bearing wear, causing excessive crank end play a few times.
Very, very unlikely, probably just a failed seal.
If that's even the source of the leak. Rear main seals are often misdiagnosed. Just because that's where the ends up doesn't mean that's what's leaking

 

[Burla]

Seams like every manu has a tolerance for rear main seal leakage, it is very rare they would replace the seal just because of a drip, because it is such a large job. In the 90's I was told my rear main couldn't be replaced because it wasn't leaking enough and back then it was 600 to fix, I can only imagine what it would cost today to fix that. And that time it was their fault, they fixed my transmission and used the old seal like a dummy. I couldnt really complain because they did me a favor and fixed trans under warranty even though I was out of warranty, but I would be surprised if any dealer or manu would fix a main seal for a drip. I drove that truck for 8 years with a leaky seal before I sold it, never an issue.

 

[RedSRT4Me]

Not sure how a 0.0001" "leak" in a bearing with a specification for clearance of 0.0009 - 0.002" is even a leak much less cause the rear main seal to fail. I could see a garter spring failing / stretched / losing tension or hardening of the rubber seal lip causing a leak as plausible but not some nebulous out of round condition just happening. I did probably 40 crankshafts for Chuck Downs of Bob Penske racing and never saw anything like you are describing happening to crankshaft in a racing engine that went 500 or more laps.

It was an example that racing engines would never see. Racing engines are torn down and rebuilt repeatedly.

 

[RedSRT4Me]

All

Got a question. Have a 2015 2500 with a 6.4. Has approx 63K miles on it. No issues really but on the last dealer oil change the service writer at the dealer said that the tech mentioned there is a small leak forming at the rear main seal. I'm not too worried as I Have the lifetime warranty. Here is my question.

I have about a 3200 mile round trip while towing a 24' cargo trailer that will weigh in the neighborhood of about 8-9K lbs. Is it imparative that i get this work done prior to my trip? Not getting done prior do i risk causing some major engine problems? Thanks in advance.

There really is only one way to find out about the trailer haul. Just use your best judgement. At some point if you ever need an engine rebuild make sure they check all clearances. The crank can always be turned to make it true again. Just need new bearings depending on how much material was removed.