Oil leak crankshaft?

[Pogust]

1996 6,5 TD in a motorhome, done only 40 000 km, most of them the last 2 years. Started to leak motor oil from rear of engine last summer, looks like it comes from crankshaft rear seal. Not much oil coming yet, but it gets messy under the rig all the way back. Been degreasing and washing under to try find leak.

From what I understand I would have to take gearbox down to replace the seal? Not something I feel like doing at the moment. Haven't taken the cross exhaust pipe down and the flywheel cover yet to look better. What is your experienced suggestions? Can it be something else than the crank seal?

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P-O

[Robyn]

Hard to say for sure without getting the can off the flywheel housing.

These engines use a one piece crank seal, that is pressed into the block.

Even with the tranny back out of the way, you need a tool to remove and replace the old one.

With the flywheel cover off, you can see up in there pretty good, and should be able to determine the source of the oil.


Good luck

Missy

[Big Green]

Check the rear corners of the valve covers before starting any major surgery

Big Green

[Robyn]

Good idea.

These can start leaking and drizzle down and actually end up looking like a lower end leak.

Once oil gets down under, the wind blast coming back will spread the oil to the point that its tough to say where its coming from.


Missy

[Pogust]

Thanks Guys,

Went looking under the hood, clean and dry around the top. Yes the wind is the problem, hard to say where it originate. Soooo, guess I have to take cover off the flywheel then. And have another go with degreaser before starting up and let her idle for a while.

I wonder, could I put diaper on her... Some sponge tied up between the engine and box that could be squeezed clean of oil once in a while.. :D Can't be much of a leak (yet?) and I don't do that many km a year in it.

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P-O

[rustyk]

Also check the oil drain lines on the turbo - I suspected a front seal leak on mine (pusher), but the turbo drain was seeping. In a puller, the oil might run along the pan flange and make it appear there was a leaky main seal.

[Pogust]

Degreased engine, ran it for an hour without any sign of oil. So no answer yet where it comes from :confused:. Will have to wait until I go for a longer tour and try find the leak then. Off to the north cape of Europe next month :)

Anyone with experience with oil additives that swell seals? 17 year old engine that been sitting in a shed most of the time and only done 40.000 km could have hard rubber seals that might work better with some softening up... Or...
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P-O

[phantom309]

I,d check the oil filter adapter housing to block,.
famous for leaking, then looks like a rear main,.

jmho

Nick

[Yukon6.2]

Hi
It may be coming from the valley drain,it dumps out the back of the motor.
Some have a pipe that brings it out of the bellhousing,and some don't.
Thomas

[Warren96]

Since your question was "Can it be anything else?" let me offer my problem I had with my 6.5. A leakey fuel heater on mine caused it to leak under the truck in this exact same spot, and like you said it gets everywhere.

[racer55]

Might also want to service or replace the CDR valve.Some parts places refer to it as a PCV valve incorrectly but it will still get you the correct part in most cases.

It's purpose is to try and maintain a slight vacuum in the crankcase and when they don't work properly can contribute to oil leaks that are encouraged by crankcase pressure.

[DmaxMaverick]

It's purpose [CDR] is to try and maintain a slight vacuum in the crankcase and when they don't work properly can contribute to oil leaks that are encouraged by crankcase pressure.

This is a myth. The CDR (Crankcase Depression Regulator) prevents excessive crankcase vacuum, which can defeat seals and allow contaminants INTO the engine, and cause increased oil usage due to oil vapor scavenging. The valve is normally open, and progressively closes as intake suction increases due to several factors, including engine RPM and air filter element condition. When they fail, they won't cause external engine oil leaks. The 6.2/6.5L engines run fine with near zero crankcase pressure, and many of them have been modified with the vent to atmosphere. Incidentally, the LB7 Duramax engine is vented to atmosphere (except 02-04 CA). It's the EPA that required the closed-circuit system. A PCV (Positive Crankcase Ventilation) regulates crankcase pressure to a slight vacuum, essentially a polar opposite to Diesel engine operation.

Positive crank case pressure is caused by excessive blow-by, more than can be scavenged through the crankcase vent, regardless of CDR operation. If the main seals are leaking, either the seals are completely shot (weeping residual oil after shutdown), or the engine is producing excessive blow-by, defeating the seals AND the CDR.

[Pogust]

Just an update if someone reads this thread later with similar problem. I done 12.000 km around Europe this summer without any leak. Not a drop of oil under the motorhome. To me it seems the engine was sitting too long unused and crank seal got too hard. When using vehicle again it softened up by itself and is now working OK.

Thank you for your suggestions anyway, they may come handy another time...

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P-O