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Discussion Starter · #1 ·
I’ve got an 07 5.9 with g56 6 speed just bought off a guy said he had dye put in an checked an was oil plan leaking, so he says. I Drove a few days and it had enough oil leaking to be going up the tailgate the second day I had a bit of fire wood in the back an a light 16 ft trailer with a two bottom plow an field cultivator, so no real weight on, went about 50 miles an blew out about a half gallon of oil an covered the trailer, back of truck an even had it slung up the ds front an rear doors an bed side. Degreased everything an power washed an put up on rack thinking it would be pretty clear what was leaking. Ran ten minutes 5-8 of that was at 2000 rpm an got to temp but never had a drop of oil show up anywhere. Yes it still had oil in it to leak out. Any suggestions? Thanks
 

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Sounds like the oil leak manifests when the engine is under load / increased boost pressure. Check the crankcase vent to see if it's plugged. That does not answer where the leak is coming from, but it may help your situation.

There was a post not too long ago about another (I believe) 3rd gen experiencing the same problem. Massive oil, then it mysteriously went away. I don't believe a cause or leak source was ever found.
 

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Over filled maybe?
 

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Rear main seal would be my guess. I had a very similar leak with the same conditions on my '06. (i.e. oil all under the truck, up the tailgate and on anything I towed)

To pin point the leak, (it presented itself as either the rear main or oil pan) I had the underside of the truck cleaned, removed the inspection cover from the trans bell housing and drove it a bit then let it sit. A puddle developed directly under where the trans inspection cover would have been and was dripping off the back side of the block.

One other thing I did to eliminate blow by out of the slobber tube was I put a water bottle as a catch can on the end of the tube, drove it and checked to see if it was collecting oil. There will be some but it should not collect to the point there is liquid in the bottle. Also, make sure the bottle has a hole in near the top of it for a vent since the slobber tube is about the same diameter as a standard water bottle neck.
 
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Does the oil smell like diesel? I had something very similar happened, truck would blow oil/diesel out the blow buy tube and soak the underneath of the truck. It also got on the tail gate . Turns out I had a crack injector or two filling my crack case . It also damaged my turbo .

when the truck was up to temp the diesel would boil off and smell awful. Like Sulfur and rotten eggs . It would also blow out diesel/steam out the blow-buy tube .


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Discussion Starter · #6 ·
Sounds like the oil leak manifests when the engine is under load / increased boost pressure. Check the crankcase vent to see if it's plugged. That does not answer where the leak is coming from, but it may help your situation.

There was a post not too long ago about another (I believe) 3rd gen experiencing the same problem. Massive oil, then it mysteriously went away. I don't believe a cause or leak source was ever found.
Sounds like the oil leak manifests when the engine is under load / increased boost pressure. Check the crankcase vent to see if it's plugged. That does not answer where the leak is coming from, but it may help your situation.

There was a post not too long ago about another (I believe) 3rd gen experiencing the same problem. Massive oil, then it mysteriously went away. I don't believe a cause or leak source was ever found.
yea I’m preemtty sure I seen that post an didn’t see where any problems or fix was found

Over filled maybe?
nope

Rear main seal would be my guess. I had a very similar leak with the same conditions on my '06. (i.e. oil all under the truck, up the tailgate and on anything I towed)

To pin point the leak, (it presented itself as either the rear main or oil pan) I had the underside of the truck cleaned, removed the inspection cover from the trans bell housing and drove it a bit then let it sit. A puddle developed directly under where the trans inspection cover would have been and was dripping off the back side of the block.

One other thing I did to eliminate blow by out of the slobber tube was I put a water bottle as a catch can on the end of the tube, drove it and checked to see if it was collecting oil. There will be some but it should not collect to the point there is liquid in the bottle. Also, make sure the bottle has a hole in near the top of it for a vent since the slobber tube is about the same diameter as a standard water bottle neck.
Have nothing coiming from their after cleaning it a and thought about the bottle truck today at work an going to give it a try thanks

Does the oil smell like diesel? I had something very similar happened, truck would blow oil/diesel out the blow buy tube and soak the underneath of the truck. It also got on the tail gate . Turns out I had a crack injector or two filling my crack case . It also damaged my turbo .

when the truck was up to temp the diesel would boil off and smell awful. Like Sulfur and rotten eggs . It would also blow out diesel/steam out the blow-buy tube .


Sent from my iPhone using Tapatalk
nope smell like oil no fuel thanks for the suggestion

So if it were the rear main as I first suspected and It leaks as much as it dose wouldn’t it be on covering the fly wheel an possibly make the clutch slip
 

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I’ve never worked on a g56 truck before but I assume there’s an inspection plate like the autos you can pull off and inspect the flywheel for oil?

I have the valve cover rocker box seal let loose in west Texas, covered the bottom of the truck and tailgate in oil by the time I stopped in Tucson and noticed. Only lost about a quart but it made a hell of a mess at highway speed. It was a little hard to tell at first where it was coming from but eventually reached behind there and the back of the engine was wet.

Once it’s hot I’d pull off the oil fill cap and see if she has bad blow by at idle. Should be able to set the cap on the hole and not blow off.
 

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Discussion Starter · #8 ·
I’ve never worked on a g56 truck before but I assume there’s an inspection plate like the autos you can pull off and inspect the flywheel for oil?

I have the valve cover rocker box seal let loose in west Texas, covered the bottom of the truck and tailgate in oil by the time I stopped in Tucson and noticed. Only lost about a quart but it made a hell of a mess at highway speed. It was a little hard to tell at first where it was coming from but eventually reached behind there and the back of the engine was wet.

Once it’s hot I’d pull off the oil fill cap and see if she has bad blow by at idle. Should be able to set the cap on the hole and not blow off.
I’ve never worked on a g56 truck before but I assume there’s an inspection plate like the autos you can pull off and inspect the flywheel for oil?

I have the valve cover rocker box seal let loose in west Texas, covered the bottom of the truck and tailgate in oil by the time I stopped in Tucson and noticed. Only lost about a quart but it made a hell of a mess at highway speed. It was a little hard to tell at first where it was coming from but eventually reached behind there and the back of the engine was wet.

Once it’s hot I’d pull off the oil fill cap and see if she has bad blow by at idle. Should be able to set the cap on the hole and not blow off.
no inspection plate that I see but their is a small slot in bottom of housing an adapter plate that you can see fly wheel edge an it’s dry. Cap stays over hole with the exception of vibrating back from beingdirectly over the hole
 

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Check the rocker box gasket. They are notorious for leaking and when they get bad enough resemble a rear main seal.
 
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I'll say it again in case it was missed, make sure your crankcase breather is clean and unobstructed. Won't fix your leak, but can only help your situation.
 

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Just went through this nearly same issue...I put a post up on it a little while ago....there's an inspection cover on the G56 adapter plate behind and below the turbo on the stock turbo configuration...if you're getting oil inside the bellhousing, there's only one place it can intrude....rear main seal...you don't' say how many miles are on the truck?

Has the trans been removed? The adapter plate for the trans, that bolts to the back of the block also has an O-ring that seals the back of the camshaft, high on the Driver's side....if it's got more than 150K on it, there's a solid chance it's leaking there....it will run down between the adapter plate and look like an oil pan leak....I couldn't get mine to seal there for the life of me after I did my engine build, so the O-ring came out and a 1/4 inch bead of Ultra-Grey replaced it....

My rear main leaked zero at idle, or sitting in the driveway at 2000+ RPM's for over 20 minutes....I had to take it on an empty stretch of road and hammer it for several WOT acceleration pulls and then get under it with a flashlight...above the pan rail, (there's an indent in the back of the pan) between the engine and adapter plate, in the center you'll see an aluminum piece...if oil is showing there, it's a good chance it's a rear main seal....nearly all rear main leaks will show up in the window at 6 o'clock between the plate and the trans where you can see the flywheel....even after dumping 7 quarts over 2100 miles, my flywheel teeth looked dry, but if I pulled the inspection cover and looked in, I could see the shine of oil...as I said, that's' the only way oil can get inside the bellhousing, the rest of the engine is quarantined from the bellhousing.

Look closely through the driver's inner fender at the split between the trans adapter and engine with a bright light...if you see wetting in the gap, there's a solid chance it's leaking at the cam O-ring.

Let the engine cool and lay across the valve cover and reach your hand down the back of the valve cover on the back of the engine by the firewall....if it's the valve cover gasket, you'll have oil on the back of the head, below the valve cover...

I'd start at the top with the valve cover and move down....
 
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Broken ring/s failing piston on one or more holes.
Combustion gases blowing into crankcase overpressuring and blowing oil out blowby tube.
Too common failure in the Gen 3s.
Caused by failed leaking injector.
Run manometer test or put catch bottle and blowby tube to measure blown out oil.
Expensive repair
 

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Discussion Starter · #13 ·
So here is an update. After putting a bottle on the blow by tube an running the truck down the road I had some oil in the bottle but it was not blown into the bottle just run in to it on the outside of the blow by tube. Further inspection found oil coming from higher up an it was wettest around the clamp on the tube up on the side of the block. Thought maybe the tube was blocked some an had a crack in it up by the clamp so proceeded to remove it an check. In the process of removing the blow by tube noticed that the dip stick tube was rubbing the bolt that held clamp for blow by tube. Got tube out an had no issues, both ends of it were oily but it was a dry sticky oil an the outside of the tube was soaking wet. So went back in deeper an checked dipstick tube, low an behold it had two holes in it from where their is supposed to be a bracket spot welded to hold dipstick tube in place on the Same bolt that hold blow bye tube clamp. So previous owner or owners done something where they removed the clamp an bolt an the bracket got broke off the dipstick, they put it back together an probably said **** we messed something up better sell it. Lol so long story short my massive oil leak was from two holes in the dipstick tube. Fixed with a few welds! On to new problems with the power steering pulley bit I’ll make a new post for that
 

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now that its fixed and you have regained confidence in it, swap in 1 qt of stiction eliminator in the crank and run a quart of the atf/2 stroke oil mix thru it. then clean or replace the breather vent box.

the SE will clean the inside of the motor and the mix will clean the injection system.

then go do a valve adjustment on it.

then consider replacing all of the remaining fluids if you havent already... i do mine every 50k, all of them except the clutch system.
 

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swap in 1 qt of stiction eliminator in the crank

the SE will clean the inside of the motor
Did an oil change a couple weeks ago and did just this
 

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Did an oil change a couple weeks ago and did just this
notice any change?

iirc besides reducing the oil lose there was a slight bump in performance presumably because the rings were freed up to seal better against the cylinder wall. with the exception of tires that are approaching 90k on them, would not hesitate to head out on a long trip tomorrow with the 463k that is on it.
 

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notice any change?

iirc besides reducing the oil lose there was a slight bump in performance presumably because the rings were freed up to seal better against the cylinder wall. with the exception of tires that are approaching 90k on them, would not hesitate to head out on a long trip tomorrow with the 463k that is on it.
Not anything super noticeable, maybe the powerband is a tad more smooth if that makes sense? Then there's the awful smell.

I didn't really have any reason to try it as my rig is running fine, I figured with almost 290k on the clock and minimal towing it might be a good thing to give a go.
 
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Discussion Starter · #19 ·
now that its fixed and you have regained confidence in it, swap in 1 qt of stiction eliminator in the crank and run a quart of the atf/2 stroke oil mix thru it. then clean or replace the breather vent box.

the SE will clean the inside of the motor and the mix will clean the injection system.

then go do a valve adjustment on it.

then consider replacing all of the remaining fluids if you havent already... i do mine every 50k, all of them except the clutch system.
Correct me if I’m wrong but on 06-07 I thought the ccv was made into the valve cover an the only way to replace it was to replace the whole cover.
 

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Correct me if I’m wrong but on 06-07 I thought the ccv was made into the valve cover an the only way to replace it was to replace the whole cover.
that is what i hear, doesnt mean it cant be cleaned... would just need to figure out how.
 
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