oil weeping out crankcase vent tube???

[boots]

re:2002 duramax 2500HD 4X4 crew cab LB

Last week I developed a radiator hose leak on the bottom hose....only had to add water once....just a split at the clamp...cut 1/2" off, clamped it back on, good to go....did that on Sunday evening....Monday, I noticed oil dripping out of the crankcase vent tube on the front of the engine on the passenger side and oil has blown out everwhere underneath and rear of truck..about a pint mabey...this truck has never leaked a drop of oil...as of today truck still reads no oil loss on stick but it is still leaking plenty...any ideas before I take it in to the dealer?...could I have knocked something loose that I am missing visually?....there is also a little bit of roughness at idle...the truck has 82000 mi. & gauges are reading normal...bad injector?? thanks, Boots

This is fairly common. Just oil vapor and nothing to worry about. The 2001 guys started the hose extension idea and I followed suit. Keeps the underside a bit cleaner...

boots,

As John said a little oil around the end of the LB7 vent tube is normal. However, a bad injector or leaking return line an cause the crankcase to fill with fuel. This can result in oil-fuel blowing out the vent tube and coating the underside of the truck. When this happens a drop in oil pressure is also noticed.

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Boots, If its an internal fuel leak your probably covered by the 200,000 mile warranty on the 02, I'd take it to the dealer with that in mind.

[DmaxMaverick]

Welcome to the forums, Boots.

Rough at idle?? Oil leaking from the CC vent?

Even if your oil pressure hasn't dropped, you could still have a significant amount of fuel in the oil. Just checking the dipstick like normal, you could be missing something. Fuel diluted oil can be "invisible" on the dipstick, only showing oil in the grooves, which one would see as normal. Check the level very closely on the dipstick. Look for "other than oil". As soon as you take the dipstick out, lay it on a white paper towel. The actual level will become evident as it soaks into the paper. If it "runs" across the paper, it is likely fuel. If there is fuel in the oil, there should be 2 distinct colors/consistencies on the paper.

The reason for the rough running connection is a crankcase full of fluid has very little or no air gap between the moving parts and the fluid. This causes much more resistance with the moving parts, namely the crank and pistons/rods.

Originally posted by DmaxMaverick:
............. The actual level will become evident as it soaks into the paper. If it "runs" across the paper, it is likely fuel. If there is fuel in the oil, there should be 2 distinct colors/consistencies on the paper............. [/QB]

I seem to have a problem grasping why/how diesel will separate itself when placed on paper. I'm experiencing lowering oil pressure myself. The 'rope' dipstick is no help if +. Works ok for lower than full. Did the paper thingy and noted nothing significant. Wouldn't the diesel be homogenized w/the CC oil? Afterall they're cousins and being whipped together by the crankshaft, bearings, passages etc Wouldn't it be a single element after a few miles?

[DmaxMaverick]

Originally posted by oyazi:
</font><blockquote>quote:</font><hr />Originally posted by DmaxMaverick:
............. The actual level will become evident as it soaks into the paper. If it "runs" across the paper, it is likely fuel. If there is fuel in the oil, there should be 2 distinct colors/consistencies on the paper.............

I seem to have a problem grasping why/how diesel will separate itself when placed on paper. I'm experiencing lowering oil pressure myself. The 'rope' dipstick is no help if +. Works ok for lower than full. Did the paper thingy and noted nothing significant. Wouldn't the diesel be homogenized w/the CC oil? Afterall they're cousins and being whipped together by the crankshaft, bearings, passages etc Wouldn't it be a single element after a few miles? [/QB]</font>[/QUOTE]The fuel will wick into the paper at a faster rate than the oil. Even if they are "homogenized", the heavier viscocity of the oil will wick slower. You can also use a coffee filter for a comparison. The fuel will separate from the oil enough to see it if the amount is significant enough, which isn't much. My fuel in oil issue was caught early on and didn't spew out, but was enough to cause a rough idle. The oil on the paper trick was obvious. Perhaps if you have run for several thousand miles with them mixed, it might be less evident. In most cases, the fuel will fill the crankcase rather quickly. In my case, 60 miles was more than enough. A full crankcase is about 5 gallons, which would make the ratio about 1:1, oil/fuel when it starts to blow out. I drained about 18 qts. from mine.

Try the paper trick for an idea what it looks like w/o the fuel contamination. Add a little fuel to the oil, mix it up real well, then try the test.

The reason for laying the dipstick on the paper initially is to determine the actual level. There will be more oil (or whatever is in the crankcase) at the actual level, than what gets wiped onto the dipstick as you pull it out. Oil contaminated with fuel can be invisible on the stick at a normal look.

I believe I'll make it a point to run 1/2 qrt low ~ then if it rises the full pip mark would make it obvious somethings amiss. Already done that w/the tranny ~ but its the eng oem dipstick that takes the cake.

Thanks for the response ~

There is a service bulletin on this, the oil drainback becomes clogged in the oil seperator and it runs out of breather pipe. The fix is a new check valve in the oil seperator, I think, if memory serves.

try this....

If an excessive oil leak from the PCV vent tube has been verified, check for diesel fuel in the oil.

If diesel fuel is found in the crankcase, complete the current SI diagnostics for Fuel Leaks Inside of Engine

If there is no fuel in the engine oil and the crankcase is not overfilled with oil, check for a sticking or inoperative PCV check valve. The procedure for checking the PCV check valve is found below.

Shut off the engine and wait five minutes to allow the decompression of the crank case. Remove the brass colored check valve at the base of PCV box which is a part of the alternator bracket. If a measurable amount of oil (more than a several drops) flows out of the PCV box replace the PCV check valve P/N 97302067. This is a one way check valve which should have a free flow toward the crank case when the engine is not running. Oil accumulated in the PCV box should flow freely into the crank case past this valve with the engine not running. When the engine is running crank case pressure may prevent oil in the PCV box from flowing into the crank case.