oil dripping from backside of LB7

'01 LB7, 285K miles
I'm noticing oil spots on my driveway. A quick look reveals oil droplets hanging from the bolts which hold the oil pan from underneith. Without putting the truck up on a lift and doing an inspection, my "guess" is that I've got a leaky gasket. I snugged the bolts on the back of the oil pan but that didn't suppress the leak (not surprised). I recently changed the oil after having the injectors replaced. I smell no fuel in the oil when dipping my finger into the drops- smells like engine oil!

I sounds like this oil pan is a 2 piece deal. Any guess as to what it might be from? I'm guessing that, since the oil is on the pan bolts, it's not the rear main seal of the crank. I'll find out more after I take it in to the stealership and have them look at it.

An oil leak in the area you mentioned is not likely to be due a poor sealing oil pan or aluminum crankcase. Could be, but not likely. Be careful tightening the oil pan bolts - they're small and they thread into aluminum, and the threads are easily stripped or cross-threaded if removed and reinstalled. Other than RTV, there is no gasket in these areas.

Oil filter adapter?

Jim

Local dealership says they can't find a leak, but did mention that the pan bolts were able to be turned "a bit". I did this a couple of days ago and it still leaked. Any thoughts on the rear main seal starting to let go?

As More Power said, much more likely the oil filter adapter. Also, a sloppy oil fill can allow oil to run across the top of the engine, and dump out the back, above where you described. If it is the rear main, check your crankcase vent. A blocked or damaged vent almost always leads to seal leakage (positive crankcase pressure). With high mileage, the vent filter may be oil-soaked or otherwise blocked. While the engine is running, it should "pulse/puff" a little air. Also check the vent caps on the valve covers (small square covers on the valve covers).

Quote:

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Originally Posted by chessy56

Local dealership says they can't find a leak, but did mention that the pan bolts were able to be turned "a bit". I did this a couple of days ago and it still leaked. Any thoughts on the rear main seal starting to let go?

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Chessy56,

I apologize for you concern. If you would like I can call the dealership to see if there is another alternative for your concern. Please PM me your first and last name, address, phone, VIN, current miles and dealer.

Please feel free to let me know any questions, comments or concerns.

Thank you,

Tina
GM Customer Service

A couple of more things that may help resolve this post:
I've been reading on the PCV system- I saw the 2 square PCV valves on the valve covers and the hoses run to a "T"- the 3rd hose runs to a canister which is mounted to the right side of the engine, next to the belt tensioner. Is this the 3rd PCV valve? If so, it's still the original and has never been replaced/serviced after 285K miles. Is this a replaceable item?

If oil was dripping from the filter adapter I'm certain I or the dealership would have seen this. Hard to imagine both of us missing that one. When I fill with oil, I use a "large" funnel in the oil fill neck- no spillage there.

Judging by the hose that runs from the bottom of this canister to some point below, can I assume this is the reason my oil pan is always wet with oil near the front of the engine? (I've never had to add oil between oil or filter changes; just an observation I've made). Maybe my crankcase is getting pressurized and oil is being forced out past the pan sealing surface or the rear main. If it's leaking out the rear main, why would my pan bolts have oil hanging from them, but the bell housing immediately next to the engine block doesn't appear to be just as oily?

Does a CDR valve have anything to do with this (or, is the CDR the same thing as the PCV on a diesel)? I'm still learning after 11 years with this truck and my preference is to keep it for a while yet. Comments welcome.

It doesn't have a CDR or PCV. The crankcase vents to atmosphere (through the pipe below the canister). The canister is just a filter, to capture oil vapor/droplets, prevent contaminants from entering the engine, and muffles crankcase vent noise. If your pan is damp with oil around the end of the vent area, it's the problem. Over time, the filter (canister) gets dust/soot/oil-soaked, and passes liquid oil. You can clean it (back-flush it in a solvent tank, or poor gasoline/kerosene through it, blow dry with shop air), or replace it.

Just FYI, a CDR or PCV is a valve between the crankcase and intake, designed to prevent excessive vacuum on the crankcase. CDR for Diesel, PCV for gassers. Essentially the same things. Engines that vent to atmosphere don't have "valves" or "regulators", only filters (aka: muffler, silencer, or damper).

dealership added a dye to the oil- no apparent signs of oil leakage. Diesel fuel can be smelled. After pulling a couple of things from the top side of the engine, I could see a small reflection of (diesel) atop the intake manafold- it must have been running down the valley and the backside of the engine if parked with the nose uphill. Plus, having the lift pump enhanced the problem. I didn't notice any more leaks once I deactivated the lift pump, but I could see that the hose leading to the injector pump was quite "wet". Dealership confirmed- hose replaced. Which leads to another question on hose routing, which I'll include in a new post. Thanks for the tips folks....