Oil Leak That Seems To Defy Logic

[burnoil]

On my '84 K30, 6.2L, Banks, I have an oil leak. Ok, several oil leaks. I think every gastket (or sealing area) is leaking--some more than others. This is where my problem is. My oil pan and timing cover are leaking a fair bit--quite moist, but no real "flow" off of them. My valve covers have some seepage with a thin film of coagulated funk around them, but I don't think I would classify them as even being moist--very minimal leakage. Same with the vacuum pump mounting area. No oil cooler line leaks, turbo oil feed line is cool and fuel pump mounting area is dry (I guess not all the gaskets are leaking....)

Here is my problem: NONE of these leaks/seeps combined are enough to explain the quite severe river of oil I have coming down the back of my block on the passenger side. That may be an over-dramatization of the leak, but it is a doozie. I put a couple bottles of Fluoro-Dye in it to try to nail down the origins. It did not help because the product is junk. I don't recommend it to anybody. Then I installed a couple ounces of Tracer Line dye. Holy cow!! I found leaks in areas I didn't know I had leaks. That stuff is fantastic and carries my full recommendation for fluid dye. Anyways I found a VERY bright line of dye down the head gasket on the valley side of the head. I found no dye above the line at all (not coming from valve cover). The area in and around the intake runners is dye-free. The parting line/head gasket line is quite clean but the area immediately surrounding it is very damp coagulated funk indicating that the oil is flowing out the head gasket area keeping it clean and coagulating around the area. Looking up at the back of the motor, there is dye residue about 1/2" up form the head gasket line (wicking up/wind blown??) with no dye present around the valve cover. My starter glows like a night light with all the dye on it as does my front driveshaft, transmission, transfer case, et al.

Harkening back to my gasser days on Chev motors, I know it is almost impossible to get an oil leak from the head gasket and I am ASSUMING that this is also the case with the 6.2L. Does anyone have an idea or previous experience or even ever heard of this before?? I debated quite awhile before making this post because it *shouldn't* be possible, but I can not find any other source of the flow. The motor runs tip-top. Immediate startup with smooth running characteristics. I have no reason to suspect a compression leak from the gaskets--just oil.

[Robyn]

Howdy

I have chased oil leaks down on these engines many times.
Be very sure your CDR system is working to keep a slight vacuum in the crankcase.

The head gaskets rarely leak oil. Have you checked the gasket on the oil pump drive?

Even though the oil does not seem to come from the VC I am betting this is the culprit.

There is very little else up top that can leak.

Be sure you dont have a leak at the IP thats flowing down under the manifold and out the back.
The oil pressure sender can also leak but both the sender and any oil coming down the valley usually lands on the other side of the engine.

These engines can get a tad sloppy after many miles.
If you redo the VC be sure to get the covers nice and flat and clean all surfaces very well with Brake Kleen or similar oil disolving chemical that leaves things dry.
Use a good high temp silicone sealer on the covers and goo them well.
Over tightening the bolts can cause all sorts of grief.

If your CDR is not working right, with the Turbo huffing away the crankcase can become pressurized and this will really make them leak.

Slight negative is the key here (couple inches of water column)


Good luck

Robyn

[burnoil]

Thanks Robyn.
Can I hook a vac gauge to the dipstick to check it or is there a better way to check the CDR??
Is it best to do with the motor at full operating temp or does it matter??

As far as other leaks go, the oil pump drive is dry--some seepage, but no dye visible and the same goes for the IP. The valley is dry. The only wet oil and dye is along the "ledge" right below the cylinder head mounting surface.

[Robyn]

Warm engine, use a gauge designed to read in inches of water column, "NOT" inches of mercury. The spec on this should be in the GM service book but operating on the road a reading of 0-3 inches would be my guess. The idea was to keep a slight negative pressure in the bottom end to stop oil leaks.

Looks like the only real choices are the VC and the heads. My best guess without seeing it is VC as these are notorious for leaks when they get time on them.

The wind/air flow can mess with the stuff and confuse the issue some. The choices are limited. You have ruled out the IP, Pump Drive, and such so really the only other choices are the VC or the head.
I have not seen any head gaskets leak that much oil. The area of gasket along there is pretty good and there is nothing really to cause a failure.

Unfortunately the Injector lines have to come off to get at the VC.

Pretty much gonna have to rip it open and see.

The oil will leak from the VC most when the engine is worked at speed as the amount of oil in the top end is higher due to the throw off from the rockers. The chamber drains well but at speed there is a lot of oil flying around under the covers and if the seal between the head and the cover is compromised it will leak.

As a test you can try cleaning the area very very well with something like brake Kleen
and smearing high temp silicone sealer along the part line of the VC and the head. let it sit over night and then try it. If the leak stops your on it.
This is obviously not a permanent fix but can be useful to diagnose the issue rather than ripping off the lines and the cover .

Good luck

Robyn