OIL LEAK

[john robertson]

My motor has about 6000 miles on it and I have developed an oil leak. It doesn't leak while idling or sitting over night. It leaks while driving. It's dripping on the crossover pipe, my deep trans pan gets wet, and the floor, mainly on the driver side gets wet and there are drips hanging from my rear transmission support, and wet behind it and back to the mufflers. I guess my question is can the oil blow out through the rear main seal, but that seal not leak while not running or idling? I'm asking because I've checked the usual places, valve covers, rear of intake, oil pan, front stuff, etc. Could I be pressurizing the crankcase with boost, and causing the rear main seal to allow oil to blow by? I'm going to bypass the PVC tomorrow and see if that helps. I had a shim on my stock oil pump relief spring to increase oil pressure which I removed today. Still leaked on 10 mile cruise. I'm running my oil level a pint over full which I'm going to remove tomorrow. However, I've run it this way for 6000 miles with no issues. I would go ahead and replace the rear main seal and oil pan gasket, but I hate to do all that and have the same problem. Any speculations or suggestions would be welcome. 

[Steve Wood]

I would start by checking the pcv for proper operation. If it is not working correctly, you can pressurize the lower end very quickly.

  Might not be a bad idea to clean it off around the rear seal as best you can and then check it after a short drive to see if it is wet immediately around that area.

Also check the rear of your intake and see if it is leaking between the intake and the block...that used to be a common problem.

Running a pint over full may not be a good idea but that does not sound like the problem at the moment

[earlbrown]

The overfill rule is for the transmission.   Overfilling the oil is a good way to have an aerated frothy mess going through the bearings instead of oil.



For the leak itself, leave the torque converter cover off and brake parts the hell out of everything.  Once you know everything is dry dry dry, go for a SHORT drive then throw some baby powder on the bottom of the engine.   Any moistness will light up like the 4th of July.

[john robertson]

I'll be checking the PCV situation today, and will again jack up the car and check out the usual suspects. Also, I don't run a torque converter cover, and basically, the torque converter is not wet, but there is aways fresh oil on the crossover pipe on the left side of it. Can it be blowing out the rear main seal, but not dripping on my driveway at idle?

[Steve Wood]

It really does not sound like a main seal leak unless the crankcase is pressurized while driving and it should not be.  If the engine has a lot of blowby which you would probably see at idle with smoke coming out the valve cover oil filler hole-I think.

Or, perhaps, if the engine was worked on, an oil passage hole by the back of the cam may not have been sealed properly.

[john robertson]

OK, I plugged the PCV and took it out, and found it was dripping pretty good, even at idle. I brought it home, jacked it up, let it idle and found it's leaking out the base of the oil dipstick. It's no longer over full, but right at full on the dipstick. I'm going to pull the dipstick ou, check it out, and re-seat it and try to seal it. I have an O-ring on it, but it sits about a eighth or quarter inch above the hole, instead of being right down on it, though I don't understand why it's pushing oil out of it anyway. For more information, the motor runs strong; has relatively few miles on it, and it doesn't smoke, and certainly not out the breathers on each valve cover. 

[Steve Wood]

I had trouble with replacement dipstick tubes not seating, but not originals....i t has to compress that o-ring a bit.  Hopefully the tube is not cracked.

[john robertson]

Boy is it easy to fix an oil leak when you find where it's coming from.  Removing the PCV from the system increased crankcase pressure and allowed it to leak so I could watch it dribble out of the dipstick tube. When the leak was prevalent only in wetness on the oil pan and beyond, and leaking only while driving, by the time I looked for the source of the leak, the area around and below the dipstick tube, which I did check, was not wet at all. Apparently at some point in the last couple months, the dipstick tube vibrated it's way up and out and allowed it to leak. It is a factory unit, but just slides in without any effort. In addition to seating it all the way down to the O-Ring I rolled some masking tape around that part of the tube to make a tight fit. Took it for a five mile loop and the crossover pipe and beyond are stone dry.

Thank you both Steve and Earl for your suggestions and help.

[Steve Wood]

it's nice when it turns out to be simple!

[earlbrown]

None of my dipstick tubes have ever had O-rings. Mine were always a press fit with a layer or sealing jizz on them.

[gusszgs]

None of my dipstick tubes have ever had O-rings. Mine were always a press fit with a layer or sealing jizz on them.

Sealing jizz.....😂😂
You kill me Earl

[john robertson]

None of my dipstick tubes have ever had O-rings. Mine were always a press fit with a layer or sealing jizz on them.

Well, in 22 years of owning these particular Buicks, big blocks before, I never needed any sealing jizz on the dipstick, so, who knew? Next time I have a leak, I'll just reach for the jizz.

[earlbrown]

I've found one can sometimes get in trouble for going in dry.