Rear Main Oil Seal Leak in Car? Need mechanics to weigh in!

General Questions
#1

Okay here is the story:

My wifes 97 Isuzu Rodeo had a rear main oil seal leak and a couple other gasket leaks. We take it in and got them “fixed”. A couple of days after that we noticed some small leaks (like the size of a quater or half dollar) on the cement. So we take it back in and the mechanic informs us that the PCV/PVC(?) valve he forgot to clean and was clogged and subsequently was then causing pressure and oil to squeeze out of our new gaskets that he just put in. So he cleans the valve and that seems to solve the problem with the little oil leaks.

THEN… about 5-6 months later our car is leaking oil like its going out of style. We are talking BAD oil leak. As in we had to bout 2.5 qts of oil in after the last oil change. We took it back to the guy and he says that what has happened is that the car NOW has an oil pan gasket leak. WHA!!! :eek: And he says its because the oil pressure is running high and this can cause gaskets to push out etc. even though our oil pressure gauge doesnt show a high pressure.

He also said that if we fixed this gasket and the pressures still ran high it could mean that we might need an engine rebuild - WHA?!?! :eek: All this over oil leaks.

So my father in-law says that the guy should have had to pull the oil pan and hence had to at least look at the gasket when he replaced the rear main oil seal leak and should have known it was bad at that time but he said it sounded kind of fishy to him.

We plan on taking it to someone else for a second opinion but what we are wondering from you car mechanics or ethusiasts out there is does this sound kind of fishy to you that this would be happening about 6 months after having the engine pulled to fix a rear main oil seal leak?

We would love your guesses, ideas, two cents and opinions - thanks!

#2

High oil pressure won’t cause the pan gasket to leak, but a clogged PCV valve might. The PCV valve is Positive Crankcase Ventilation, the PCV valve is basically a check valve. If it gets clogged, the pressure in the crankcase can get too high, causing oil leaks.

The guy probably had to pull the oil pan to change the rear main seal and didn’t put a new pan gasket in. Now it’s leaking. I bet a new pan gasket and a new PCV valve will fix you up. It should be a LOT cheaper to replace a pan gasket than a main seal, but the guy is feeding you BS about high oil pressure causing your leaks. IMHO.

#3

Frankly this guy does not sound like the sharpest knife in the drawer.
Oil pressure (high or low) is not going to destroy the oil pan gasket on your engine. Period. No discussion. End of story. The oil pan gasket seals the oil pan to the engine block it is not exposed to oil under pressure. I don’t know how much you know about engines, so let me try to explain.
The oil pan is the reservoir that holds the oil before it is pumped under pressure to the bearings. The oil pump picks up oil from the pan, pressurizes it and sends it through the oil filter, the through small passages to the crankshaft bearings, the camshaft bearings, and to the hydraulic lifters (If your engine has them) The oil that lubes the bearings, leaks off (somewhat and slowly at a controlled rate) and that oil drips back down into the oil pan to start the journey all over again.
Furthermore as the engine wears the clearance on the bearings increase. As the bearing increases the oil leaks past the bearings faster and the oil pressure goes down. I have never in 35+ years of working on cars heard of an engine where the oil pressure went up as the engine wore. It doesn’t work that way.
Get a second opinion. Due to the extreme amount of oil that has found it way out of the engine on your Isuzu Valdez it may be necessary for a shop to need to steam clean the engine, and/or add a UV tracer dye to the oil to determine the source of the leak.
As far as your father in laws comments, it may or may not be necessary to pull the pan to replace the rear main seal. On the cars I teach on, the pan stays in place, on other cars it must be removed. Maybe Gary T can stop by with a better idea on if pan removal is required on your engine.
Also it should not have been necessary to remove the engine to replace the rear main. Typically the transmission is removed instead. There are a few exceptions to this, Johnny LA’s MG being the one I am most familiar with.
As far as the timing goes, have you had an oil change recently? Oil filters have been known to leak, some times catastrophically. If the leak showed up right after an oil change, I would look at the filter and drain plug first. If nothing has been done recently, it could just be a coincidence. Shit does sometimes just happen.

[On preview] Yes a clogged PCV can cause a pan gasket to leak, but usually it cause the oil to push past the seals instead. Don’t forget the PCV was plugged after the first repair and it was pushing oil past the seals then. When the PCV was cleaned, the leaks stopped. I would not expect the PCV to get re-plugged in just 6 months but I guess it is possible. Again I would take the car to somebody else for a correct diagnosis.

#4

This is horsecrap. Engine oil pressure can be a factor in leaks of a pressurized component, like the oil filter housing or the oil sending unit, but it has no affect whatever on other gaskets and seals. Among those not affected by oil pressure are oil pan gaskets, valve cover gaskets, rear main seals, front crankshaft seals, and camshaft seals. If you understood him correctly, this clown has no idea what he’s talking about. Take it somewhere else that has competent help.

Your father-in-law is thinking of rope type rear main seals that were common on American car engines decades ago. On those designs, access for seal replacement included removing the oil pan. This does not apply here. Your rear main seal is a one-piece rubber on metal lip seal. Access is gained by separating the engine and transmission. The oil pan is not disturbed.

No. I doubt there’s any relation.

#5

Thanks for the replies thus far…

So what I am reading basically is that he probably didnt have to pull the oil pan on my particular type of SUV and this is probably just a “bad timing” coincidence that it is now leaking and that it probably is not his fault.

HOWEVER most if not all of you agree that the reason he gave me is not the reason its leaking (in fact the two arent related from what you are all saying) but still its probably unlikely HE caused the oil pan gasket to leak?

#6

I haven’t changed a pan gasket on anything newer than a 327 Chevy or a 351 Ford, so you may not indeed have to pull the pan gasket on the Isuzu to change the rear seal. If he didn’t pull the pan, then you can’t really blame him for this leak. Still, I don’t trust his evaluation of why it’s leaking and would have a hard time trusting him with the job.

#7

Let’s clarify.

There’s no “probably” about it - the oil pan is not pulled, not even touched, to replace the rear main seal.

The reason he gave for the current leak is wrong, but that’s irrelevant. Gaskets and seals eventually fail from age, heat, etc. - normal “wear and tear.” You know he didn’t cause the initial leaks that you had fixed. Are you finding it hard to believe he didn’t cause this one either? The car is nine years old*. It’s been five months**. There’s no plausible cause and effect***. It’s not just unlikely, but close to impossible he caused the current leak.

*And that’s why it’s developing leaks.

**Even if he had somehow caused a leak, it would have shown up within the first week or so. If you have an explanation for how it could be undetectable for five months and then suddenly be huge, I’d love to hear it.

***I have heard no evidence - for that matter, not even the slightest hint of evidence - that the current leak is in any way related to the previous repair. The mere fact that someone worked on a car does not mean that said work is the cause of all subsequent problems. There’s no case to be made here.

#8

Thats why I asked you all here. I am no car expert. I was simply given one guess from someone else (who is a retired certified mechanic but has not worked on cars for several years) that he might have to pull the pan and possibly could have seen 5 months ago that the seal needed to be replaced (or possibly SHOULD have replaced it if it was part of the tear apart to get to the rear main oil seal) but I have learned now from the posts above that he wouldnt have had to even touch it. I was just verifying the overall consensus that he did not cause the problem as it was probably just coincidential and bad timing since not everyone replied with the exact same responses as you did Gary T. I was NOT finding it hard to believe or denying a 9-year old car could have such problems by any means. It’s just when a mechanic gives you the cause that it was oil pressure that caused it even there there is no other indication of high oil pressure it does cause one to question someone’s integrity and information so that simply was why I asked for everyone’s thoughts.