95 Chev Lumina / REAR MAIN SEAL

[SFCP]

Yep, you guessed it, the rear main seal on my 95 Lumina is leaking. Mechanic tells me its not bad enough to be worth fixing right now. So, basically, I'm getting quarter sized oil puddles on my garage floor, but it's not even leaking enough to worry about adding oil between OCI's. Not yet anyway. Now I'm pondering the Castrol HM or the Valvoline HM and stuck as to which one to use. Tallpaul provides a really good sales pitch for the Valvoline HM with its PAO and moly content, plus its advertised as synthetic blend. Castrol HM is not marketed has heavily as the Maxlife. I know I couldn't go wrong with either choice, but I’m leaning toward the Castrol.
I hope this rear main seal doesn't mean my car is in the twilight of it's life on earth, but correct me if I'm wrong….Do many car engines outlast minor leaks like this where the main seal never gets much worse than it already is?

 

[wgtoys]

Weaping oil seals are very common, and are not a sign of impending doom. If you Lumina is a V-6 I would be much more concerned about the intake manifold gasket failing and letting antifreeze into the motor oil.

Trying a HM oil is what I would do in your situation, and getting an annual UOA to check for the start of intake manifold gasket failure would be high on my list as well.

 

[SFCP]

Quote:

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Weaping oil seals are very common, and are not a sign of impending doom. If you Lumina is a V-6 I would be much more concerned about the intake manifold gasket failing and letting antifreeze into the motor oil.

Trying a HM oil is what I would do in your situation, and getting an annual UOA to check for the start of intake manifold gasket failure would be high on my list as well.

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That's what I will do. My mech told me the intake seals look great and are dry. I actually had them replaced when I bought the car with 50k in 2000. But a UOA could not hurt.

 

[mstrjon32]

In my experience, with this engine, many mechanics misdiagnose a leaking oil pump drive o-ring seal as a rear main leak, since the oil leaks out of the o-ring seal and all over the rear of the engine. Shine a flashlight down behind the throttle body and look to see if you've got a puddle of oil forming near the oil pump drive. Replacing this o-ring is a walk in the park compared to replacing the rear main.

I'm assuming you've got a 3.1L Lumina. The 3.4L suffers from the same condition, however, replacing the o-ring on this engine is much more difficult, and I'd probably bring it to a shop to have it done. It requires removing the rear cylinder head.

 

[SFCP]

Quote:

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In my experience, with this engine, many mechanics misdiagnose a leaking oil pump drive o-ring seal as a rear main leak, since the oil leaks out of the o-ring seal and all over the rear of the engine. Shine a flashlight down behind the throttle body and look to see if you've got a puddle of oil forming near the oil pump drive. Replacing this o-ring is a walk in the park compared to replacing the rear main.

I'm assuming you've got a 3.1L Lumina. The 3.4L suffers from the same condition, however, replacing the o-ring on this engine is much more difficult, and I'd probably bring it to a shop to have it done. It requires removing the rear cylinder head.

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I looked behind the throttle body, and could not see where any sort of an O ring is. I do have the 3.1L V6. I'm assuming the throttle body is that part which has the half moon shaped piece of metal on it with thin cables attached... I looked behind it, but all I can see are thin metal tubes, and an exhaust shield cover. Am I looking correctly?

 

[SFCP]

Quote:

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Quote:

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In my experience, with this engine, many mechanics misdiagnose a leaking oil pump drive o-ring seal as a rear main leak, since the oil leaks out of the o-ring seal and all over the rear of the engine. Shine a flashlight down behind the throttle body and look to see if you've got a puddle of oil forming near the oil pump drive. Replacing this o-ring is a walk in the park compared to replacing the rear main.

I'm assuming you've got a 3.1L Lumina. The 3.4L suffers from the same condition, however, replacing the o-ring on this engine is much more difficult, and I'd probably bring it to a shop to have it done. It requires removing the rear cylinder head.

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I looked behind the throttle body, and could not see where any sort of an O ring is. I do have the 3.1L V6. I'm assuming the throttle body is that part which has the half moon shaped piece of metal on it with thin cables attached... I looked behind it, but all I can see are thin metal tubes, and an exhaust shield cover. Am I looking correctly?

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Or could someone give me a better visual when I'm looking at the top of this 3.1L where the oil pump is so that I can go look at it again?

 

[mstrjon32]

It might be a little hard to visualize, but here is a photo of the 3100 engine in my 1997 Monte Carlo partially disassembled. The red arrow points to the oil pump drive, and the general area where you are looking for leaks. Imagine the lower intake manifold is in place, and then imagine the throttle body above the oil pump drive.

I can try and take a better photo for you in a day or two, if this doesn't help.

 

[SFCP]

Thanks for the pic. I looked in that are, but could see no visible moisture, but I will be sure to have my mechanic look for that o-ring. I'm sure he will know what I'm talking about

 

[hominid7]

You could try not changing your oil but once a year to allow for some protective sludge to build up to help fill the leak.

Sorry, couldn't resist

 

[Merkava_4]

The Castrol is one half cSt thicker than the Maxlife; whether that's a huge difference, I don't know. And then of course we don't know Castrol's cSt number at 40 degrees Celcius because that won't tell us. And another thing: we don't don't know exactly what's in HM Castrol; how much Group III or IV does it have? I haven't a clue.

 

[mstrjon32]

I think if his leak is significant enough that it's creating a puddle on the ground each night, even maple syrup would leak out of the engine, so a slightly thicker oil isn't going to help.

This is one of those problems that is going to have to be fixed "the right way", IMO.

 

[SFCP]

Well, I'm not about to drop the transmission just to have the rear seal replaced... that's about a 900.00 job. Forget about that. My shop told me that unless it's dumping a quart of oil on the ground (they were exagerating a little) not to worry about it.

 

[mstrjon32]

I personally doubt its your real seal, but there is no way to know without looking at the car. I'm not saying it doesn't happen, but for all the 60* engines I've seen, they're always leaking from either the oil pump drive seal or from the LIM where it is necessary to use sealant, and not a gasket (in the valley between the cylinder heads).

That said, I let my '97 Monte leak for almost a year before I had the time to fix it, so it's not like its a priority.

 

[m2200b]

Just use simple green and and good hosing of the area when you wash the car.

 

[mstrjon32]

Make sure you use it on a cold engine though, and hose it off quickly after putting it on. Simple Green will do some funky things to aluminum. Nothing bad will happen mechanically, but your engine will look weird.

 

[eljefino]

Wife's 93 corsica did this and ran fine up to and beyond 207,000 miles so letting it go is an ok solution.

As others said, and I agree, there's a "stump" where the distributor used to be that they plugged with an often-leaking o-ring. The bottom half of the old dizzy shaft still serves as an oil pump. This is a common failure and under a bunch of stuff on the corsica so I let it be.

Note GM revised the engine in 96, renaming it "3100", and that's when the intake gaskets really started going bad. The older, less powerful "3.1" is somewhat easier on them.

 

[mstrjon32]

IIRC, the 3100 became available in 1994 in select Buicks and Oldsmobiles. A friend of mine used to have a 1994 Century wagon with a 3100.

I don't know what the deal was with GM, but the quality on these engines got worse and worse until they finally overhauled them with the 3500 and 3900. In the late '80s, the 2.8 and 3.1 MPFI were bulletproof engines (though the #@$%! oil pump drive o-ring still leaked), then they moved to the new style gaskets with the 3100, then to the roller rockers, which you'd think would smooth things out, but all the roller rocker 60*'s I've heard from the '90s, including my 1997, are louder than the original design; then the Dexcool which may or may not have lead to the gasket failures; and then at some point in the mid-90's they changed their production methods and it seems like every 60v6 since then suffered from piston slap.

Some of the last 3400's, the 2002+ ones, seem to be much better quality wise, but the older ones were just as flawed as the 3100. The new 3500 and 3900 have so far proven themselves to be great engines (though they still use the #@$%! o-ring, and I'm sure they will leak) and I'd recommend a vehicle equipped with one in a heartbeat.

 

[onion]

+1 on the o-ring suggestion. I was sure the crank seal on my '94 Corsica was leaking- I looked a little harder and turns out it's that o-ring. I changed it years ago, and it's leaking again. GM has since come out with a new and improved o-ring that's supposed to solve the problem.

GM started the 3100's in '94, upgraded to roller rockers in '96, then changed the cylinder heads and intake design again around '99 or '00. They're a cheap, reliable, and reasonably powerful engine... with a few bothersome inherent problems.

That o-ring is more or less 'under' the throttle body. With a flashlight and some determination, you can get a reasonably good look at it with the engine fully assembled.

 

[SFCP]

I finally saw it, yes, mine is leaking, too. I asked my mechanic about it....his reply "Sure Mark, if you want to pay me to replace it, I can, but it's not worth it unless your car is puking a quart of oil onto the ground"....

Guess he's honest, and doesn't want to see me needlesly spend money.

 

[mstrjon32]

Quote:

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I finally saw it, yes, mine is leaking, too. I asked my mechanic about it....his reply "Sure Mark, if you want to pay me to replace it, I can, but it's not worth it unless your car is puking a quart of oil onto the ground"....

Guess he's honest, and doesn't want to see me needlesly spend money.

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As I suspected, then. If you have any mechanical ability and a free weekend, you can definately do the job yourself. It is up there on the easiest to do engine jobs list. You will need to remove the throttle body, but once you have direct access to the oil pump drive, it's simply a matter of removing one bolt, pulling it up and out of the engine, replacing the seal, and reinstalling everything.