[Fullback66]

After a Michigan winter hibernation, I looked under the GTO to see quite a bit of oil/maybe tranny fluid on the ground. Is this common for gaskets to rot after long winter breaks? You can see in the pictures the drips on the oil pan and the tranny. My car used to sit for 9.5 months and be driven for 2.5 months. I did that for years. I have a feeling I destroyed the gaskets by the long breaks. It does not sit like that anymore. I drive it for about 7 months.

What do you guys think? Time to pull out the engine and get a new oil pan gasket?

Any suggestions or ideas would be great.

Thanks,
FB66

[GT182]

No... it's the rear main seal in the back of the engine that leaking. They do that. How much oil do you add every time you take it out for a run? You're gonna have to pull the engine or transmission to fix it. It can't be fixed with either one in the car... unless someone knows of a good oil additive to use. I say it's best to pull the engine.

If the tranny is leaking too, it's best to have it out too to check it over and fix the leaks.

[Greg Reid]

Could be the rear main...could be valve covers. First things first. Clean the underside of the car thoroughly, run it and find out where it's coming from. No way I'd change a rear main without verifying that it's leaking.

[6x400gmc]

Originally Posted by Greg Reid

Could be the rear main...could be valve covers. First things first. Clean the underside of the car thoroughly, run it and find out where it's coming from. No way I'd change a rear main without verifying that it's leaking.

Agreed. Valley pan or distributor could also be the culprit. The rear lean of the engine will cause everything to pool towards the rear, fooling you into thinking you have a rear main or oil pan gasket leak. Clean and recheck.

Britt

Sent from my SM-N950U using Tapatalk

[GT182]

If it is valve cover gaskets you'd see oil on the sides of the engine and bell housing and not under the flywheel cover. From there it's more likely to end up in the transmission too. I've never seen and oil leak from the distributor unless there's no gasket or there's a crack in the block. Valley pan maybe, but you can reach in there to check.

The best way to check the rear main is to pull the flywheel cover. You'll see oil all over the place. Do that first. there's only a couple of bolts to get it off.

[mcmurb]

Looks like oil on your exhaust too. may want to check your oil filter area.

[Fullback66]

Mcmurb- I did check the filter area. It is ok. Not sure why there is oil on the pipe.

GT. Great advice. I will give that a look.

Thanks Guys
FB66

[Greg Reid]

Originally Posted by GT182

If it is valve cover gaskets you'd see oil on the sides of the engine and bell housing and not under the flywheel cover. From there it's more likely to end up in the transmission too. I've never seen and oil leak from the distributor unless there's no gasket or there's a crack in the block. Valley pan maybe, but you can reach in there to check.

The best way to check the rear main is to pull the flywheel cover. You'll see oil all over the place. Do that first. there's only a couple of bolts to get it off.

Gary, here's why I say to be sure...I had a nice '78 Bonneville that I was positive needed a rear main. It was leaking just like you describe, out of the inspection cover and back of pan was soaked.
I actually set a day aside to go to a friend's to do it because he had a lift. We put it up, ran it and oil was pouring out of the BACK of the valve covers. The rest of the engine was dry. What a relief that was!
The valve cover gaskets crumbled when we took them out.
And just to add a little color to the story...

[mcmurb]

similar story with my 67. Was pulling the engine anyway, and when i got it on the stand to look it over closely, found the leaky rear valve covers. PO had torqued the screws with all he could muster bending the covers and crushing the gasket.

[GT182]

I understand Greg. But... until FB66 takes the valve covers off and checks the gaskets we won't know. Same for the distributor too. Tho it is possible it's gasket is shot or non existent. That said any oil leakage will be on the bell housing and down it's side, but not necessarily dripping off the fly wheel cover.

Any how, I still stand but my deduction on the rear main seal. Only because of what I see and what I have seen on various engines over they years. Time will tell.

BTW, I asked my race car buddy Saturday what he thought and showed him FB66's photos. His answer was the same as I've said. OG 67 more or less agreed with me too.

That's one gorgeous 78 Bonneville Greg.

[Greg Reid]

I'm not saying you're wrong Gary...It may very well be a rear main...What I'm saying is that if it were me, I would check the valve cover gaskets before pulling the engine. I'm funny like that though....lol

[GT182]

No no, I understand Greg. I know what you mean. I check everything on my car just to make sure I don't leave a mess any where other than my garage.

[GT182]

Ok. I talked to 2 engine builders this morning. I showed them the photos of the oil leak and told them what everyone is saying. Both agreed.... rear main seal leak. Valley pan, distributor, and valve covers never came into the discussion from them. Those would show oil in totally different places.

They both said it's time to pull the engine and do it the right way. And while it's out you can check the tranny's front seal, but they don't think it's leaking from the looks of the oil.

[Fullback66]

Good info. Thanks