Rear main seal leaks...>

[moskovita]

I just found out that my new motor, (850 miles) leak is from the rear main seal

I was hoping that it was because I was using synthetic oil and just switched to organic oil will help, but I doubt it.

So, my question is this...I have a 1,500 mile trip next week in the Vette along the West Coast and coming back through Nevada, Idaho to Seattle. Can I still make this trip, or cancell it?

The mecanic told me to take the trip and just keep an eye on the oil level. Then put new rear seals in when I get back?

What do you guys think?

I am wondering why in the heck my new motor has this problem. I don't race and have never reved above 4,000 yet.

 

[Dave L.]

oil leak,rear main seal

I would pospone if the leak is blowing oil out all over the place.If on the other hand if it's a small drip I'd keep motoring for now.By the way,is that a one or two piece main seal?Those one piece rarely go bad if installed properly.Good luck musko,I hate any engine fluid leaks but especialy oil related ones.

 

[moskovita]

Re: oil leak,rear main seal

I would pospone if the leak is blowing oil out all over the place.If on the other hand if it's a small drip I'd keep motoring for now.By the way,is that a one or two piece main seal?Those one piece rarely go bad if installed properly.Good luck musko,I hate any engine fluid leaks but especialy oil related ones.

Hey Dave, you've help me before and again...thanks!

Well, it wasn't blowing out the back or anything, just the bellhousing drip...maybe going from synthetic oil and to organic oil will help? (I just did it yesterday)

You know, I don't know about one or two piece seal? I will have to call down to Medford and find out.

Is this going to be a major fix like yanking the engine or just the Trany?

Thanks again

 

[69MyWay]

9 times out of 10, the leak is actually coming from the back corners of your valve covers. I chased a phantom rear main leak in my 90 a few months ago. Turned out the right valve cover was letting oil leak out where it puddles up in the rear corner. After I would shut the car down, that puddle would sit there and let a few drips out. It exactly mimics a rear main. Instead of the high rail heads that should be on a 90, type II block, I have Edlebrock Performer heads that have the low rail like was used on all SBC engines from 55-86. It is a horrible design. The new ones raise the rail above the oil puddle line. If you have a high volume pump, it is even worse because you are pumping so much oil up there at any given time.

Pull the valve covers, and replace the gaskets (which may just be cork) with some high quality steel center shimmed rubber vulcanized gaskets. You can get them from Summit, and Autozone. They are great, cost a little more, and among other things are also re usuable.

If you have steel valve covers/chrome make sure you have not indented the covers at the lip where they bolt down. Take a small hammer, block of wood, and anything you can fashion to make sure the sealing lip is straight and true.

Even if you have aluminum, look close and make sure they are not distorted.


Other than that, have a great trip.

 

[moskovita]

9 times out of 10, the leak is actually coming from the back corners of your valve covers. I chased a phantom rear main leak in my 90 a few months ago. Turned out the right valve cover was letting oil leak out where it puddles up in the rear corner. After I would shut the car down, that puddle would sit there and let a few drips out. It exactly mimics a rear main. Instead of the high rail heads that should be on a 90, type II block, I have Edlebrock Performer heads that have the low rail like was used on all SBC engines from 55-86. It is a horrible design. The new ones raise the rail above the oil puddle line. If you have a high volume pump, it is even worse because you are pumping so much oil up there at any given time.

Pull the valve covers, and replace the gaskets (which may just be cork) with some high quality steel center shimmed rubber vulcanized gaskets. You can get them from Summit, and Autozone. They are great, cost a little more, and among other things are also re usuable.

If you have steel valve covers/chrome make sure you have not indented the covers at the lip where they bolt down. Take a small hammer, block of wood, and anything you can fashion to make sure the sealing lip is straight and true.

Even if you have aluminum, look close and make sure they are not distorted.


Other than that, have a great trip.

You know something....you may have hit the problem! I noticed where it looked like there was a small leak at the rear of the Valve cover, right side. I will do as you say and replace the gaskets on both....I hope your right, as I was not happy thinking it may be the rear main.

Thanks Chris!

 

[moskovita]

My engine..>

 

[Dave L.]

musko- 69 is right.9 times out of 10 it is the valve covers.when i bought my car the owner said the rear main was leaking.turned out to be those pesky valve covers-no big deal fixing that.
a one piece rear main replacement would require trans removal.a two piece can be done with out removing the trans,just for your info.have a great holiday!

 

[FrankM]

If it truely is the rear main seal leaking with only 850 miles on it, then something is wrong and it will only get worse quickly. Trust me.

However as mentioned, I would verify that it is the rear main before I would tear it down.

 

[moskovita]

Okay two big questions:

musko- 69 is right.9 times out of 10 it is the valve covers.when i bought my car the owner said the rear main was leaking.turned out to be those pesky valve covers-no big deal fixing that.
a one piece rear main replacement would require trans removal.a two piece can be done with out removing the trans,just for your info.have a great holiday!

Okay two big questions:

1. Lets say it still leaks after the valve covers gasket is changed, (I hope not), then what the best way to tell if it "IS" the rear main seal before it gets torn down?

2. How can I tell if it's a one piece rear main, or a two piece main seal, without tearing it down?
(The Engine builder is in Medford, (I'm in Seattle) and my rebuild sheet doesn't specify which type of seal was used?

 

[Piet]

1) You will need to power wash your engine first. (By the looks of your picture, you are pretty close to clean... looks nice) and then start tracking the leaks. There is a UV dye you can add to your oil, run it for a couple of days and then take a UV light to trace the leak.

2) Worth the call to Medford. Two piece, cheap(er) to replace. Once piece... more money. The two piece can be replaced by removing the oilpan only. The one piece.... well ... there is a whole bunch of other stuff you could check while you got all that open....

Good Luck!

 

[JohnZ]

If your block is prior to '86, it has the 2-piece seal; all it takes to change it is dropping the pan and the rear main cap. If you don't follow the Shop Manual procedure EXACTLY and put sealer on the (clean and dry) corners of the mating surfaces between the cap and the block, chances are it will leak. Any reputable engine builder should know better, and should fix it free.

 

[moskovita]

Some great info here...this really helps!

Thanks for all of you taking the time to answer my questions.

 

[moskovita]

I forgot to add...does having a automantic make any difference in the above?

 

[69MyWay]

I forgot to add...does having a automantic make any difference in the above?

No difference.

I do see you have chrome plated steel valve covers. I bet that is your problem!

Make sure you not only have the super high quality rubber gasket, but also the wide spread hold down clamps, and no distortions in the sealing lip from overtightening. Also, it may be as simple, as they NEED to be tightened a tad now that you have heated and cooled the engine a number of times since the rebuild.

 

[Buckskin7T7V]

No

 

[Bob Chadwick]

Seems to me that the best way to track this down is to return it to the mechanic that did the work. I wouldn't spend any time trying to figure this out with a brand new engine. I would also take the trip and monitor the oil level as your mechanic indicates. Wouldn't hurt to have a witness when he tells you this.


By the way, Your car and engine compartment make me green with envy.

Bob

 

[Bob Chadwick]

Beautiful country out there. I just got back from a business trip to Portland that allowed me to take 101 up the coast to Gray's Harbor. Didn't have my Vette but the Maxima was fun to drive.

Bob

 

[jsimpson]

If you were trying to break your new engine in with synthetic oil, that is the problem. Synthetic oil will NOT allow the rings and cylinders to wear enough to fit each other (ring seating). Drain and flush your engine and fill it with dino oil and drive it until it stops using oil. Your rings will be seated and THEN you can switch to synthetic! Blowby is causing high crankcase pressure thereby blowing oil past your rear main seal.

 

[moskovita]

If you were trying to break your new engine in with synthetic oil, that is the problem. Synthetic oil will NOT allow the rings and cylinders to wear enough to fit each other (ring seating). Drain and flush your engine and fill it with dino oil and drive it until it stops using oil. Your rings will be seated and THEN you can switch to synthetic! Blowby is causing high crankcase pressure thereby blowing oil past your rear main seal.

Okay, as of today, both things have been done....
1. Changed the valve cover gasket to steel center shimmed rubber vulcanized gaskets.
2. Drained and flushed my engine and filled it with dino oil.

Now, will sit back and watch what happens and keep fingers crossed.

 

[JohnZ]

If your engine builder used moly-faced rings, they seat in five minutes, and oil type won't make any difference; Vipers, C5 Corvettes, and most other high-performance cars use moly-faced rings, and use synthetic oil as factory fill.

Did you run a bead of sealer around the top surface of the valve cover gaskets to seal them to the covers before installing them? When they leak, they leak between the cover and the gasket, not between the gasket and the head, unless the head seal surface is in really bad shape.