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ChevyMan
07-13-2008, 08:07 PM
My '76 Impala has been leaking at the rear main bearing seal for many years but I'm checking the oil dipstick at least on the average, twice a week to assure the oil level in the crank case doesn't get too low and having to add about a cup or less every 5 or 6 weeks rather than spending four, five hundred (or more, bucks)to have a new oil seal installed.

I've been wondering if there also is an oil seal at the front end of the crank case where it also is showing some leakage as evidenced on the oil stains on the garage floor.
Any input will be appreciated.


Larry T

Disco Man
07-14-2008, 12:34 PM
Larry,

What motor do you have in your Impala?

ChevyMan
07-14-2008, 03:50 PM
Pete, by "motor", I presume you mean number of cylinders ?

It's a 350 CID V-8

Larry T

Disco Man
07-14-2008, 04:35 PM
ChevyMan,

That's exacly what I was looking for. Your 350 CID is a Chevy small block V8, and yes there is a seal up front. Look around the area of the behind the waterpump it may be leaking there or it may be leaking in the front part of the oil pan where it meets the engine block there's a seal/gasket there.

I would not worry about replacing any seals until you are putting in a quart of oil every two weeks. Generally on a motor as old as yours it is going to have leaky seals especially the rear seal. If you plan on keeping the car and it has a lot of miles on it and the leaking gets worse, you may want to just get the engine rebuilt and thereby all the seals will be replaced. If the motor has low mileage on it and the leaking gets worse you can just replace the seals.

chiph
07-14-2008, 06:26 PM
What's the cost difference between a rebuild and buying a long-block crate motor?

Chip H.

Disco Man
07-14-2008, 06:38 PM
What's the cost difference between a rebuild and buying a long-block crate motor?

Chip H.



Chip,

Excellent point. For a block that they still currently make like the Chevy 350 - available in a few different peformance levels over the counter at any GM parts seller, they come at a reasonable price. It would probably cost as much for Larry to rebuild his 350 then to put a brand new one in which would have more horsepower and torque and have a full warranty. However Larry would lose his numbers matching motor which would lower the value of his car as prices of mid 1970s Impalas climb.

Check out the prices and different performance levels of new Chevy 350 V8s (notice how the 355 horsepower ZZ4 350 V8 is a little over $4K which is a great deal):

http://www.crateenginedepot.com/

ChevyMan
07-17-2008, 07:29 PM
ChevyMan,

That's exacly what I was looking for. Your 350 CID is a Chevy small block V8, and yes there is a seal up front. Look around the area of the behind the waterpump it may be leaking there or it may be leaking in the front part of the oil pan where it meets the engine block there's a seal/gasket there.

I would not worry about replacing any seals until you are putting in a quart of oil every two weeks. Generally on a motor as old as yours it is going to have leaky seals especially the rear seal. If you plan on keeping the car and it has a lot of miles on it and the leaking gets worse, you may want to just get the engine rebuilt and thereby all the seals will be replaced. If the motor has low mileage on it and the leaking gets worse you can just replace the seals.


>>> If you plan on keeping the car and it has a lot of miles on it <<<

I'm planning to keep the car as long as it is able to run with available replacement parts since I don't care much for these new cars coming out.


>>>-----and the leaking gets worse----<<<


So far , the leaks are miniscule and it is more cost effective to just keep topping off the oil in the crank case as compared to the cost of a rebuild job which can run into hundreds of dollars (oil costs $3.29 a qt).


>>>If the motor has low mileage on it and the leaking gets worse you can just replace the seals<<<


I don't do much driving, high cost of gas or not.Odometer reads 52,720. The leaks, besides at the rear main bearing oil seal, is at the front of the engine in the vicinity of the harmonic balancer or vibration damper, what ever they call it.

Disco Man
07-18-2008, 11:52 AM
ChevyMan,

Wow that's some low mileage for a 1975 model year car. You Impala sounds like a keeper. My favorite full-size Chevy is the 1971 - 1976 Impala/Caprice. I learned to drive on a 2-door (with the concave rear window) 1972 Caprice. The car had a great ride and good power (400 sbc). I was sad when my dad sold it two years after I got my license.

Here's a 1972 Caprice just like the one I learned to drive on:

http://media.motortopia.com/files/2395/vehicle/4578b9c6bab25/tn_xlarge_3683_1.jpg

J. ZIMM
08-17-2008, 02:30 AM
:) Some of the older engines had a braided rope type seal in the rear. They were inpregnated with a graphite material. After a few years, and milage did not seem to have any bearing on this, they would seem to dry out, or form a hard carbon around the inner part of the seal. There have been some products on the market that claim to soften up this type of seal and disolve the carbon. Be real careful using thess types of additives as they can also loosen up carbon from other parts of the engine. If your car only has 52K, the seals may be dried out to the point that they 'may' soften up to be usable. But my guess will be that both the seals and the gaskets have dried out from setting. Seals and gaskets will dry out from lack of use. Espeacially in an araa that has low humidity and lots of heat. The rear seal is a challenge to replace, but it can be done with the engine in the car. I do not recomend it to a novice. The front seal can be done with a little boning up with a good repair manual. If you do the front seal yourself , be sure to clean all sufaces down to the mating surfaces, and the "tin is straight". The front seal needs to be installed straight and all the way in till it seats. Maybe a friend that has done this before will help you along. I've always been one to try to help someone along whenever possible. And I also agree. The car is a keeper. these ol' boats are so much better in many respects. I have a couple of them myself.. Good luck in which ever way you decide. 8)

DonTom
08-17-2008, 04:29 AM
"add about a cup or less every 5 or 6 weeks"

A quart every few months and you worry about it?

Back in the late 1970's, I owned a 1971 307 Chevy Malibu that ate a quart of oil every two days and I lived with it for about a year after! And it didn't leak a drop!

What happened was the timing chain fell off the worn nylon gear sprocket and the values got damaged. With the help of my Volts Wagon mechanic next door neighbor, we replaced the valves after I removed the heads. After the work was done the compression must have gone up so much that the oil rings could not handle it. I found no evidence of an oil leak anywhere, but I had to add a quart every other day in normal driving, perhaps less than every hundred miles.

The thing had so much power after that it seemed unreal. The only problem was the ridiculous oil consumption, but it took me about a year to junk it after that. I just carried several bottles of oil in the trunk.

-Don-

Eric
08-17-2008, 08:00 AM
"What happened was the timing chain fell off the worn nylon gear sprocket and the values got damaged. "

Hey, maybe it's a job for Gail? :P

DonTom
08-17-2008, 10:06 AM
"Hey, maybe it's a job for Gail? "

I am surprised you even noticed that! Not even your spellchecker could catch that! Not even if it worked!

-Don-

grouch
08-17-2008, 01:42 PM
"add about a cup or less every 5 or 6 weeks"

A quart every few months and you worry about it?

Back in the late 1970's, I owned a 1971 307 Chevy Malibu that ate a quart of oil every two days and I lived with it for about a year after! And it didn't leak a drop!

What happened was the timing chain fell off the worn nylon gear sprocket and the values got damaged. With the help of my Volts Wagon mechanic next door neighbor, we replaced the valves after I removed the heads. After the work was done the compression must have gone up so much that the oil rings could not handle it. I found no evidence of an oil leak anywhere, but I had to add a quart every other day in normal driving, perhaps less than every hundred miles.

The thing had so much power after that it seemed unreal. The only problem was the ridiculous oil consumption, but it took me about a year to junk it after that. I just carried several bottles of oil in the trunk.

-Don-





I'm surprised an electric car mechanic knew how to work on an internal combustion engine. I don't think I've evern seen a Volts Wagon though. ;D

DonTom
08-18-2008, 08:57 AM
"I'm surprised an electric car mechanic knew how to work on an internal combustion engine. I don't think I've evern seen a Volts Wagon though. Grin"

You're a better spellchecker than the one we have here, even when it works!

-Don-

J. ZIMM
08-19-2008, 11:22 PM
:D Hey maybe I'll take my car to a Volts Wagen mekenic. That should be a shocking experience, doncha think? :P