Oil Pan Plug Gasket on 76

[Rick B.]

So recently had my 76 Judged and one of the minor comments/points loss was that the Plug and gasket were not original. I have the original plug, but not sure what is considered the proper gasket/washer. Was it rubber or a white plastic looking gasket? Tried to find it in the judging manual with no success. Maybe I am not looking in the right place.

[Joe L.]

Re: Oil Pan Plug Gasket on 76

So recently had my 76 Judged and one of the minor comments/points loss was that the Plug and gasket were not original. I have the original plug, but not sure what is considered the proper gasket/washer. Was it rubber or a white plastic looking gasket? Tried to find it in the judging manual with no success. Maybe I am not looking in the right place.

Rick------


It was a off-white, nylon (plastic) washer-like gasket about 3/32" in thickness. It's OD extended slightly beyond the OD of the oil plug flange. The original GM part number was 3921989 but it's long since GM-discontinued.

[Duke W.]

Re: Oil Pan Plug Gasket on 76

You can buy similar aftermarket gaskets, but they are too soft, get crushed and leak.

Duke

[Joe L.]

Re: Oil Pan Plug Gasket on 76

You can buy similar aftermarket gaskets, but they are too soft, get crushed and leak.

Duke

Duke------


That's because these aftermarket replacements are not made of nylon. They are some kind of low durometer rubber material.

[Joe L.]

Re: Oil Pan Plug Gasket on 76

GM "experimented" with a variety of drain plug gaskets over the years and never came up with a leak-proof solution.

1955-1986 used a nylon gasket. While there were a few different part numbers over the years, the gasket was essentially the same. These leak no matter what you do.

About 1987, I think they went to a soft copper gasket, for PRODUCTION and earlier SERVICE. I'm not sure of the material and tenure of this gasket, though. In any event, it was short-lived and by 1988 was replaced by a gasket that was a somewhat sophisticated composite of elastomer and metal. This gasket, GM #14090908, is still available to this day to SERVICE all 1955-96 Corvettes. When I first became aware of this gasket many years ago I thought that GM had finally solved the gasket leak problem. I was wrong. These leak, too.

Although never cataloged for any 1955-96 Corvette, GM went to another design for other applications. This design uses a special drain plug with an annular groove into which seats a rubber gasket (which is replaceable). The design of the plug controls compression of the gasket and prevents over-compression. When I first became aware of this design I thought that GM had finally solved the gasket leakage problem. I was wrong again. These leak too. This design with 1/2-20 thread (beware: some are metric) can be used on 1955-96 Corvettes.

Attached are some photos of the GM #14090908 gasket and the later style rubber gasketed plug I described above.

[Terry M.]

Re: Oil Pan Plug Gasket on 76

Joe
I don't understand why you are having issues with 14090908. All my Caprices use this gasket and it works just fine, and I don't even use a torque wrench for the oil pan plug. Maybe the key is to loosen and then tighten them frequently. At nearly 300K on two of the 1995 Caprices I have lost track of how many times I have changed the oil, although I could look that up in the maintenance records. I will confess to changing the gaskets when I first got the cars from their public service, but that was nearly 200K miles and 18 years ago.

[Jim T.]

Re: Oil Pan Plug Gasket on 76

Joe, On my 1996 Monte Carlo it uses a oil plug with recessed gasket. I used a M12 Dorman part number 66451 rubber gasket and used a inch pound torque wrench to not over tighten the oil plug, The drain plug still a drop of oil not a whole lot if you wipe it every day after it is driven. Oil plugs do not need much torque to tighten. I think 20 is the number.

[Joe L.]

Re: Oil Pan Plug Gasket on 76

Joe
I don't understand why you are having issues with 14090908. All my Caprices use this gasket and it works just fine, and I don't even use a torque wrench for the oil pan plug. Maybe the key is to loosen and then tighten them frequently. At nearly 300K on two of the 1995 Caprices I have lost track of how many times I have changed the oil, although I could look that up in the maintenance records. I will confess to changing the gaskets when I first got the cars from their public service, but that was nearly 200K miles and 18 years ago.

Terry------

I don't generally use a torque wrench, either, although I have used one several times to see if applying correct toque would solve the problem. It did not. The gasket does not leak a lot, just enough to leave a film on the pan surrounding the plug. I also replace the gasket every time so it's not as if a worn gasket is the problem.

[Joe L.]

Re: Oil Pan Plug Gasket on 76

Joe, On my 1996 Monte Carlo it uses a oil plug with recessed gasket. I used a M12 Dorman part number 66451 rubber gasket and used a inch pound torque wrench to not over tighten the oil plug, The drain plug still a drop of oil not a whole lot if you wipe it every day after it is driven. Oil plugs do not need much torque to tighten. I think 20 is the number.

Jim-----

With the plugs with the recessed rubber gasket it's virtually impossible to over-torque them. The design of these plugs causes the perimeter of the plug flange to contact the pan. This controls the compression of the gasket. The torque value for this type drain plug is 22 lb/ft.

[Rick B.]

Re: Oil Pan Plug Gasket on 76

Thanks everyone I appreciate your input.

[Patrick H.]

Re: Oil Pan Plug Gasket on 76

Although never cataloged for any 1955-96 Corvette, GM went to another design for other applications. This design uses a special drain plug with an annular groove into which seats a rubber gasket (which is replaceable).

Part number for replaceable gasket?

My 2008 leaks a bit too, and if I could replace this gasket with oil changes I'd give it a try.

[Joe L.]

Re: Oil Pan Plug Gasket on 76

Part number for replaceable gasket?

My 2008 leaks a bit too, and if I could replace this gasket with oil changes I'd give it a try.

Patrick------


GM #12616850. GM #3536966 should also work.

However, if your experience is like mine, you'll probably have the same seepage after you replace the gasket. However, it's worth trying.


P