C1 Oil Pan Drain Plug Gasket

[Rick C.]

Does anyone know of a source for oil pan drain plug gaskets that match the description in the 58-60 and 61-62 TIM&JG? Requirements are an OD of just under 7/8" and a thickness of 1/32". Those gaskets I find with the proper OD are .060" to .070" thick. It doesn't seem to me that a .060" gasket will crush to .032" when installed. Or will it?

Thanks!!
Rick

[Richard M.]

Re: C1 Oil Pan Drain Plug Gasket

Rick, If you could get gasket material that color and dimension, it'd be best to make several yourself, no?

[Rick C.]

Re: C1 Oil Pan Drain Plug Gasket

Thanks, Rich! It's a good idea worth pursuing.

Rick

[William F.]

Re: C1 Oil Pan Drain Plug Gasket

Can't get it from GM? Anything close at parts houses-NAPA, etc or from a Corvette vendor? Just one that will work?

[Bob J.]

Re: C1 Oil Pan Drain Plug Gasket

If that .030 bothers you, you can always sand the .060 gasket down .028 to be in compliance.
I think if you have the OD correct, nobody will notice or care if it's slightly thicker.
Bob Jorjorian

[Rick C.]

Re: C1 Oil Pan Drain Plug Gasket

Thanks, Bob. Probably the best bet is to try sanding and if I can't get even thickness all they way around I'll just go with a thicker gasket.

Rick

[Joe L.]

Re: C1 Oil Pan Drain Plug Gasket

Thanks, Bob. Probably the best bet is to try sanding and if I can't get even thickness all they way around I'll just go with a thicker gasket.

Rick

Rick------


Keep this in mind: GM didn't replace the earlier thinner gasket with the later thicker one because the thinner one worked just as well.

As a matter of fact, neither the earlier or later style gaskets are what I would call "leak proof". There are even later design gaskets which can be used but they're not "leak proof" either. For some reason, GM never came up with a leak-proof gasket.

[Richard M.]

Re: C1 Oil Pan Drain Plug Gasket

Joe, GM never did, but NAPA did. NAPA Part# 7041093

Screenshot_20240523_032738_Chrome.jpg

I have used these on leaky original 1956 to 1967 cars which never leaked after using these. I once rebuilt a 427 L71, using a NOS sevice GM oil pan. Little did I know, this pan would drip slightly after engine temperature normalization. After a frustrating diagnosis, I surmised that the weld seam of the internal threaded weld-nut to the sheet metal was offset slightly, deeming it a "forever-leaker".

After draining and retrying different drain plug gaskets, with no fix, I was now looking at pulling the pan on a completed restoration.

I was at my NAPA store and mentioned my dilemma, ordering a new pan to block gasket set, when my store manager walked over and tossed a bag of theses at me.

He said this will stop the drips!

Sure enough, it worked! Problem drip solved.

Rich

[Mark E.]

Re: C1 Oil Pan Drain Plug Gasket

Joe, GM never did, but NAPA did. NAPA Part# 7041093

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I have used these on leaky original 1956 to 1967 cars which never leaked after using these. I once rebuilt a 427 L71, using a NOS sevice GM oil pan. Little did I know, this pan would drip slightly after engine temperature normalization. After a frustrating diagnosis, I surmised that the weld seam of the internal threaded weld-nut to the sheet metal was offset slightly, deeming it a "forever-leaker".

After draining and retrying different drain plug gaskets, with no fix, I was now looking at pulling the pan on a completed restoration.

I was at my NAPA store and mentioned my dilemma, ordering a new pan to block gasket set, when my store manager walked over and tossed a bag of theses at me.

He said this will stop the drips!

Sure enough, it worked! Problem drip solved.

Rich

The threaded nut inside of the pan is not sealed to the drain hole on any V8 Chevy pan I've seen. This means leaks are not through the threads, and no amount of extra tightening or use of thread sealer will many ANY difference. The only sealing surface is between the back of the drain plug head and the outside of the pan. That's why a new crush washer is critical for a drip-free experience.

[Patrick H.]

Re: C1 Oil Pan Drain Plug Gasket

The threaded nut inside of the pan is not sealed to the drain hole on any V8 Chevy pan I've seen. This means leaks are not through the threads, and no amount of extra tightening or use of thread sealer will many ANY difference. The only sealing surface is between the back of the drain plug head and the outside of the pan. That's why a new crush washer is critical for a drip-free experience.

FYI, I've used these and still had leaks.
GM has actually used these at one point in the past. I don't think they were a NAPA invention. You can buy them at AutoZone, etc too.
The oil drain on my C6 with the rubber replaceable gasket? Still leaks.

[Duke W.]

Re: C1 Oil Pan Drain Plug Gasket

I'm amazed that a modern car (and I consider C6 to be modern) still has a leaky oil pan drain plug gasket. Didn't GM management decree "no leaks" back in the eighties, which led to the one piece rear main seal?

It is possible to have a leak free gasket. My '91 MR2 has a stamped steel oil pan. The gasket is relatively thin plated steel with what appears to be a heavy gasket paper coating on both sides. It should be replaced every time, but I've installed a used one in good condition at least once, and it did not leak. In fact with an ID of about 1/2" and OD of about 13/16" it might even work on a vintage Corvette for a leak free seal.

My '88 MBZ 190E 2.6 has a cast aluminum oil pan with an steel insert for the drain plug. The gasket is soft copper designed to be replaced every time, but I can simply dress down both sides on some 220 paper to eliminate the slight galling, and they can be reused multiple times.

Duke

[Richard M.]

Re: C1 Oil Pan Drain Plug Gasket

The threaded nut inside of the pan is not sealed to the drain hole on any V8 Chevy pan I've seen. This means leaks are not through the threads, and no amount of extra tightening or use of thread sealer will many ANY difference. The only sealing surface is between the back of the drain plug head and the outside of the pan. That's why a new crush washer is critical for a drip-free experience.

Mark, Yes you are correct, but the problem on this one was the weld nut was installed creeping upbthe rear vertical wall of the pan, which disallowed the flat of the weld nut from sitting perctly flat on the bottom horizontal sheet metal of the pan. Thie drip was gone with those rubber impregnated thick steel washers. This gave reinforcement to the drain plug.

Rich

[Richard M.]

Re: C1 Oil Pan Drain Plug Gasket

I'm amazed that a modern car (and I consider C6 to be modern) still has a leaky oil pan drain plug gasket. Didn't GM management decree "no leaks" back in the eighties, which led to the one piece rear main seal?

It is possible to have a leak free gasket. My '91 MR2 has a stamped steel oil pan. The gasket is relatively thin plated steel with what appears to be a heavy gasket paper coating on both sides. It should be replaced every time, but I've installed a used one in good condition at least once, and it did not leak. In fact with an ID of about 1/2" and OD of about 13/16" it might even work on a vintage Corvette for a leak free seal.

My '88 MBZ 190E 2.6 has a cast aluminum oil pan with an steel insert for the drain plug. The gasket is soft copper designed to be replaced every time, but I can simply dress down both sides on some 220 paper to eliminate the slight galling, and they can be reused multiple times.

Duke

My '07 LS2 oil pan to block seal started leaking about a year after power train warranty ran out.

All LS engine had issues, allegedly due to inadequate sealant, robotically applied at engine assembly.

We talked about this slot over at CF. Very frustrating.

To pull the pan, one has to pull the balancer. To pull the balancer, one has to pull the steering rack.

Iirc, around 6-7 labor hours. About a grand at the dealer back then.

I opted to let it drip, and clean it up every once in a while.

Like my '59 with a LS-283(knuck-knuck), which used to do during the 35 years I owned it.

LS? LS="Leaky Stuff"

If a LS Engine doesn't leak oil, that means there's no oil in it.

Rich

[Joe L.]

Re: C1 Oil Pan Drain Plug Gasket

Here's the story:

The original 1955-67 engine oil drain plug gasket, PRODUCTION and SERVICE, was GM #516975. I believe this gasket was of nylon material. This gasket leaked. It was discontinued from SERVICE in December 1968 and replaced by GM #3921989 which was also a nylon gasket very similar to its predecessor. This gasket leaked, too.

The 3921989 continued to be used in PRODUCTION throughout the C3 era and the early C4 era. It was discontinued from SERVICE in June, 1986 and replaced by GM #14079550. This gasket is a composition metal/rubber piece similar to the NAPA gasket described and pictured by Rich. It was used in PRODUCTION for mid C4's. This gasket also leaked. It was discontinued from SERVICE in March, 1988 and replaced by GM #14090908. The latter is very similar, if not identical, to it's predecessor.

The GM #14090908 was used through the remainder of C4 PRODUCTION (except LT5). It remains available from GM in SERVICE to this very day. When this gasket first came out I was kind of excited. Due to its rather sophisticated configuration, I figured that GM had finally come up with a gasket to "slay the dragon". I was wrong. This gasket leaked, too, even when replaced at every oil change.

For the C-5 to C-8 era LS and LT engines, GM went to a different design oil drain plug and associated gasket. This same system was used on many other GM cars, too, including one that I own. This system utilizes a different configuration oil drain plug with a "grooved" flange. A specially configured rubber gasket fits into the groove. The drain plug flange controls compression of the gasket to prevent any over-compression. When I first saw this on my car, I thought this has to be the "final answer". The drain plug was GM #24100042 and currently GM #11562588 with magnetic plug GM #88891787 (no longer available). The rubber gasket is GM #3536966. So, does this set-up finally "slay the dragon"? Nope! It leaks, too! 70 years of trying and they haven't got it right yet! By the way, these drain plugs cannot be retrofitted to earlier applications (not that anyone should want to) because they have 12 X 1.75 metric thread size.

Examples of the 14090908 and 88891787/3536966 are shown below:

DSCN4390.jpgDSCN4391.jpgDSCN4392.jpgDSCN4393.jpgDSCN4394.jpgDSCN4395.jpg

[Mark E.]

Re: C1 Oil Pan Drain Plug Gasket

Relying on the flange of the bolt as a seal doesn't seem to work. What if the drain hole had a threaded boss so the threads could also seal?

My wife's Jaguar XJ has the ultimate solution- no drain hole. For an oil change, it's pumped out from the filler hole. I'm envious- her car doesn't leak a drop of anything anywhere.

Rick,

Like most interesting threads, this one's discussion has naturally drifted a bit. Regarding your original post, my first thought was I wished my Corvettes were so perfect that I thought about a 30 mil difference in thckness of the drain plug washer.