Master Cylinder Gasket & Gas Tank

[Don Schuette]

In my 68 Assembly Instruction Manual, it shows a gasket between the master cylinder and the power brake booster. However, GM, FELPRO, nor Mr. Gasket show or stock a gasket. When I took the old master cylinder out, I do remember a paper gasket of some sort that vaporized on removal. Does anyone know if this gasket should exist and/or who stocks it?

Also, after 21 years of storage, it appears all the gas either evaporated or leaked out the rubber fuel lines (which I will replace). However, there are various small (individually the size of a thumb) rust puddles where the last amount of gas puddled up in between the ribs in the tank and are a little crusty. Any ideas to cleaning out these rust puddles without removing the tank? The rest of the tank looks shiny new on the inside.

Thanks in advance.

Don Schuette #32294

[Jim T.]

Re: Master Cylinder Gasket & Gas Tank

If you had some gasket material, you could make your own gasket real easy. I don't know if you can still buy it from parts stores or not. Many years ago I purchased a roll and have used it on occasion. Using a ball-peen hammer you can tap the edges and get a pretty good cut of gasket when it is placed on the master cylinder. Your gas tank is easy to get into. Remove the gas lid bezel, gas cap, and then remove the rubber protector that funnels water into a drain hose. Now just remove the bolts that holds the gas filler and unless your arms are really big, you should be able to access these puddles of rust and clean it out. You should get a new gasket for your gas filler. The one on your 68 is cork, I don't know if they are available from GM or not. I bought a stash of them years ago for my 68 and 70.

[Joe L.]

Re: Master Cylinder Gasket & Gas Tank

Don-----

The part that you seek was GM #730392. However, it has been discontinued for quite some time. Incredibly, I don't know that anyone reproduces this part. I would have expected that if anyone reproduced this part it would be the "King of Gaskets"----Dr. Rebuild. However, he doesn't show this one in his catalog. It must be the ONLY gasket that he doesn't have available. Since it was, apparently, just a round, paper gasket, you should be able to make one up rather easily from a sheet of gasket material.

As far as the rust in the tank goes, you might be able to clean it up by sticking your hand down into the gasoline tank (after removing the filler neck) and working on it with "Scotch-Brite". This assumes, of course, that you have relatively small hands (or can enlist the assistance of someone that does) and the corrosion is not too extensive and deep. The Scotch-Brite will create no sparks, so there should be no danger.

[Joe L.]

Re: Master Cylinder Gasket & Gas Tank

Jim----

The GM gasket was GM #3826417, but it's been discontinued. Dr. Rebuild carries this gasket in the original cork material. But, you can do better. Get a sheet of Buna-N gasket material from an industrial supplier and make a gasket. The cork ones deteriorate over time (often causing a very small leakage of fuel, the vapors of which can permeate the cockpit but be devilishly difficult to locate), but the Buna-N one is FOREVER. I've been "down this road".

[Jim T.]

Re: Master Cylinder Gasket & Gas Tank

Thanks Joe for the tip on the Buna-N gasket material. Will have to do a local search and see if anyone in town carries it.

[Frederic Lynes]

Re: Master Cylinder Gasket & Gas Tank

Don,

I own a 1979 L-82. When I decided to replace all of my brake parts, I took out the master cylinder and found an old rubber gasket, approximately 1/4 inch thick in between the master cylinder and the booster. The gasket was completely dried up, so I tossed it. There was also a round piece of flex metal, I'm assuming, to keep the rubber gasket in place. My father in law was the original owner of the car and had never had any work done on that part of the car, so that gasket was original. Anyway, to make a long story short, I chucked the rubber gasket, replaced the master cylinder and, as a result, my brakes would continuously go soft, after three days, even with pressure bleeding. It was through sheer luck that I found a 1982 Crossfire Injection with the same set up, so I took that rubber gasket, which was still intact, and I put it on mine. I bled the brakes and have not had a problem since. I never did see a paper gasket, though. Hope that helps you a bit. I don't how different your set up is from mine. Regards, Fred