Master Cylinder Cap Gasket

[macblazer]

Anyone have any clue where the heck you can find a replacement gasket for the master cylinder cap?

I've got a 1971 Chevy C20 Longbed and I'm having a royal pain of a time finding one that will match.

[WarMonger]

Do you have a pic of what you need? I just replaced my Master cylinder and I have my old one. Nothing wrong with the gasket or top cover.

[macblazer]

Originally Posted by WarMonger

Do you have a pic of what you need? I just replaced my Master cylinder and I have my old one. Nothing wrong with the gasket or top cover.

See the pictures attached

[macblazer]

Originally Posted by macblazer

See the pictures attached

Basically the rubber gasket seems to be worn out and doesn't seal tight anymore so fluid leaks out from time to time. I've tried a bunch of different places and have yet to find a place that sells just the gasket. Don't really want to replace the entire master cylinder just because of a bad cap gasket.

[johnmiller66]

If you find one please post where you got it. I just put a new booster and master cylinder on mine. It leaks like crazy out the cap. The top of the master is beat to hell and won't seal properly. I don't really want to change out the master but I might have to. I should of looked over the Oreilys crap before I installed it.

[macblazer]

Originally Posted by johnmiller66

If you find one please post where you got it. I just put a new booster and master cylinder on mine. It leaks like crazy out the cap. The top of the master is beat to hell and won't seal properly. I don't really want to change out the master but I might have to. I should of looked over the Oreilys crap before I installed it.

Yeah if I can't find a replacement gasket I might just have to replace the master cylinder as well.

Didn't have this problem with my 72 because with that one I had the entire brake system replaced except for the lines back when I got it. So I guess I didn't realize finding this rubber gasket would be this much of a pain in the ass.

[Andy4639]

Have either of you tried pushing out the cap further on the lid. Take the gasket out and punch the lids out as much as possible. This will in turn make the lid fit tighter when you pull the bars over it. You may want to clean the edges of the master cylinder also.

Quick google came up with plenty of them.
Advance Auto




Summit

http://www.summitracing.com/parts/rn...lM4aAgWf8P8HAQ

[macblazer]

Originally Posted by Andy4639

Have either of you tried pushing out the cap further on the lid. Take the gasket out and punch the lids out as much as possible. This will in turn make the lid fit tighter when you pull the bars over it. You may want to clean the edges of the master cylinder also.

Quick google came up with plenty of them.
Advance Auto




Summit

http://www.summitracing.com/parts/rn...lM4aAgWf8P8HAQ

Actually talked to Advance Auto today and gave them the year/make/model and they don't have it. They have ones that look like it, but nothing that supposedly fits this one.

I even tried putting some extra rubber under the gasket to try and build it up for a tighter seal. But might order one of these to see if I can make it work and if not, pull the seal, put some silicon under it, let that harden a bit and put the gasket back in to see if I can build it up more for a tighter seal.

[Aruba1]

Can you post a picture of the master cylinder itself? From the upper picture it seems like what you have is a C10 master cylinder. Maybe that is your problem but I believe (someone correct me) that the caps are the same. Here are some pics of C10 vs C20 MC. http://67-72chevytrucks.com/vboard/s...d.php?t=666291

[Shell]

Dorman p/n 42071. NAPA or any of the parts should be able to get them.

[macblazer]

Originally Posted by Aruba1

Can you post a picture of the master cylinder itself? From the upper picture it seems like what you have is a C10 master cylinder. Maybe that is your problem but I believe (someone correct me) that the caps are the same. Here are some pics of C10 vs C20 MC. http://67-72chevytrucks.com/vboard/s...d.php?t=666291

Maybe....I can actually check that. I have a 1972 C10 in the driveway right in front of this 71 C20.

[Andy4639]

They advertise it. I would try talking to some one else about it.
Just for reference I was going by the picture posted.
The C/20 maybe different.


http://www.dormanproducts.com/c-504-...r-gaskets.aspx

[Shell]

The P/N I posted is for the C10

[macblazer]

Originally Posted by Shell

The P/N I posted is for the C10

I'll check the master cylinder on my 72 C10 tomorrow and see if it matches the one on the 71 C20. If so I'll just order the C10 one posted above. Thanks for all the ideas guys!

This truck was sitting for probably 6-9 months when I bought it so I've been replacing a lot of rubber parts and such to take care of minor leaks here and there.

[EARNHARDT#3]

http://pages.ebay.com/link/?nav=item...d=111175679004

[Aruba1]

Any update?

[macblazer]

Ordered one and waiting for it to show up. So we'll see when it arrives.

[johnmiller66]

Hears a pic of my master cylinder and the new gasket advance auto ordered for me. It's about an inch to small in length and about a half an inch to narrow.

[johnmiller66]

Master

[macblazer]

Originally Posted by johnmiller66

Master

Looks like about the same one I have.

[RichardJ]

If the cap is bent, you should probably replace it, even if it's just one from a wrecking yard. The problem isn't so much as it leaking fluid, the problem is in allow any air to enter. Humidity in the air is easily absorbed by brake fluid, contaminating the fluid and causing corrosion.

[macblazer]

Ordered this one:

Description SKU
MOTORMITE BRAKE MASTER CYLINDER CAP GASKET 42071 MM42071.1764

Ordered it from carpartkings.com and it looks like it might be a fraction of an inch smaller on the sides, but still looks like it fits in all the areas it needs to. I sprayed down the master cylinder down with brake cleaner so we'll see if we get any more leaks, but so far so good. I think it was about $9.00 with shipping and everything.

[EARNHARDT#3]

Originally Posted by macblazer

Ordered this one:

Description SKU
MOTORMITE BRAKE MASTER CYLINDER CAP GASKET 42071 MM42071.1764

Ordered it from carpartkings.com and it looks like it might be a fraction of an inch smaller on the sides, but still looks like it fits in all the areas it needs to. I sprayed down the master cylinder down with brake cleaner so we'll see if we get any more leaks, but so far so good. I think it was about $9.00 with shipping and everything.

That's the exact one I posted above for you. If you look the ebay seller is carpartkings.

[MagmaJct]

I recently had to replace mine. This diaphragm prevents moisture in the air from contaminating the fluid. It allows for a partial vacuum that may occur as the fluid is "consumed". (A small amount of fluid always leaks past the seals in the calipers and wheel cylinders and must be made up.)

I got mine from O'Reilly's, but I had to go to a hub store. I tried to look it up on their site so I can just paste the link here. But their stupid site wants me to enter the specifics of my vehicle. When I did that, it "found nothing". I know they have it, but I doubt it's in their database for working with our trucks.

Regards,
Mike

[70's luvr]

I bought a replacement and just stacked it on top of original. Obviously harder to lock cap down but no more leaks.