The Stovebolt Site Forums The Parking Lot Big Bolts Brake master cylinder cover

Is there a source for a socket that fits the cover on the brake master cylinder on a 1950 GMC 453 truck? It’s a square nut on top. Haven’t measured size yet. Started to get back to work on my Old Firetrucks and need to check fluid level. It’s on tight. Thanks

If you've got a welder it wouldn't be hard to make a wrench to fit the square nut. It would just take a couple lugs welded to a flat bar and a socket welded in the center. I made a tool like that for the steering gear bearing adjusting plug jam nut, which was way bigger than any of my sockets.

Thats probably what I’ll end up doing..hit the pawn shop for a big socket to weld to.

Measure the square and then do a search for an eight point socket that size. Eight point sockets are for square nuts and bolts.

eagleuh1 Here in the corn belt have learned to make square drive sockets out of wore-out disc bearing inner races,they are hard anneal them weld on whatever is needed to drive it. Or torch out a square drive piece of plate weld on a driver. By chance found a tee handle driver that fits the hex ones,hard to hurt it thru that floor board hole !! Also might use 3/4 or 1 inch drive socket turned the other way to shake it loose,

a 3/4 wrench fits the nut I have 1 with the box end opened and put that on the nut with another wrench thru the box end like a t works every time

hippydave I've done that it works,worst thing is a plastic one.

I found the right tool, unfortunately it rounded off the cap square without loosening it. My master is leaking apparently at the fittings , so I’ll probably just replace if I can find one. I can’t see a number on the in place master, just Wagner Lockheed on inner side. Can’t see outboard side of master. Would anyone know of a source for the master cylinder for a 3 ton 1950 GMC 453 truck.

Hy eagleuh1, according to my brake parts catalogue the master cylinder for your truck has a 1.5" bore, the Raybestos p/n for that master cylinder is MC13066. I checked RockAuto for that p/n, no parts found. Good luck with your search.

There are companies that can sleeve your existing MC and rebuild it to new, like White Post Restorations in Virginia.

Mike B

That plug is most likely die cast ("pot metal") Use a hammer and punch to break it up, clean out the pieces, and replace it with a rubber expansion freeze plug with a tiny vent hole drilled through the center bolt. Problem solved!
Jerry

Thanks, probably what I’ll do this weekend. Still looking for a replacement Master or rebuild kit. Gonna try and get mirror in to look for number on frame side . Don’t want to take off if can’t get kit for it.

We usually rebuilt master cylinders "in place" by removing one or both end caps and replacing the pistons and seals. If the area of the cylinder where the piston travels isn't rust pitted, there's really no reason to remove it from the frame. I've even honed a few of them "in place", although cleanup of the abrasive residue from the hone can be a challenge.
Jerry

eagleuh1,

Just a note that while searching for other parts/things, came across this eBay ad for a correct 1-1/2" diameter bore master cylinder rebuild kit in case the cylinder you have is still rebuildable.

Let us know about the casting number if you can read it and good luck on getting the brakes fixed up.

Dan

Jim Carter says they have it, but says the bore is 1 1/4" ... https://oldchevytrucks.com/me166.html