I put in the new master cylinder and the brakes work great. The only thing is the top (2) holes in the cylinder did'nt match my original location but I guess that's fine. I'll just use some sheet metal screws to secure the top (2) holes.

58 Ford Custom 300 - San Pedro, CA (So-Cal)

I think a new master cylinder is the route I'm gonna go just to be safe. Thanks for all the help. I'll keep you posted.

58 Ford Custom 300 - San Pedro, CA (So-Cal)

I think you need either at least a kit but if it was me I would be buying a new master cylinder.When (or if) you replace it bench bleed it first before installing using a length of  brake  line and bend it so it is under fluid in the resovoir and pump it to recurculate fluid back into resovoir until there are no air bubbles.It works much better than trying to push air out through the whole system.Macs has the new master for $90.00(with cap).

  

You may have to remove the master cylinder and bench bleed it first. Sounds like pressure is getting past your seals in the master cylinder anyway. Probably time to put in a kit. If pressure gets by the seals it could cause brake fluid to back up into the fill area and leak out. See attached picture. Chuck in NH

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Well, the original cap was leaking so when I bled the brakes it would only last a few days then I would get a lot of air in the system and I would have to rebleed. Now that I have a new cap it does'nt leak but I can't seem to get any 'feel' on the brake pedal, it just goes straight to the floor. The master cylinder is full, I tried bleeding the brakes but the pedal still goes to the floor and the master cylinder is still full. What could it be other than the master cylinder itself? Before it would go to the floor but then I would keep pumping until it 'catches' now I don't get anything when I press the pedal.

58 Ford Custom 300 - San Pedro, CA (So-Cal)

What was the original reason for changing the cap?

  

I can't figure this thing out. I have tried to bleed the brakes with no luck. Could my master cylinder be bad?

58 Ford Custom 300 - San Pedro, CA (So-Cal)

If not overfull could one of the rubber cups in the cylinder be letting pressure back into the fluid area? Chuck in NH

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Here's the one I bought from Mac's Antique:

58 Ford Custom 300 - San Pedro, CA (So-Cal)

Hi Paul.You are correct about no vents.I just remembered the one that was on mine originally was a solid cap.If you look at Ebay item # 190437936565 you can see its solid.Even the replacement dual master on mine now has the solid steel clip-on cap with a rubber seal under it and no vents.