Thread: Brake problems on my 48 Plymouth

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Thanks, I don't have a proportioning valve, system is all still stock, but I will try your process of elimination idea. That does seem to be the best way to confirm the bad master cylinder, before removing it.

Thanks again,
Tim

Look inside your master cylinder. There should be 2 small holes in the bottom of the reservoir. 1 is the supply to the piston and the other allows the brake fluid to bleed back into the reservoir when you take your foot off the brakes. If they get restricted they can keep your brakes locked up.

Sounds like the pushrod is too long, not letting the piston return fully. If that happens, the return passage won't be opened, causing pressure to be retained in the lines. Some kits have deeper rubbers than original, causing that problem. Is there an adjusting system on the rod? I haven't worked on old Mopar brakes in decades, but most cylinders have some sort of adjustment.

Thanks to both of you for the tips, this is my first time back on the site since new years eve. I will check the master tomorrow to make sure the return hole is free or the cups are returning far enough.

Thanks again,
Tim

Let us know how it comes out.