1952 Hard Brakes - Brake light stays on

[jplutz]

Greetings, I have had the following problems since I purchased the car in 2021. The previous owner has sadly passed away. I have installed new front wheel cylinders, shoes and springs, and a new master cyl and bled the front system. I also changed brake light switches 5 times, finally putting in a Harley C switch. Every time I re!ease fluid pressure, the pedal goes down an inch or 2, but after driving a mile or so, the pedal is at the top and hard and the brake light is on. I just put it up on blocks and checked the rear brakes and they look good. It needs rear park brake cables.
I also need new front drums, but only see them at Kanter Auto Parts.
Any help would be appreciated.

[Mart]

It sounds like your master cylinder push rod is too long and not allowing the recuperation port to work properly. Try shortening the push rod a little bit. The pedal might have an eccentric bolt that could be adjusted.

[38 coupe]

What condition are the brake hoses? Hoses that are collapsing internally can act like one way valves and hold pressure. Frequently replacing the rear hose gets skipped when doing a brake job, sometime with bad results.

[Bill OH]

I had brakes hang on on a 78 Ford PU. Removed master cyl, measured the piston distance to mounting surface and the length of rod to mounting surface - rod too long. Shortened the rod and problem fixed. You have done much on your brakes and I would replace the 3 hoses and emergency brake cables. Then you have covered all the bases. Brakes and tires have a high priority.

[Mart]

A collapsed hose can make a wheel bind, but would not make the brake light stay on.

[Ggmac]

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Check adjustment of master cyl push rod as said earlier. Need some play between the mstr and pedal

[jplutz]

Thanks for the advice.
When my friend and I replaced the master cyl we had a lot of trouble reattaching the rod to the pedal. I had to remove the rubber stop under the dash to make room for the rod to attach to the pedal post. And, the eccentric screw didn't adjust enough to make a difference. Is this a rod length problem or do I have the wrong cyl attached?
Also, regarding the hoses, I installed new hoses and wheel cyl on both front brakes. And the solid front cross over line was replaced with a new copper alloy line because the old line was leaking at the right side fitting. This was an old leak as the frame and suspension are covered in crud. The leaks are fixed.
I have a new line for the rear that I have not installed yet.
Regarding the Master cyl, I purchased a generic one that supposedly fits many cars of that era. Could it be that I need a specific one for a Ford?
Again, Thank You All for your input.

[Mart]

For ease of fitment and purely for testing, You could try undoing the master cylinder and packing it out with a couple of washers under each bolt. If the brakes work ok you could try one washer in each position. If the brakes work ok you then know you can either leave it like it is or shorten the pushrod by the thickness of one washer. Can you not use the pushrod from the old cylinder?

You need to establish a pathway to get the info you need.

Having to remove the pedal stop and the eccentric bolt not being in range would definitely point to the pushrod being over length.

Mart.

[aussie merc]

if you had trouble refitting the master my guess is that its wrong and this would give you no end of problems . If you still have the one you removed i would get it rebuilt and then refit also if you don't know how old the hoses are i would replace them as a general rule of thumb is replace every ten years regardless [cheap insurance]

[jplutz]

I am using the original pushrod. The old cyl had the same problem, that is why I changed it. I will try the washer trick to see if that makes a difference.
Thanks.

[Wayne Schuenke]

Make sure the vent is open on the cap

[51504bat]

When I bought my '39 p/u it did the exact same thing. The PO had redone the brakes and installed an off shore M/C. I replaced it with a USA made Wagner I got from Joe's Antique Auto. Problem solved.

[5851a]

Someone a short time back mentioned Mustang brake drums fitting a 54, maybe the same? I looked but couldn't find info.