The Ford Barn

pete rose · 06-30-2025, 08:01 PM

Hi Guys
I'm on my second master cyliner due to the first one leaking
at both ends. The second one has no leaks but has an issue that I need help with. when I drive the car I need to use the brakes to stop the car on a hill
by my neighborhood at a light. then there is another light a short distance away
followed by another stop sign.After pumping the breaks to make these stops the brake pedal gets harder and harder till the brakes are almost locked on..
Anyone had this problem and know a cure? do I need a better Master cylinder?
It seems like the internal residual valve is working incorrectly..
Need suggestions for a made in America master cylinder or any other suggestions the Barn experts can offer me
Thank you, all help appreciated as usual
Pete

Bob C · 06-30-2025, 09:00 PM

Maybe not enough free play in the master cylinder push rod.

alchemy · 06-30-2025, 09:09 PM

There should be a 1/16” of free play in the pedal before it engages the master cylinder. Get on the floor and push the pedal with your hand to feel that you have this slight space before it hits.

And, you do have a spring that pulls the pedal up to the floorboard upon removal of your foot, right?

Flathead Fever · 07-01-2025, 12:33 AM

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Usually like others have said, the master cylinder will lock up if there is freeplay in it. As soon as you step on the brakes the piston moves forward and covers the return port up so the master cylinder can build up pressure. That orifice remains covered until the piston returns all the way back. If you don't have just a lttle play in the rod the fluid cannot return/ This only take one or two pumps of the pedal and the brakes will be locked up. They will not unlock until you open up a bleeder and let some fluid out but then it would just lock up again with a couple of pumps. I'm not sure if this is your problem or not because you didnm't mentiion having to release the pressure to get it to release.

06-30-2025, 08:01 PM	#1
pete rose Junior Member Join Date: Jul 2018 Location: langley bc canada Posts: 25	42 brake master cylinder on a 37 Hi Guys I'm on my second master cyliner due to the first one leaking at both ends. The second one has no leaks but has an issue that I need help with. when I drive the car I need to use the brakes to stop the car on a hill by my neighborhood at a light. then there is another light a short distance away followed by another stop sign.After pumping the breaks to make these stops the brake pedal gets harder and harder till the brakes are almost locked on.. Anyone had this problem and know a cure? do I need a better Master cylinder? It seems like the internal residual valve is working incorrectly.. Need suggestions for a made in America master cylinder or any other suggestions the Barn experts can offer me Thank you, all help appreciated as usual Pete

06-30-2025, 09:00 PM	#2
Bob C Senior Member Join Date: May 2010 Location: So Cal Posts: 9,356	Re: 42 brake master cylinder on a 37 Maybe not enough free play in the master cylinder push rod.

06-30-2025, 09:09 PM	#3
alchemy Senior Member Join Date: May 2010 Location: middle of Iowa Posts: 889	Re: 42 brake master cylinder on a 37 There should be a 1/16” of free play in the pedal before it engages the master cylinder. Get on the floor and push the pedal with your hand to feel that you have this slight space before it hits. And, you do have a spring that pulls the pedal up to the floorboard upon removal of your foot, right?

07-01-2025, 12:33 AM	#4
Flathead Fever Senior Member Join Date: May 2010 Location: Yucaipa, CA Posts: 1,358	Re: 42 brake master cylinder on a 37 Sponsored Links (Register now to hide all advertisements) Usually like others have said, the master cylinder will lock up if there is freeplay in it. As soon as you step on the brakes the piston moves forward and covers the return port up so the master cylinder can build up pressure. That orifice remains covered until the piston returns all the way back. If you don't have just a lttle play in the rod the fluid cannot return/ This only take one or two pumps of the pedal and the brakes will be locked up. They will not unlock until you open up a bleeder and let some fluid out but then it would just lock up again with a couple of pumps. I'm not sure if this is your problem or not because you didnm't mentiion having to release the pressure to get it to release.