Master cylinder “seapage”

[74bronk]

I have installed a power brake front disc conversion system since 2006 from wild horses. I’ve replaced the master cylinder once since then same reason “seapage”. Vehicle does sit a lot. Ever since I’ve owned it the master cylinder “seaps break fluid” breaks work decent nothing spongey about them. Also noticed it seems like the breaks stay pushed onto rotor or drums when foot off pedal. Excess drag. (Wonder if related”) possibly the brake distribution valve? Any help appreciated on issues I’m having

Fyi I currently have a 1974 bronco if that helps..

 

[Timmy390]

MC's shouldn't leak. Where is it leaking from? Guessing the back where the pushrod goes in? How does the fluid look in the MC? Is it brown, yellow or black?

Brakes dragging......What MC are you using? You mentioned you replaces it. If you replaced it with a stock 74 drum/drum, my guess is the MC came with residual pressure valves. To use this MC with disc brakes you need to remove the RPV from the port going to the front brakes. The RPV was used on all drum brakes to keep the springs in the shoes from pushing all the fluid in the wheel cylinders back to the MC. They hold 7-10 pounds of pressure on the drum brakes.
https://classicbroncos.com/forums/threads/residual-pressure-valve-removal.85818/

I've found some replacement MC's have them and some don't. My last one had them.

Tim

 

[74bronk]

MC's shouldn't leak. Where is it leaking from? Guessing the back where the pushrod goes in? How does the fluid look in the MC? Is it brown, yellow or black?

Brakes dragging......What MC are you using? You mentioned you replaces it. If you replaced it with a stock 74 drum/drum, my guess is the MC came with residual pressure valves. To use this MC with disc brakes you need to remove the RPV from the port going to the front brakes. The RPV was used on all drum brakes to keep the springs in the shoes from pushing all the fluid in the wheel cylinders back to the MC. They hold 7-10 pounds of pressure on the drum brakes.
https://classicbroncos.com/forums/threads/residual-pressure-valve-removal.85818/

I've found some replacement MC's have them and some don't. My last one had them.

Tim

Yes look like it’s leaking from the rear . When I replaced MC I called WH they gave me a part number to buy from Napa . I assume it’s for a Chevy front disc set up

 

[Apogee]

What's the Napa part number? Several auto parts stores offer lifetime replacement on their "new" casting master cylinders, so that might be something to consider. That said, master cylinders shouldn't leak at all, and if your brakes are showing signs of excessive drag, that deserves further attention.

 

[Timmy390]

I would double check the MC for the valve. Stick a metal pick the ports. Metal no RPV, rubber means it's there.

Back to the fluid question...If it sits allot brake fluid can contaminate quick with moisture. The fluid in my Mach 1 was black when I checked it a few weeks back. The contamination can build up like a "crust" on the internal rubber seals in the MC causing leaks. Had this on my samurai when I got it. Cleaned the crust off and leak stopped.

Change out the MC under warranty, replace all the fluid i/e/ bleed the system well and drive it more

Tim

 

[74bronk]

What if the lines were crossed on the proportion valve coming from the master cylinder would it cause the caliper to push against the rotor?