FYI FORD MustangSteve's Ford Mustang Forum / proportioning valve with all drum brakes

**Posted by swolfert84** 9/22/2017 8:52 AM

I have a 65 mustang with DRUM/DRUM none power brakes. It has a single MC that runs into what i look call a Proportioning valve and then to each from and the rear drums share a line which is T off in the back.
Engine is the 289

The rear brakes are locking up driving down the road and then the entire car stops.

What should i do to correct this issue and how to do it without converting to disc.

Last edited by swolfert84 (9/22/2017 8:52 AM)

**Posted by TimC** 9/22/2017 10:04 AM

First & foremost: Welcome to FYI Ford!
Second: You placed your post in the "tips & How to's section of the Forum. You will get more attention, if your questions are asked in the "technical discussions" part of the forum.
Third: Assuming that your parking brake is functional, and properly adjusted, your brake issue may well be related to the flexible brake line that goes up and over the rear axle. When those hoses get old, the inside of the hose deteriorates, and the inside collapses and restricts the flow of brake fluid. It may look perfect on the outside, and be junk on the inside. What may be happening is, when you push on the brake pedal, it properly forces brake fluid to the rear brakes, and applies the rear brakes, but when you take your foot off the brake pedal, the restriction in the bad hose restricts the flow of fluid back to the master cylinder reservoir. Due to the restriction, the rear brakes stay engaged.
Replace the hose, and bleed the rear brakes. It's cheap, and if you don't know its age & condition, it's probably time to change it, anyway.
Hopefully others will chime in.

**Posted by Alessandro** 9/22/2017 10:07 AM

Hi , if is the oem proportional valve could be not working properly after all these years .
I dont believe you could repair , simply put it new .
Maybe you should check also the distance adjuster of drum shoe if works .
You can check the front line pressure and back and see how much difference ,
Or simply you could have some clogged hose that happens when have old Rubber hose and old oil.
I will check all if talking on brakes

**Posted by 50vert** 9/22/2017 10:16 AM

Welcome to the best place around. You will get more responses if you post this in the tech section.
My WAG without further information, is a broken spring in one of the rear brakes. pull the drums off and see what you can see.

**Posted by MS** 9/22/2017 2:36 PM

There is no proportioning valve on a 65 drum brake Mustang. It is simply a brass block where all brake lines come together.
If rear brakes are locking up, it is probably one of two things:
1. Old rubber brake lines are swollen internally, cutting off return flow. (see pic)
2. Grease from leaking rear bearing have contaminated the brake shoes. I never have figured out how good old slippery grease makes the brakes lock up, but it sure will do it if it gets on the brake shoes.