faq

The cast iron Kelsey-Hayes combination valves used on many vehicles made during the 1970s contains three components: a proportioning valve, a pressure differential switch, and a metering valve. Consequently, we have a kit for each of the components found inside the most common valves:

Kelsey-Hayes Iron Combination Proportioning Valve Kit

Kelsey-Hayes Iron Combination Pressure Differential Switch Kit

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A metering valve (sometimes also called a hold-off valve) is designed to engage the rear brakes just before the front brakes on cars equipped with front disk brakes and rear drum brakes. It does this using a combination of springs, seals, and pistons to restrict fluid flow to the front brakes until a relatively low fixed threshold pressure is reached. Forcing the rear brakes to engage prior to the front brakes is supposed to enhance braking stability.

A proportioning valve is used to reduce the amount of brake fluid pressure applied to the rear brakes. They are often (but not exclusively) found on cars equipped with front disk and rear drum brakes, and are not typically found on cars equipped with four-wheel drum brakes. The valve assembly contains a combination of seals, pistons, and springs that work together to reduce the pressure of fluid passing through the valve.

A pressure differential switch (sometimes also called a distribution block or tee) is designed to detect a difference in brake system pressure between the front and rear portions of the braking system on a car equipped with a dual master cylinder. The switch assembly contains a sealed piston (or pistons), an electrical terminal, and sometimes springs. The piston moves from a centered position when the fluid pressure on one side of the piston is higher than the other, usually as a result of a fluid leak.

Sorry, but I don't offer a general valve rebuilding service. The only valves I'm interesting in rebuilding are those that aren't yet listed in my catalog. Please contact me if you have an unlisted valve and you're interested in having it rebuilt. I'll let you know if I can help you. Please have a picture or two handy.

I currently offer brake valve rebuild kits for a limited number of vehicles. My catalog is structured by model year and valve type. Kits for cars originally equipped with 4-wheel drum brakes are identified as a "Drum Brake Pressure Differential Valve Kit". Other kits are used for cars equipped with front disk and rear drum brakes. If you're not sure of the type of valve you have just read the description for the kits that are appropriate for your model year - the description includes a list of vehicles for which the kit has been confirmed to be appropriate.

The brake system warning light is illuminated when the pressure between the front and rear parts of your braking system are unequal, which causes a piston inside the pressure differential valve to move off-center. When the piston moves it makes contact with an electrical switch, which completes a circuit and illuminates the dash light. A difference in pressure can exist while bleeding the brakes or as a result of a fluid leak.