Brake Valves for Dummy Mechanics

An adjustable brake proportioning valve

We have a lot of DIY types on staff. Several have worked on their vehicles – doing oil changes and tuneups; replacing water pumps, alternators, distributors; one has even done some brake work. But not a one of them would ever let the likes of Dianne Hermance (aka Dianne Christensen-Hermance) anywhere near their brakes. That's because the team members read through what she told people at eHow.com (and then ItStillRuns.com) about "How to Reset a Brake Proportioning Valve."

Don't know what a brake proportioning valve is? well, neither did any of us, so we did some research (something Hermance should have done a better job of). "All" the valve does is regulate the fluid pressure in the brake lines of certain vehicles. It's especially necessary in cars with rear drum brakes and front disc brakes to prevent the rear brakes from locking before the front brakes engage. Dianne's version of this definition is,

"A brake proportioning valve is typically located in the rear brake line and enables you to adjust the rate of pressure increase to the rear brakes. It changes the proportion of brake fluid."

In the real world, 1) the valve is often part of the master cylinder, 2) in general, only performance versions are adjustable, and 3) it doesn't change the "proportion of brake fluid," it changes the pressure in the fluid. Hermance did a quick google search and came up with a performance parts website; after which she apparently made up some "instructions" out of whole cloth, claiming they were from a book in the "for Dummies" series. Her "instructions" claim that there is a reset button on the valve, which you must find by jacking up the car.

One of Hermance's more inane instructions is,

"Locate the brake proportioning valve near the rear brake line."

"Near" the brake line? How does it do its proportioning thing if it's merely "near" a brake line? and then there's this:

"Push the reset button located on the valve with your fingers, which will reset it so the valve is working properly again."

Duh. Even the adjustable proportioning valve Dianne thinks is representative doesn't have a "reset" button. Perhaps she's confused about what a bleeder button does, since reset buttons are pretty unlikely on a mechanical part like a proportioning valve. According to the gearheads out on the 'net, proportioning valves can get stuck and need to be replaced. Sometimes you can unstick one by tapping on it with the handle of a screwdriver, but that's a kluge. Replace the thing: they're only a few tens of dollars!

Whatever you do, though, don't look to the likes of Dianne Hermance for instructions in how to replace or repair anything that has to do with your brakes; not if you value your continued existence. Come to think of it, you probably want to ignore anything our Dumbass of the Day writes about cars (or carpentry) at all.

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