Thread: Low Power brake booster vacum

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Jim, the centering of the proportioning valve that It1s10 mentioned is for the brake warning light, that you don't have connected. That's the terminal in the middle of your proportioning valve. Check to see if you have a connection to ground at this terminal. If you have a ground connection here, your warning sensor has been activated, and the internal piston will need to be re-centered to turn off the warning sensor. Since you have such a drastic difference in your front-to-rear brakes, this has probably been activated. To centralize this valve, you'll need to create a difference in the pressures between the front and the rear brake circuits that is the opposite of what caused the activation of this valve. If this is necessary, watch your ohm meter or test light while you bleed the front brakes until the switch turns off. Now try your wheel-spinning brake test again.

This type of proportioning valve is non-adjustable. Are you sure it's calibrated properly for your brake system? What do the people say where you bought it? Have they tried to help you solve your problem? Your major problem is the balance of the brakes between the front and rear brake circuits. That's what the proportioning valve is supposed to do! Any changes to the size of your booster won't fix that.

Your rear brakes must not be seized up, or the rear brakes would not release when you take your foot off the pedal, so they must not be getting sufficient pressure. The craftsmanship of your car is so nice, I can't imagine a pinched or crushed brake line, and this would also cause your rear brakes to drag when you take your foot off the pedal. (The rear brakes do release promptly when you take your foot off the pedal, don't they?) This points to a bad m/c or a bad proportioning valve.

Is there another port on the bottom of the proportioning valve with a plug in it? The proportioning valves I'm familiar with have the rear brake line connected to the bottom of the valve, rather than the back, like yours.

By the way, your front reservoir IS larger than the rear reservoir. Look at the bulges in the sides of the casting around the front reservoir.

Roy, I'm not sure what you mean buy is the proportioning valve calibrated for my brake system ??. I cannot ask the people I bought the brake system from because I bought the booster and master from Eklers and the Proportioning valve from Fatrodder on ebay, I probably should have bought a complete setup.
I rechecked all my brake lines (Checked good) and rechecked my rear brakes to make sure I assembled correctly All tooked good.
I checked to see if the warning sensor had be activated with my ohm meter and it was not activated. I tested it when I rebleed the brake system again.
Just a note: If you look at the Picture of the engine compartment you will see the vacum canister with a guage on it. When I stop the engine the vacum will hold at 17 for 20 minutes.

I know what the article abour residual valves says in MP but you have to read alot more than one article and get the big picture. My blown 32 has no residual valves runs a cool 550 h.p. has 18 in. LIVE vac. and the master is even under the floor and the brakes are perfect. Hum! Oh whoa is me. Why does my car stop so well? could it be because I have read the book on brake systems. I don't mean to be a smarty pants Mr. Techinspector But I do know brakes and MP is the best in the business and with their tech information in their book you can't go wrong. You just got to read it all not just part of it.