Brake Proportioning Valve

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Nov 8, 2002 | 09:40 PM

jor

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Laughing Gas

Joined: Jan 2002

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From: Tucson

Brake Proportioning Valve

73 F-250 CrewCab
My son and I just did a brake job on his truck (shoes on back and pads on front) and an AutoZone master cylinder. We bled the new master cylinder and then bled the brakes the way I always have (into a glass jar until the bubbles are gone for each wheel). The brakes seem fine now but I got to reading an after-market repair manual tonight and it indicates I must push the rod in on the proportioning valve in order to get the brakes bled correctly. Is this good information? Thanks.
jor

Nov 8, 2002 | 09:49 PM

Mil1ion

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Brake Proportioning Valve

That doesn't make sense to me.

The Proportioning valve regulates how much fluid goes where.
Front to back.

The only rod it has is for the brake failure light that gets actuated.

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Nov 9, 2002 | 07:47 AM

jor

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Laughing Gas

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From: Tucson

Brake Proportioning Valve

Well, that's my opinion too but here's the quote from a Haynes manual: "On vehicles with disc brakes, a bleeder rod located on the pressure differential valve must be released to allow fluid to run to the front calipers." What do you make of that? Thanks.
jor

Nov 9, 2002 | 08:18 PM

Torque1st

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Brake Proportioning Valve

I have disk brakes on my F250 and I do not have a pressure differential valve. Just one line to the rear and another to a splitter for the front.

Do you have a differential valve in the line somewhere? If you don't I wouldn't worry. Some vehicles used to have a differential valve to activate the brake failure light and seal off the leaking half of the system. On those systems the valve would close during a brake bleeding job and they were hell to get centered again.

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Nov 10, 2002 | 09:44 AM

hawkrod

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From: Apple Valley CA USA

Brake Proportioning Valve

Nov 10, 2002 | 10:44 AM

74F1004x4

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Brake Proportioning Valve

The valve the book refers to is actually a combination of three things, proportioning valve, metering valve, and pressure differential switch.

The pin is on the metering valve. It takes something like 30psi to get fluid to flow through the metering valve. The master cylinder provides over 100psi. If you bleed the brakes by pumping the pedal you should not have to do anything with the pin. If you use a pressure bleeder you probably have to pull the pin out to get flow.

74F1004x4