what is the purpose of the proportioning valve?

15

Asked by Dec 15, 2015 at 07:51 PM about the 2000 Chevrolet S-10

Question type: Maintenance & Repair

I have installed the booster and master cylinder from a 2000 S-10 in my 1952 CHEVY. RESTORATION. I did not install the proportioning valve. I have run the lines directly from the master to the front and rear brakes..I am unable to get any brake pedal in spite of repeatedly bleeding the system.
Is the proportioning valve required? Are there other items needed in the system?

9 Answers

11,105

Proportioning valve is to limit the brake pressure in the rear brakes during a panic stop: http://www.freeasestudyguides.com/proportioning-valve-diagnosis.html

1 out of 1 people think this is helpful.
69,495

In other word yes, it would be a good idea to have it, or your rear breaks will be locking up all the time. Brake pedal low? 2 things to check. The rear breaks need to be adjusted up to the drums so as they drag a bit, so the wheel is not free wheeling when you spin it. Then did you bench bleed the master cylinder before putting it on?

69,495

In other words yes, it would be a good idea to have it, or your rear wheels will be locking up on harder breaking. Break pedal low? 2 things to check, the rear break shoes need to be adjusted up to the drums so as the wheel is not free wheeling when you spin it, they should drag a bit. And then did you bench bleed the master cylinder before putting it on?

1 out of 1 people think this is helpful.
15

OK I understand this. Is the lack of the proportioning valve keeping me from building pressure in the entire system? I have bleed the system and have fluid in all the lines and the wheel cylinders but cannot get any pressure built up. Pumping the pedal does not result in fluid discharge from the bleeders. I am a seasoned amateur mechanic and I am stumped.

69,495

Did you bench bleed the master cylinder before putting it on? Also the rear break shoes need to be adjusted up to the drums so they drag a bit.

1 out of 1 people think this is helpful.
15

Yeah I did bleed the master. The rear shoes do need adjusting. I'll try this and install the proportioning valve. Maybe this will help. Anyway thanks for your interest and help.

65,905

Your '52 had a single reservoir system while the '00 has a dual reservoir (required 1967 and forward). A proportioning valve regulates the front to rear pressures for even braking on a disc brake system. You may do better with a late '60s GM master cylinder if you still have drums all around. The chamber for the front half of the braking system on a disc brake set up is larger than the chamber for the rear half. At least it's supposed to be. On a 4 wheel drum set up both chambers are the same size. HTH. -Jim

1 out of 1 people think this is helpful.
Best Answer
15

Still messing with this problem. I have discs on the front and the original '52 drums on the rear. I am trying to use the master cyl. from a 2000 S-10. I do not have a proportioning valve installed.

1 out of 1 people think this is helpful.
65,905

I believe you'll need a proportioning valve on the system to regulate the pressures front to back. To my knowledge all disc/drum systems have always used them. HTH. -Jim

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