Proportioning Valve - Team Camaro Tech
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post #1 of 11 (permalink) Old May 1st, 17, 11:36 AM Thread Starter
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Bill
 
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Proportioning Valve

I just installed a new master cylinder and booster in my 69 Camaro (front disc/rear drum). I bench bled the MC installed everything, I made sure I had a little play in the brake pedal when I connected the rod to the booster. Front brakes bled easily with the speed bleeders, rear brakes I get nothing when I try to bleed them. Could this be a proportioning valve issue?

When I test drove it, I can press the brake pedal with it in drive and give it gas until the wheels spin; when I get it up to 40-50 mph, the car stops, but it takes a little longer than it should and the wheels will not lock up.

Any ideas out there? Thanks!

Bill
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post #2 of 11 (permalink) Old May 1st, 17, 12:27 PM
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Re: Proportioning Valve

If you didn't get any fluid out when you were bleeding your rear brakes I would keep bleeding. Sometimes the rears can take a really long time.

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post #3 of 11 (permalink) Old May 1st, 17, 01:18 PM Thread Starter
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Re: Proportioning Valve

Thanks! I guess it's back to the garage. They dont feel spongy though.
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post #4 of 11 (permalink) Old May 1st, 17, 02:17 PM
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Re: Proportioning Valve

No fluid.....no brakes. Working on fronts only.

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post #5 of 11 (permalink) Old May 1st, 17, 04:14 PM
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Re: Proportioning Valve

Very possible the rear flex line has collapsed internally.
If you haven't changed it already then do so. They can
look fine on the outside and be shot on the inside.
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post #6 of 11 (permalink) Old May 1st, 17, 04:24 PM Thread Starter
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Bill
 
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Re: Proportioning Valve

That's what they feel like, I can't figure out why there is no fluid going to the rear drums. when I replaced the bleeders there was a little that came out, but not much.
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post #7 of 11 (permalink) Old May 1st, 17, 04:54 PM
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Re: Proportioning Valve

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Originally Posted by Baso View Post
Thanks! I guess it's back to the garage. They dont feel spongy though.
Bill, as aforementioned, no juice, no brakes. If you cannot get brake fluid to rear drums start to find out why by back tracking to see where the fluid is not coming from but as we all know brake fluid can make a mess with paint so hopefully your using synthetic. I had a very similar issue like yours before and it was the master cylinder that had been rebuilt with a wrong piston (too long).

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post #8 of 11 (permalink) Old May 1st, 17, 05:51 PM Thread Starter
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Bill
 
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Re: Proportioning Valve

Thanks, I will do that. The MC and booster are from SS Brakes, brand new out of the box; I did have an issue in that they sent the wrong plug for the piston in the MC, but they corrected that and everything fits now. So I will try working my way back from the flex line to the valve under the MC, hopefully it will be an easy find. BTW I'm using (Car Quest) Dot 3 fluid; it is what is stamped on the MC cover.

I appreciate everyone's input. Once I find it, I'll close up the thread so anyone else that runs into this can see it.
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post #9 of 11 (permalink) Old May 2nd, 17, 05:01 AM
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Re: Proportioning Valve

Have you tried vacuum bleeding? I've had really good luck bleeding lines that way.

Make sure the prop valve is allowing maximum rear braking and vacuum away until you get a clear stream of brake fluid on both sides. Start with right rear, then left rear.


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post #10 of 11 (permalink) Old May 2nd, 17, 09:29 AM
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Re: Proportioning Valve

x2 for the vac bleeding. I had a similar issue on my 68 and bought a vac bleeder. With that it only took about 35 minutes to get everything bled to where I felt comfortable.
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post #11 of 11 (permalink) Old May 2nd, 17, 11:20 PM
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Re: Proportioning Valve

Quote:
Originally Posted by Baso View Post
I just installed a new master cylinder and booster in my 69 Camaro (front disc/rear drum). I bench bled the MC installed everything, I made sure I had a little play in the brake pedal when I connected the rod to the booster. Front brakes bled easily with the speed bleeders, rear brakes I get nothing when I try to bleed them. Could this be a proportioning valve issue?

When I test drove it, I can press the brake pedal with it in drive and give it gas until the wheels spin; when I get it up to 40-50 mph, the car stops, but it takes a little longer than it should and the wheels will not lock up.

Any ideas out there? Thanks!

Bill
The usual problem is you need .010" play between the booster pushrod that goes into the master cyl. Often it's too long and won't allow the MC rear piston to return fully and uncover the replenishment port to refill it.

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