Can't get air out of brake line? - Team Camaro Tech
Brakes, Suspension & Steering Conversion questions, Steering & Handling

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post #1 of 16 (permalink) Old Sep 24th, 02, 03:57 AM Thread Starter
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I have a 69 power disc/drum car with proportioning block and metering valve. Everything on the brake system except for the above items is new.The rear brakes bleeded
fine .Started to do
the front and can't get the air out. I have even held the button in on the metering valve
while some body pumped the brakes, I then went and cracked the bleeders still lots of air . I have looked for leaks and I don't see any. Any ideas?
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post #2 of 16 (permalink) Old Sep 24th, 02, 05:38 AM
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May need to bench bleed the master cylinder again.

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post #3 of 16 (permalink) Old Sep 24th, 02, 06:04 AM
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I will assume that the PB system that you have is stock. Meaning that the PRO VALVE is GM issue. I had the same problem. You will have to get a small C-clamp and clamp down the little "nub" on the back side of the PRO valve. This will release the ball bearing inside the PRO valve thus, letting you bleed the air out. I was confused at the time also since the "nub" on the back of the PRO valve looks to be casted into the piece and not a moveable part. But, it works. Let me know if you want pics. Hope this helps.

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post #4 of 16 (permalink) Old Sep 24th, 02, 06:34 AM Thread Starter
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I think Im going to try clamping the rubber boot on the metering valve while having someone pump the brakes. The only problem is there is only about 1 inch between the button and booster not alot of room for a clamp.But I'll try rigging something just thought there might be a quick fix. And if that doesn't work I'll bleed the master again.
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post #5 of 16 (permalink) Old Sep 24th, 02, 07:28 AM
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I put an aftermarket master cylinder on my bro's 79 Z and it was bad. Could bleed the air. Took it back and exchanged it, it worked fine.

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post #6 of 16 (permalink) Old Sep 24th, 02, 08:47 AM
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It is possible you have a bad metering valve. This happened to me, but not as bad as yours sounds. On mine, I was ablre to get the brakes bled fine. However a couple of days later, I would go out and the pedal would be mushy. Turns out that the metering valve was leaking out the back. You might check the frame underneath the valve and see if there is any fluid.

Also, I do not believe you have to mash the button on the back when manually bleeding the brakes. You only have to do it if you are using a power bleeder like the dealerships do. A power bleeder pushes fluid from the MC into the lines using compressed air. If you had to push the button while manually bleeding the brakes, then the brakes wouldn't work when you mashed the pedal trying to stop because fluid couldn't get past the valve.

P.S. I got sick of trying to make the old parts work and wound up buying the combo valve conversion sold by Rick's. It has worked great. However, if you are doing a correct resto, it's probably not what you would want.



[This message has been edited by gheatly (edited 09-24-2002).]
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post #7 of 16 (permalink) Old Sep 24th, 02, 09:24 AM
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That valve is a metering valve not a proportioning valve. The rubber boot can be pried off without damaging it. Look at the pin for leakage. There is an O ring seal that can be changed if you remove the valve and take it apart.

If you are bleeding with a clear plastic hose over the bleeder screw, bubbles can be drawn past the bleeder threads by siphon action, and may not be actually coming from the caliper. I use teflon tape on the bleeder screws to prevent this.

Check the brake hoses where they connect to the calipers. I've heard some complaints of replacement hoses with banjo fittings that are too narrow to seal correctly, the bolt bottoms.
The metering valve can be left out if you have a stick shift or don't drive on ice.

The metering valve only works when you are applying the brakes very very lightly. I posted a new explanation on it's function on my page.
David

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[This message has been edited by davidpozzi (edited 09-24-2002).]
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post #8 of 16 (permalink) Old Sep 24th, 02, 10:10 AM
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Ole Dick Guldstrand passed on a bit of advice that has worked for him, for quite a few years.

Let gravity do the work for you. Crack all the bleeders loose and let it drip....just check the level in the master about every 15 minutes. Then after say 30-45 minutes begin closing the bleeders starting with passenger rear -drivers rear, pass front -drivers front and test.

When my '67 had stock metering and proportioning this was the only way to get ALL the air out, and I didnt even have to pump a pedal.

Food for thought.....
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post #9 of 16 (permalink) Old Sep 24th, 02, 12:17 PM
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You don't have to mash the button down. I tried gravity bleeding the system while building my car and after one week the fluid never made it to the front caliper lines. You may think that it sounds crazy but, it works. Pick up on of those "How To Restore Your Camaro" books and it'll show you. In particular, the book with the butternut yellow '67 and the pea green '72 on the front cover. Don't worry about the space behind the valve. I actually used a 3" c-clamp and ground down the top of it with a bench grinder to insure that the tool would fit. I am sure that everyone that has answered this post knows what they are talking about but, the procedure that I outlined in my first post worked for me and I have good braking. Just my .02

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post #10 of 16 (permalink) Old Sep 24th, 02, 02:40 PM
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We have the same parts, just a different approach and procedure, and still have gotten the results we were looking for. Thats why I love this site, there are so many ways to accomplish something, yet no one has been able to try everything once. But sharing our ideas is what get us down the road.

[This message has been edited by chacane67 (edited 09-24-2002).]
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post #11 of 16 (permalink) Old Sep 24th, 02, 04:37 PM
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Make sure you have installed the calipers right, if you mix left to right the bleeders will end up on the bottom of the caliper and you will never get the air out!! I have seen that happen many times.Just a thought. Mr Cool
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post #12 of 16 (permalink) Old Sep 24th, 02, 06:21 PM
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Tom, I like your additude!
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post #13 of 16 (permalink) Old Sep 24th, 02, 09:03 PM
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Thanks David.....love your show.
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post #14 of 16 (permalink) Old Sep 25th, 02, 03:41 AM Thread Starter
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Thanks for all the suggestions.Im going to try the teflon tape on the bleeder screws first. I have inspected everything for leaks
including around the the metering valve and proportioning valve,not a drop. Also the button on the metering valve moves smoothly.
The next step will be to clamp the valve open if necessary.After reading the posts I have a feeling
that the bubbles I'm seeing in my clear hose are from the bleeder screw threads because the pedal is hard and doesn't go to the floor. Back to the garage.
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post #15 of 16 (permalink) Old Sep 25th, 02, 05:10 PM
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Let us know how it works out

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