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Old 10-17-2006, 05:04 AM
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No consistent brake pedal

If anyone can lend some tips on my problem I would greatly appreciate it.
I purchased a corvette style after market disc/disc m/c with pop valve for my 62 nova. I have bleed about 2 quarts for fluid through the system and seem to have all the air out. My problem is I have no consistent brake pedal. After it sits for a bit, I get about 1/3 pedal, which can be pumped up, and is better while I am using the brakes, but returns back to the low soft pedal. The brakes stop well even with the low pedal and with a couple of pumps even better. thanks, rick

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Old 10-17-2006, 05:20 AM
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Did you bench bleed the M/C? And do you have any residual pressure valves installed? And do you have four wheel disc brakes? I,m almost sure any new Corvette M/C would be for all wheel disc brakes.
Just some thoughts

Randall
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Old 10-17-2006, 07:42 PM
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Randal

Yes, I did bench bleed the M/C, and I have 4 wheel disc. I have not installed a residual valve. I thought maybe the pop valve or the M/C had some residual. I have never had any dealings with a residual valve. Where does a man get one and where does it install???
thanks,
rick
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Old 10-18-2006, 12:58 PM
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Please give us some more info.
What year, make, model are your front and rear brakes?
Where is your master cylinder mounted?
What valves do you have in the brake line?
Have the flex lines been replaced?

If you are using ~83 or GM newer calipers on either end they are made with different angles cut into the o-ring grove that retracts the piston more then older stuff. GM used step-bore master cylinders to compensate for this.
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Old 10-18-2006, 02:55 PM
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You've got air in the system still. It's aggravating to here, but it's true. You cannot compress brake fluid, but you sure can compress air.

Residual valves are used in applications in which the master cylinder is positioned in the floor and backflow from the lines, and calipers can take place.

If your master cylinder is on the fire wall, and your lines are all below the master cylinder, you really don't have to have residual valves, although you can still use them.


When I think of air trapped in a system, I think of a see-through fuel filter with an air bubble in it. You can pass 10 tanks of fuel through it and still have air trapped in it.

You have not bled the air out of the system.


Brian
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Old 10-18-2006, 03:04 PM
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Along with air in the system there's a possibility your master cylinder could be losing pressure.

Check this article out: http://www.babcox.com/editorial/tr/tr502b.htm

Where they say:

"Vehicles with a leaky master cylinder are unsafe to drive because there's no telling when the pedal might go all the way to the floor with little or no application of the brakes. Low or soft pedal can also occur if there is air in the brake system, but the pedal won't continue to sink once the air has been compressed by steady pressure or repeated pumping."
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Old 10-18-2006, 03:31 PM
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My calipers or 90's trans am on the rear, the fronts came with my tci front subframe kit. I assume mustang 2 style. M/C is on the firewall, all the flex lines are new. No valves in the lines.


If I have air trapped, other than just bleeding, how can I get it out?


The M/C holds solid once pumped up, so I dont think it is leaking.
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Old 10-18-2006, 03:34 PM
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You will need to power bleed it to get all the air out. Either pressure or vacuum (what I use) should work.

Do the rear brakes have the e-brake as part of the caliper? If so that could very well be your problem. It is a very poor design that no one uses any more. It uses the e-brake to adjust.
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Old 10-18-2006, 05:10 PM
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the rear calipers do have the e-brake, but I am not using them.
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Old 10-18-2006, 06:56 PM
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Those caddy calipers, on many applications, position the high spot of the caliper piston above the bleeder screw.

May have to remove caliper from the bracket, and tilt it back to bleed. And E-brake adjustment is necessary. These calipers rely on E-Brake usage to keep them adjusted. The E-brake arm actually pulls the piston away from the pads, if not adjusted correctly.

Bryan>>>>>>>>>has had the same issues
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Old 10-18-2006, 07:26 PM
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Thanks Bryan
I will have to check the bleeder screws relation to the top of the piston. Do you know of some other caliper I can use to replace what I have now.
rick
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Old 10-18-2006, 07:38 PM
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I am noticing that you are in Texas
If you are planning to register this car for the street--Classic Car or standard plates--you need that E-Brake, and it has to hold the car at idle, in Drive.

If you are certain that you wish to change the calipers, Classicperform.com
will be able to give you information, Most of the people there are very helpful.

Classic Performance Products

One of the techs there was very helpful to me. Took me quite awhile before I got my 4-whl discs working right. Taking even longer to remember to use the parking brake

Bryan
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Old 10-18-2006, 07:45 PM
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I am in a small town, state inspections are quite lax here. I just had it inspected for the first time since I started the project. That is with windshield wipers removed, no e-brake, forgot the insurance card, and my had forgot to reinstall my vin tag. I do have all the light working, but he didn't check them either!!! Sometimes life in a small town is great.
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Old 10-20-2006, 08:33 PM
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. These calipers rely on E-Brake usage to keep them adjusted. The E-brake arm actually pulls the piston away from the pads, if not adjusted correctly.

even if you did ease through inspection you need to stop safe, after all that might be ME in front of you at the next light. Good Luck.
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Old 10-21-2006, 06:23 AM
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Well, I finally got them working properly. Great solid pedal, with good even braking. I adjusted the rear calipers manually and re-bled the system including bench bleeding the M/C. I guess I will have to dig out the park brake hardware and get it hooked up.
THANKS TO EVERYONE WHO POSTED INFORMATION TO HELP ME THROUGH THIS PROBLEM. Hope I can be of some help to you some day.
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