89 Chevy 2500 Brakes

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  #1  
Old 08-12-04, 12:38 PM
Huntertb1
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89 Chevy 2500 Brakes

I have an 89 chevy 2500 2wd P/U, 305 V-8, with 700R4 and changed the brakes pads on it recently.

when I finished I jumped in, and started it up, and applied the breaks, and to the floor they went as expected, when I pumped them again, same thing, in fact, here it is a week later, and still to the floor.

what did I do wrong?

I compressed the caliper pistons with a c-clamp, like I always do with no problems, and changed the pads, simple as that.

someone told me that I may have blown out a seal in my master cylinder so I will be getting a new one of those soon, I finally bled the brakes today and do have some pedal back but nothing like it was.

I have an extra component under my master cylinder that I am not familiar with, there is a power booster, master cylinder, and proportioning valve, but there is also a cylinder under my master cylinder with a bleeder valve on it, and there is also a fairly large slim rectangle black box with 2 wire connecters on it, and I noticed that when my brake light comes on (as it has for 3 years occasionally) if I umhook the 2 clips from that black box and replug them back in, the light will go out for a few days or longer, depending on driving conditions.


I guess what I need to know is, what is the black box for, and what is the extra cylinder, and can someone give me step by step instructions or a link on how to bleed the ENTIRE brake system?
 
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  #2  
Old 08-12-04, 02:30 PM
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If you didn't open a bleeder screw it isn't air in the system it's most likely dirt in the isolation/dump valve caused by pushing the pistons back without opening the caliper bleeder screws.The black box by the master cylinder is the abs module the cylinder is the valve I mentioned.I have never been able to bleed the dirt out of the valve.You can try just bleed the valve several times then bleed all 4 wheels.
 
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Old 08-12-04, 06:11 PM
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Black box

The black box is the ABS computer.
 
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Old 08-13-04, 08:50 AM
Huntertb1
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Thanks for the info.

So if I can't bleed this thing out, it is more likely that I need a new isolation dump valve, and probably not a master cylinder?

I didn't think I had ABS.

I don't think it is working then
 

Last edited by Huntertb1; 08-13-04 at 09:06 AM.
  #5  
Old 08-13-04, 09:01 AM
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rear wheels

You only have rear wheel ABS I know I had a 89 Chevy c-2500 but with a 350 and a turbo 400 trans.
 
  #6  
Old 08-13-04, 02:05 PM
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Yes you need a new valve and if the light keeps coming on you also need the abs module if you want the abs to actually work.Be warned the valve and module are not cheap.Used parts would be a mighty big gamble also so don't even go there.Before you go much further buy a small piece of brake line and some type of fitting to seal one end.Install this in the master cylinder port that goes to the dump valve bleed it as best as you can(don't run the master low).After this has been bled see if you now have a good/better brake pedal.If you do the valve is bad.If you still have a bad pedal you may have a master cylinder problem.This test removes the valve from the equation for you before you open your wallet.You also have a pm.
 
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Old 08-15-04, 04:39 AM
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I've never seen an isolation/dump valve for the rear wheel antilock brakes cause a pedal feel issue. Are you sure you didn't blow out a brake line somewhere when you where jumping on the pedal? The line to the rear axles on those had a bad habit of rusting out near the fuel tank, especially if you live in an area that salt is used on the roads. I had to replace it on my `92.
 
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Old 08-15-04, 07:02 AM
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Originally Posted by bigguy05641
I've never seen an isolation/dump valve for the rear wheel antilock brakes cause a pedal feel issue.
If you work as often as you post here then we know why.Just because you have not seen it doesn't mean it doesn't happen.Hunter bled the brakes I would think leaking brake lines would be obvious while under the truck and having brake fluid sprayed in your face.I could be wrong though.
 
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Old 08-15-04, 08:15 AM
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Originally Posted by bigguy05641
I've never seen an isolation/dump valve for the rear wheel antilock brakes cause a pedal feel issue.
Of course a dump valve can cause a pedal issue. That's what it does.....dump brake fluid. That causes pedal loss. If he had a leaking, it would be pretty obvious that he was losing brake fluid, even if he didn't see it coming out.
 
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Old 08-18-04, 05:52 PM
Huntertb1
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Originally Posted by bigguy05641
I've never seen an isolation/dump valve for the rear wheel antilock brakes cause a pedal feel issue. Are you sure you didn't blow out a brake line somewhere when you where jumping on the pedal? The line to the rear axles on those had a bad habit of rusting out near the fuel tank, especially if you live in an area that salt is used on the roads. I had to replace it on my `92.


Believe me, I checked everywhere for leaks, I followed all of the lines to each wheel, checked the high pressure rubber sections to the front wheels, and checked the calipers, and wheel cylinders, not a drop anywhere of fluid.
 
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