Brake master cylinder?
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Brake master cylinder? - 6/7/2007 5:46:24 AM
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new2chevy
Posts: 5
Joined: 6/7/2007
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Ok, so I bought my '97 1500 from a local chevy dealer, I noticed the brakes were acting funny, so I had them replace the rotors, they did. I have a lot of brake pedal travel the first time I depress it, and sometimes it even trips the switch that makes the brake light on the dash come on. But if I let go of the pedal and then depress it again they're fine, lots of pressure with little travel. I took it back, and they said they bled the brakes and that that fixed it, but it didn't. Could this possibly be my master cylinder going out?
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'97 Chevy 1500 - 5.7L - V8
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RE: Brake master cylinder? - 6/7/2007 6:22:42 AM
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lost_in_alabama
Posts: 72
Joined: 7/17/2006
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Sounds like it is the brake master cylinder.
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RE: Brake master cylinder? - 6/7/2007 6:39:51 AM
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new2chevy
Posts: 5
Joined: 6/7/2007
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Yeah, that's what I origionally told them to fix, but noooo, they fixed it by bleeding the brakes, or not.
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RE: Brake master cylinder? - 7/19/2007 1:47:33 PM
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Burb
Posts: 15
Joined: 6/22/2006
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My '99 Suburban has recently started doing the same thing at 150,000 miles. I replaced the front brake pads a few months back with no issues. I'm going to order a new master cylinder and put it in myself, but I have a question...
Is there any different technique for bleeding the brakes on this vehicle with the big Kelsey Hayes ABS system mounted on the inner fender?
I've replaced master cylinders before and will bench bleed the master culinder and then work from the right rear up to the left front. Is there anything special about the ABS I should be afraid or aware of? Thanks!
Rob (In Germany)
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RE: Brake master cylinder? - 7/19/2007 3:37:57 PM
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ZX1100F1
Posts: 2429
Joined: 8/1/2006
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Proceedures for bleeding ABS brakes on 1999 Suburban:
Antilock Brake System Automated Bleed Procedure Important: • Use the two-person bleed procedure under the following conditions: - Installing a new Electro-Hydraulic Control Unit (EHCU) or new Brake Pressure Modulator Valve (BPMV). - Air is trapped in the valve body • Do not drive the vehicle until the brake pedal feels firm. • Do not reuse brake fluid that is used during bleeding. • Use the vacuum, the pressure and the gravity bleeding procedures only for base brake bleeding. Two Person Procedure Raise the vehicle in order to access the system bleed screws. Bleed the system at the right rear wheel first. Install a clear hose on the bleed screw. Immerse the opposite end of the hose into a container partially filled with clean DOT 3 brake fluid. Open the bleed screw 1/2 to one full turn. Slowly depress the brake pedal. While the pedal is depressed to its full extent, tighten the bleed screw. Release the brake pedal and wait 10-15 seconds for the master cylinder pistons to return to the home position. Repeat the previous steps for the remaining wheels. The brake fluid which is present at each bleed screw should be clean and free of air. This procedure may use more than a pint of fluid per wheel. Check the master cylinder fluid level every four to six strokes of the brake pedal in order to avoid running the system dry. Press the brake pedal firmly and run the Scan Tool Automated Bleed procedure (below 15,000 GVW) once, or run the Function Test (above 15,000 GVW) four times. Release the brake pedal between each test. Bleed all four wheels again using Steps 3-9. This will remove the remaining air from the brake system. Evaluate the feel of the brake pedal before attempting to drive the vehicle. Bleed the system as many times as necessary in order to obtain the appropriate feel of the pedal.
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RE: Brake master cylinder? - 8/1/2007 7:35:21 AM
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Burb
Posts: 15
Joined: 6/22/2006
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Thanks. That sounds like the normal bleeding procedure with the exception of "...run the Scan Tool Automated Bleed procedure (below 15,000 GVW) once, or run the Function Test (above 15,000 GVW) four times."
I just got the master cylinder and the bench bleeding instructions are different than I've seen before. It has the plastic plugs for bleeding, but without nipples for tubes to run back into the resevoir! They are just solid plastic. The instructions say to use the plugs provided, but say nothing about running tubes back into the resevoir to remove air in the master cylinder. Maybe I'm too "old school", but is there some wierd internal bypass in new master cylinders that allows them to be bench bled with the brake line ports completely blocked!? Please help!!
Thanks,
Rob
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