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cfgj1969, Auto Mechanic
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Chevrolet Silverado 1500: Bleeding brake system on a 1997 Chevy

Customer Question

Bleeding brake system on a 1997 Chevy silverado.
2 person system.
there are many suggestions on how to EXACTLY do this, please explain step by step.
Do you have key in On or Off position?
Do you press pedal down SLOWLY, then wait a few seconds before depressing it again, or do you pump it constantly until you get pressure?
WHERE EXACTLY is the proportioning valve plunger that is supposed to be c-clamped in the "in" position when bleeding?
Submitted: 2 years ago.
Category: Chevy
Expert:  dghardysr replied 2 years ago.
Hello, and thanks for using Just Answer. My name is David and I will be helping you. Here are the directions for bleeding the system. Hope this helps. If I have answered your question to your satisfaction, pleas accept so that I will receive credit for it. Thanks and have a great day.

BLEEDING BRAKE SYSTEM

NOTE:On Hydro-Boost, check for air bubbles in power steering fluid reservoir. If air bubbles are present, bleed Hydro-Boost system before bleeding brake system.

MASTER CYLINDER BLEEDING

NOTE:To prevent air from entering brake system, bench bleed master cylinder before installing.
  1. Place master cylinder in soft-jawed vise with front end tilted slightly down. DO NOT overtighten vise. Plug both outlet ports of master cylinder. Fill master cylinder reservoir.
  2. Press and release piston about 1" (25 mm) several times. As air is bled from master cylinder, the primary piston will not travel the full 1" (25 mm) stroke.
  3. Repeat previous step with front end of master cylinder tilted slightly up. Reposition master cylinder in vise to level position. Loosen front outlet plug and push piston into bore to expel air from cylinder. Tighten plug and allow piston to return to original position. Repeat procedure at rear outlet plug.
  4. Fill reservoir and install master cylinder. DO NOT fully tighten brake lines at this time. Slowly press brake pedal to floor and hold. Tighten brake lines. Release brake pedal. Bleed brake system.

MANUAL BLEEDING

NOTE:Air tends to cling to caliper walls. When bleeding vehicles with disc brakes, lightly tap caliper to help remove air.
  1. Deplete vacuum reserve from power brake booster by depressing brake pedal several times with engine off. Fill master cylinder and keep at least half full during bleeding procedure. If master cylinder is not known or suspected to have air in bore, go to step 4). If master cylinder is known or suspected to have air in bore, go to next step.
  2. Disconnect forward brakeline fitting at master cylinder. Allow fluid to flow from fitting. Tighten fitting to specification. Have an assistant depress brake pedal slowly and hold. Loosen forward fitting. Tighten fitting while pedal is still at floor. Release brake pedal slowly. Wait 15 seconds.
    NOTE:Rapid pumping of brake pedal causes master cylinder secondary piston to move into a position that makes bleeding system difficult.
  3. Repeat step 2), including 15 second wait, until fluid is clear and free of air bubbles. Repeat procedure at other (rearmost) brakeline fitting on master cylinder. Master cylinder is now bled. If wheel cylinders/calipers are not suspected to have air in them, it is not necessary to bleed them.
    NOTE:On vehicles with 4WAL, if Brake Pressure Modulator Valve was replaced, or is suspected to have air trapped inside, it must be bled next.
  4. If wheel cylinders/calipers are known or suspected to have air in them, raise and support vehicle. Remove bleeder valve cap from right rear wheel. Place proper size box end wrench over bleeder valve. Attach one end of clear tube over valve and submerge other end in container partially filled with clean brake fluid.
  5. Have an assistant depress brake pedal slowly and hold. Loosen bleeder valve to purge air from cylinder. Tighten bleeder valve and slowly release brake pedal. Wait 15 seconds. Repeat sequence, including 15 second wait, until all air is removed.
  6. Remove tube and wrench. Repeat step 5) at left rear, right front, and left front wheels in this order. Fill master cylinder reservoir, and install cover. Ensure there is no sponginess in brake pedal and that BRAKE warning light is off.

PRESSURE BLEEDING

NOTE:Air tends to cling to caliper walls. When bleeding vehicles with disc brakes, lightly tap caliper to help remove air.
WARNING:DO NOT use rigid clamp to position hold-off valve stem. This may damage valve assembly, causing brake failure.
  1. Retain hold-off valve stem of combination valve using Valve Retainer (J-23709) on Commercial Van, or (J-39177) on all other models. See picture below. This allows brake fluid to flow through combination valve and entire system during bleeding.
  2. Clean master cylinder cap and surrounding area. Remove cap. With pressure tank at least 2/3 full, connect pressure bleeder to master cylinder with adapters. Attach bleeder hose to right rear bleeder valve.
    NOTE:On vehicles with 4WAL, if Brake Pressure Modulator Valve was replaced, or is suspected to have air trapped inside, it must be bled next.
  3. Place other end of hose in glass jar partially filled with brake fluid so end of hose is submerged in fluid. Open release valve on pressure bleeder. Set pressure bleeder to 20-25 psi (1.4-1.8 kg/cm2 ) or pressure specified by equipment manufacturer.
  4. Open bleeder screw 3/4 - 1 turn and note fluid flow. Close bleeder screw when no air bubbles are present in fluid flow. Repeat procedure on left rear, right front, and left front wheels in this order.
  5. Check brake pedal operation. Remove pressure bleeder. Remove valve retainer from hold-off valve. Refill master cylinder reservoir, if necessary.

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Customer: replied 2 years ago.
We will try and get back to you
Expert:  dghardysr replied 2 years ago.
ok, hope you won't have any troubles with it.
Customer: replied 2 years ago.
Do you keep plunger depressed on MC?
Customer: replied 2 years ago.
Relist: Incomplete answer.
Isn't working still spongy brakes have more questions
Customer: replied 2 years ago.
Didn't take sponginess out of brake system
Have changed Master Cylinder and booster
Got plenty of vacuum.
Calipers, wheel cylinders, all rubber hoses, shoes, pads and drums.
What else could be the issue?
Customer: replied 2 years ago.
Is anyone there???
Expert:  cfgj1969 replied 2 years ago.
If you are sure that rear shoes are adjusted properly and front pads are new, but pedal is still spongy, there's still air in your system somewhere. I've had this problem before on trucks. I would recommend that you try what is known as "gravity bleeding". To do this, first make sure master cylinder is full. Leaving cap off master cylinder, connect a hose to any of your four bleeder screws. I usually start at right rear because it is farther from master cylinder. Crack bleeder valve and put hose into container large enough to hold full container of brake fluid. Let it bleed until you have ran an entire container of fluid thru it. Then, repeat it on the other three wheels. Make sure during this process that the master cylinder is never below half full.

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