Tech Tips

SPONGY OR LOW PEDAL

  • Air in rear calipers. FixGravity bleed rear calipers.

  • Air in front calipers. Fix: Bleed entire system.

  • Rear calipers with parking brake out of adjustment.  FixAdjust parking brakes.

  • Pulling piston back too much. Fix: Adjust caliper brake arms.

  • Defective caliper.   Fix: Replace caliper.

BRAKES GETTING HOT (REAR ONLY)

  • Residual pressure valve in master cylinder or combination valve causing calipers to drag.  Fix: Adjust clearance on pedal push rod so master cylinder returns against its stop.

  • Drum system with residual pressure valves for front and rear.  FixRemove residual valve.

BRAKES GETTING HOT (FRONT AND REAR)

  • Master cylinder return hole blocked causing calipers to not retract.  Fix: Adjust clearance on pedal push rod so master cylinder returns against its stop.

  • Drum system with residual pressure valves for front and rear.  FixRemove residual valve for front and rear.

CALIPER MOUNTING SCREWS SCRAPE ON TOP OF ROTOR

  • Master cylinder return hole blocked causing calipers to not retract. Fix: Check bracket it should be parallel with the rotor. Grind sleeves or bend bracket (as low as possible) until the bracket is parallel. Hold bracket up on it's mounting holes and then tighten bolts.

BRAKE LIGHT ON DASH COMES ON

  • Air or leak in either the front or rear brake system.  Fix: Bleed the system.

CAR PULLS TO ONE SIDE OR ONE WHEEL LOCKS UP

  • Brake fluid or grease on pads.  Fix: Clean pads or replace.

PEDAL LOWER THAN YOU LIKE

  • Movement to apply calipers makes pedal too low.  Fix: Add two pound residuals to either the front, rear or both systems.

INSIDE PADS WEARING BUT NOT OUTSIDE PADS

  • Residual valve allowing caliper to open up some but not enough.  FixEliminate residual valve.

CALIPER PARKING BRAKES DON'T HOLD

  • Parking brake mechanism out of adjustment.  FixAdjust calipers.

REAR BRAKES LOCK UP BEFORE THE FRONT

  • Not enough proportioning to the front brakes and off of the rear brakes.  Fix: Add an adjustable proportioning valve to the rear line to reduce the rear brakes more.

NOT ENOUGH BRAKES

  • Larger and heavier wheels make brakes less effective  Fix: Change to larger rotors in front. bullet Install larger booster. Install master cylinder with smaller bore.

REMOVE RESIDUAL VALVE

The residual valve holds ten pounds on a drum brake system when the brakes release to keep the spring on the shoes from collapsing the wheel cylinders. Residual valves can be found in the end of the cylinder in ford fruit jar single master cylinders, where the brake lines screw into the master cylinder on some dual cylinders, one in the rear line only on front disc rear drum systems, or in the combination valve rear line only. You can remove the residual valve from the master cylinder where the brake line screws in with a sheet metal screw. Screw it in and then pull. It will come right out.

GRAVITY BLEEDING

Calipers, especially rear calipers with all the parts and crevices can trap air inside them. Gravity bleeding is the best method we have found to bleed calipers. To gravity bleed, take the caliper off the bracket but leave the flex hose connected. Take the top off the master cylinder and keep filled. Hold the caliper so the flex hose is going slightly uphill to the caliper. Open the bleed screw so fluid and air will slowly come out of the bleeder. You can move the caliper around, hit it with a rubber hammer to knock air bubbles loose. When the fluid runs clear, do the other side and then do both calipers again. (Do not push the pedal until you install the calipers on the rotors) Remember that air bubbles rise. The bleed screw must be at the top where it breaks into the caliper cylinder to get the air out. (The bleeder might be pointing to the front) Rear calipers have their mounting screws one above the other. Front calipers sit on approximately a 45-degree angle.

Adjust Caliper Parking Brakes The GM rear caliper with integral parking brake is self-adjusting when you use the parking brake. As the pads wear it will click to the next stop, but they do not always work and they will not work if you do not use your parking brake.

TIPS FOR A SUCCESSFUL INSTALLATION

  1. Pinch off the rubber line between the frame and axle. This will keep the fluid in the lines and make it easier when you bleed the system.

  2. Grind off any projections on the caliper that might hit the bracket.

  3. Remove the spring from your parking brake cable, it will coil bind with the rear calipers.

REAR CALIPER PARKING BRAKE LEVER ADJUSTMENT

Note: This procedure must be performed as part of the rear caliper replacement operation. Failure to adjust the parking brake lever before you apply the hydraulic brakes, can result in no parking brake and possible premature brake wear or damage. Adjust the parking brake levers by disconnecting the cables, taking the springs off,  and then pushing the lever all the way forward and backward rapidly. Each time you push them they should move off of the stop less. To be properly adjusted, they should only move off of the stop 3/8 to 1/2 inch. If they will not adjust try putting a lever between the rotor and the pad and putting pressure on the piston. Now push the lever releasing pressure on the pad as the caliper adjusts. These are the only two ways we know of to adjust the parking brake. If the calipers won't adjust you will have a low pedal and the piston will retract too far and will use up all your hydraulic pedal travel to put the brakes on. Once the parking brake calipers ore adjusted put a c-clamp on between the lever and the bracket to hold the brakes locked up. Note: An easy test for proper lever position is to grasp the brake pad and try to shake it. If any rattling is heard, the parking brake lever requires adjustment.

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