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I'm in the process of troubleshooting the brakes on my TH83…

Hi, I'm in the process...
Hi, I'm in the process of troubleshooting the brakes on my TH83 S/N:3RN00543 which I believe makes it a 1998 model. I've gone through all the maintenance for the axles, now I want to try purge the brake system. Is there a procedure for purging the brake system of air without specialty tools or hoses?
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Answered in 1 hour by:
1/9/2020
Mechanic: Dan, Technician replied 2 years ago
Dan
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Mechanic: Dan, Technician replied 2 years ago
  1. Start the engine.

     

    1. Park the machine on level ground and lower the boom. Engage the parking brake.

     

    1. Place wheel blocks in front of the wheels and behind the wheels.

     

    1. Disengage the parking brake and stop the engine.

    Illustration 1g00663930

    Location of the Purge Screw on the Axle Housing

    1. Remove the dust caps from the purge screws. Remove the purge screws from the front axle housing and the rear axle housing. Fill the brake chambers through each hole with clean oil.

      Refer to Operation and Maintenance Manual, SEBU6865, "Lubricant Specifications" and Operation and Maintenance Manual, SEBU7112, "Lubricant Specifications".

     

    1. Install the purge screws and tighten the purge screws.

    Illustration 2g00663956

    1. Remove the cap from the brake reservoir and fill the brake reservoir with clean oil.

     

    1. Start the engine and operate the engine at low idle.

     

    1. Loosen the nut on the left side rear hydraulic brake line. The hydraulic brake line is adjacent to the purge screw. Seek the assistance of a capable operator to push downward on the brake pedal. The full stroke of the brake pedal must be used and the brake reservoir must be topped up during the purging if it is necessary. When the brake pedal is at full stroke, hold the brake pedal down and tighten the brake line nut. Slowly release the brake pedal until the brake pedal is fully released. The brake pedal must be fully depressed and the brake pedal must be fully released in this way until the oil runs from the brake line nut free from air bubbles. When the oil is free from air bubbles the brake pedal must be held down while the nut is tightened. Repeat this procedure at the right side rear hydraulic brake line.

     

    1. The procedure should also be repeated at the right side front hydraulic brake line and at the left side front hydraulic brake line.

     

    1. Install a piece of tubing (clear plastic) over the left side rear purge screw and place the free end of the tubing into a suitable container.

     

    1. Loosen the left side rear purge screw and push the brake pedal fully downward. Hold the brake pedal fully downward and tighten the purge screw. Release the brake pedal slowly. Repeat the procedure until the oil flows free of air.

     

    1. Repeat the procedure at the right side rear purge screw.

     

    1. Repeat the procedure at the left side front purge screw and at the right side front purge screw.

     

    1. Stop the engine and allow the machine to stand for 5 minutes in order to allow any air bubbles in the oil to rise to the surface.

     

    1. Repeat Steps 11 to 14 if it is necessary. Stop the engine.

     

    1. Fill the brake reservoir to the correct level and install the cap. Install dust caps on the purge screws.

     

    1. Engage the parking brake. Remove the wheel blocks from the front of the wheels and the rear of the wheels.

    Second Type of Brake System

    Table 1

    Tool List for Purging Air from the Brake System

    Qty Part Number Description

    1 (###) ###-####(1) Cap

    1 (###) ###-####(2) Cap

    2 2D-7325 Pipe Tee

    3 1P-9328 Fitting

    3 1P-4278 Hose Clamp

    1 6V-4144 Coupler

    1 5P-8998 Fitting

    1 1S-8937 Needle Valve

    1 6V-3966 Fitting

    12 m (39 ft) 148-7109 Tubing (Clear Plastic)

    1 6V-7830 Pressure Gauge

    1 5P-3321 Adhesive

    ( 1 )Type one brake reservoir for the second type of brake system. The cap is supplied with the 090-8957 Reservoir .

    ( 2 )Type two brake reservoir for the second type of brake system.

    The Tooling in the tool list is needed in order to purge the air from the brake system.

    The following steps explain the procedure to follow in order to purge the air from the brake system.

    1. Start the engine.

     

    1. Park the machine on level ground and lower the boom. Engage the parking brake.

     

    1. Place wheel blocks in front of the wheels and behind the wheels.

     

    1. Disengage the parking brake and stop the engine.

    Illustration 3g00664302

    Installation of the brake purge Tooling.

    (1) Tubing (clear plastic)

    (2) Tubing (clear plastic)

    (3) Hose clamp

    (4) Fitting

    (5) Hose clamp

    (6) Fitting

    (7) Pipe tee

    (8) Hose clamp

    (9) Pressure gauge

    (10) Fitting

    (11) Fitting

    (12) Pipe tee

    (13) Needle valve

    (14) Nipple

    (15) Fitting

    (16) Pilot pressure port

    (17) Brake reservoir

    (18) Tubing (clear plastic)

    (19) Hydraulic tank

    (20) Purge screws

    (A) Type one brake reservoir.

    (B) Type two brake reservoir.

    Note: There are two types of brake reservoirs (17). If necessary, brake reservoir (A) and brake reservoir (B) can be identified by the cap that is installed on the brake reservoir on your machine. Refer to Illustration 3. Although brake reservoir (A) is included in the tool list, the brake reservoir is not used in the test procedure. Brake reservoir (B) is not included in the tool list.

    1. Match one of the two caps that are included in the tool list to the cap that is installed on the brake reservoir on your machine. Drill a 11 mm (0.435 inch) hole in the center of the new cap. Tap the drilled hole in the new cap with a 0.25 inch NPTF thread. Apply 5P-3321 Adhesive to the threads on the male end of 2D-7325 Pipe Tee (7). Install the male end of the pipe tee into the modified cap. Additional 5P-3321 Adhesive may be applied to the exterior surface of the modified cap around the male end of the pipe tee. Block the vent hole with adhesive.

      Note: The 5P-3321 Adhesive that has been applied should be completely hardened before the equipment is used in the test procedure.

     

    1. Remove the cap of brake reservoir (17) and top up the oil in the brake reservoir. Install the cap that was modified in Step 5 to the brake reservoir on the machine. Turn the cap until the seal is firmly in contact with the brake reservoir. Remove the filler cap for hydraulic tank (19). Place one end of tubing (18) into the filler tube for the hydraulic tank. Screw fitting (6) into pipe tee (7). Attach the other end of tubing (18) to fitting (6) .

     

    1. Secure tubing (18) with hose clamp (5) .

     

    1. Check that needle valve (13) is closed.

     

    1. Assemble the following components. Refer to Illustration 3 for the correct procedure.

       

      • (10) Fitting

         

      • (11) Fitting

         

      • (12) Pipe tee

         

      • (13) Needle valve

         

      • (14) Nipple

         

      • (15) Coupler

         

    Illustration 4g00684022

    Location of Pilot Pressure Port on the Control Valve

    1. Open the engine enclosure. Connect the assembled components to pilot pressure port (16) on the control valve.

      Note: The pilot pressure port can be identified by the hose that is marked "PS2" at the connection to the control valve.

     

    1. Install a length of tubing (2) to the horizontal fitting (4) on pipe tee (7) and secure tubing (2) with hose clamp (3) .

     

    1. Attach the other end of tubing (2) to fitting (10) and secure tubing (2) with hose clamp (8) .

     

    1. Attach pressure gauge (9) to fitting (11) .

     

    1. Start the engine and allow the machine to idle.

     

    1. Open needle valve (13). Adjust the needle valve until a pressure of 138 ± 35 kPa (20 ± 5 psi) is obtained. The hydraulic oil from the pilot system will now transfer pressure into the brake packs through the following components: brake reservoir, brake cylinder (master) and brake cylinder (boost).

      Note: The hydraulic pressure must not be allowed to exceed 345 kPa (50 psi).

     

    1. The brake system should be purged in the following order.

       

      1. Purge screw on the brake cylinder (boost)

       

      1. Purge screw on the right side of the rear axle

       

      1. Purge screw on the left side of the rear axle

       

      1. Purge screw on the right side of the front axle

       

      1. Purge screw on the left side of the front axle

    Illustration 5g00727549

    Brake cylinder (boost) is located inside the subframe in an area that is close to the rear of the cab.

    1. Remove the dust cover from purge screw (20) on the brake cylinder (boost). Install a length of tubing to purge screw (20). Place the other end of the tubing in the filler tube for the hydraulic tank.

     

    1. Loosen purge screw (20) on the brake cylinder (boost). Watch the oil that is returning to the filler tube for the hydraulic tank. The other tubing that is in the filler tube may be pinched by hand in order to increase the flow of oil through the brake system. Watch the pressure gauge as you pinch the tubing. Do not allow the oil pressure to go above 345 kPa (50 psi). Close purge screw (20) when the oil is free from air. Remove the tubing.

     

    1. Remove the dust cover from purge screw (20) on the right side of the rear axle. Install a length of tubing (1) onto purge screw (20). Place the other end of the tubing in the filler tube for the hydraulic tank.

     

    1. Loosen purge screw (20) on the right side of the rear axle. Watch the oil that is returning to the filler tube for the hydraulic tank. The other tubing that is in the filler tube may be pinched by hand in order to increase the flow of oil through the brake system. Watch the pressure gauge as you pinch the tubing. Do not allow the oil pressure to go above 450 kPa (65 psi). Close purge screw (20) when the oil is free from air. Remove the tubing.

     

    1. Repeat Steps 19 and 20 for the purge screw on the left side of the rear axle. Repeat Steps 19 and 20 for the purge screws on the front axle.

     

    1. Stop the engine and allow the machine to stand for 15 minutes in order to allow any air bubbles in the oil to rise to the surface. Repeat Steps 19 to 21 if you do not have sufficient brake pedal pressure.

     

    1. Remove the cap from the brake reservoir. Add hydraulic oil to the brake reservoir if it is necessary. Refer to Operation and Maintenance Manual, SEBU6865, "Lubricant Specifications" and Operation and Maintenance Manual, SEBU7112, "Lubricant Specifications". Install the original cap on the brake reservoir. Remove the equipment that was used to purge the brake system. Install the dust covers on all the purge screws and install the dust cover on the pilot pressure port. Close the engine enclosure.

     

    1. Engage the parking brake. Remove the wheel blocks from the front of the wheels and the rear of the wheels.
    Ask Your Own Construction and Road Equipment Question
    Mechanic: Dan, Technician replied 2 years ago

    This is the actual bleed procedure to properly bleed the brake system recommended by Caterpillar. Any other variations performed outside of this procedure may not properly bleed and get all of the air out of your system.

    Dan
    Dan, Technician
    Category: Construction and Road Equipment
    Satisfied Customers: 15,095
    Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
    Verified
    Dan and 87 other Construction and Road Equipment Specialists are ready to help you
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    Customer reply replied 2 years ago
    thanks, that'll work.
    Mechanic: Dan, Technician replied 2 years ago

    You are very welcome.

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