Brake Purging Procedure For 8I-3432 Brake Control Group Caterpillar

THIS TIB REPLACES THE JUNE 4, 1997 TELEHANDLER TIB, COMPONENT CODE 4258, "BRAKE PURGING PROCEDURE FOR 8I-3432 CONTROL GROUP". DESTROY THE JUNE 4, 1997 TIB. IT WILL NOT APPEAR IN THE QUARTERLY INDEX.

Problem:

A new 8I-3432 Brake Control Group is currently being installed for new production machines listed above. Service Manuals do not contain the correct purging procedure. Additional information will be available in Service Magazine articles.

Solution:

This article describes the following:

1. How to assemble equipment needed for purging the 8I-3432 Brake Control Group

2. Special tools needed during the purge process

3. The procedure to purge air from the 8I-3432 Brake Control Group

Follow the steps of this procedure carefully, there is a need to depress the brake pedal frequently during this procedure.Parts Needed For Purge Equipment

Refer to Illustration 1 for the location of the parts of the purge equipment.

Illustration 1. Bleed screw cap (10). Bleed screw (11). Tetragage port (A). Connect to pilot pressure test port at hydraulic control valve (B). Modified reservoir cap (C). Hydraulic fill port (D).

Assembly and Modification Of Purge Equipment For 8I-3432 Brake Control Group

1. Remove the cap from the 090-8957 Reservoir to be used for the purge equipment.

2. Using the cap from 090-8957 reservoir mentioned in step 1, drill and tap a .250"-18NPTF hole to accept the 2D-7325 Tee. Use 5P-3321 Fast Cure Epoxy Mixercup to fasten the 2D-7325 Tee to the cap. Use the cap only, the rest of the reservoir assembly is not used for the bleed procedure but provides a handy storage compartment for the clamps when not in use.

3. Plug the vent hole in the cap of the 090-8957 Reservoir which is used for purge equipment using 5P-3321 Fast Cure Epoxy Mixercup. All epoxy used for this procedure should be completely hardened before the assembly is employed in the test procedure.

4. Assemble the kit as shown in Illustration 1 without connecting the tubing. The tubing length for E and F is approximately 3.5 m (12 ft) each.

NOTE: If the brake system has been disassembled or the oil has been drained for any reason, the brake hydraulic system should be refilled and bled with the engine operating using the following procedure:

1. Park the machine on level ground.

2. Raise the boom and install the boom lock, if equipped. The procedure is in the Operation & Maintenance Manual. If the boom is not equipped with a boom lock the boom must be supported as described in the Operations & Maintenance Manual.

3. Securely block the wheels and disengage the parking brake.

Use the safety precautions listed in the appropriate Operations & Maintenance Manual: Operation & Maintenance Manual SEBU6865-01; Operation & Maintenance Manual SEBU 7017.

Installation of Purge Equipment And Procedure To Purge Service Brake Cylinder Group

1. Screw the modified cap with the purge equipment onto the machine's reservoir. Tighten until the seal of the cap makes contact, then turn an additional one-sixth of a turn. Fasten two lengths of tubing with the clamps. Place clear tubing (E), approximately 3.5 m (12 ft), into the hydraulic tank fill point. At least 250 mm (9.842 in) may be installed at the hydraulic fill point. Install the clear tubing so it does not move from the hydraulic fill point when under pressure.

2. Attach 6V-4144 Coupler Assembly (5) to pilot test port, at Hydraulic Control Valve. See Illustration 2. Refer to SENR5843-01, Systems Operation Testing and Adjusting TH62, TH63, TH82 & TH83 Telehandlers Hydraulic System, "Pilot Pressure Setting Check," Page 55. Fasten the tubing which goes to the horizontal brake reservoir fitting to the coupler assembly using a clamp as per Illustration 1.

NOTE: The Pilot Test Port may be identified by the hose marked "PS2" toward the disconnect fitting. The fitting may need to be angled slightly to accept the disconnect.

3. Attach a 6V-7830 Tetragage to point A as shown in Illustration 1.

4. Attach the remaining length of clear tubing to the 136-8537 Cylinder Assembly bleed screw. Place the other end of the clear tubing in the hydraulic tank fill point. At least 250 mm (9.842 in) may be installed at the hydraulic fill point. Purge the rest of the system in the following order: right rear axle bleed screw; left rear axle bleed screw; right front axle bleed screw; left front axle bleed screw. Be sure to install the clear tubing so it does not move from the hydraulic fill point when under pressure.

5. Start the machine's engine and allow the machine to idle.

6. Open the 1S-8937 Needle Valve (7) until the 6V-7830 Tetragage indicates 138 ± 35 kPa (20 ± 5 psi).

NOTE: The brake is activated with as little as 69 kPa (10 psi)indicated on the gauge.

7. Excess oil should flow directly into the hydraulic tank fill point. Pink oil flowing through the bleed point's clear plastic tube denotes entrained air in the oil. Allow the oil to flow from the purge location until the oil in the clear plastic tube becomes red.

NOTE: After purging each location tighten the bleed screw and replace the cap. Close the 1S-8937 Needle Valve. Turn the engine off and move to the next bleed point.

NOTE: Using equipment suitable for collection and containment of fluids, provide for the collection of purged fluids during this process. Obey all local regulations for disposal of all fluids.

8. Push the brake pedal in and hold down, loosen the tee fitting between the master cylinder and the booster cylinder and observe for entrapped air. Tighten the tee fitting, repeat if necessary.

9. Push in the brake pedal and hold down. Open the bleed screw on the booster cylinder to expel air entrapped in oil. Tighten the bleed screw and repeat if necessary.

10. At each axle bleed screw, open the bleed screw and pump the brakes numerous times.

NOTE: It may take 50 or more pedal strokes to expel all the air from each axle bleed screw.

NOTE: There is no need to close the axle bleed screw after each pedal stroke.

11. Remove the modified reservoir cap, all purge equipment and replace the original cap on the machine's 090-8957 Reservoir Assembly. Be sure to check the hydraulic oil level then replace the cap for the hydraulic fill tank.

Illustration 2. - 1. Pressure Reducing Valve. 2. Pilot Test Port.

NOTE: Pilot test port may also be called pressure test fitting.

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