BLEEDING BRAKE SYSTEM
CAUTION: Brake fluid is harmful to painted and plastic surfaces. If brake fluid is spilled onto a painted or plastic surface, immediately wash it with water.
Bleed hydraulic system whenever air has been introduced into system. Bleed master cylinder and brakes at all 4 wheels if master cylinder lines have been disconnected or master cylinder has run dry. Bleed brakes with pressure bleeding equipment or by manually pumping brake pedal while using bleeder tubes. Always bleed brakelines in sequence. See BLEEDING SEQUENCE.
NOTE: DO NOT allow reservoir to run dry during bleeding operation.
Master Cylinder Bleeding (Bench)
Support brake master cylinder body in a vise, and fill both fluid brake master cylinder reservoirs with brake fluid. Install plugs in front and rear brake outlet ports. Bleed front brake system first. Loosen plug in front brake outlet port and depress primary piston slowly to force air out of master cylinder.
Tighten plug while piston is depressed or air will enter brake master cylinder. Repeat procedure until no air bubbles are present. Repeat bleeding procedure for rear brake outlet port with front brake outlet plugged. Tighten plugs and try to depress piston. Piston will not depress if all air is out of master cylinder.
Master Cylinder Bleeding (On-Vehicle)
Using a line wrench, remove front brake tube and master cylinder outlet rear tube from master cylinder. Install short brake tubes in master cylinder and position them so they curve into master cylinder reservoir, and ends of tubes are submerged in brake fluid.
Fill master cylinder reservoir with clean brake fluid. Have an assistant pump brakes until clear, bubble-free fluid flows from both brake tubes. Remove short brake tubes and reinstall front brake tube and master cylinder inlet rear tube on master cylinder. Bleed each brake tube at master cylinder by having and assistant pump brake pedal 10 times and then hold firm pressure on brake pedal.
Loosen rearmost brake tube fittings until a stream of brake fluid comes out. Have an assistant maintain pressure on brake pedal until brake tube fitting is tightened again. Repeat procedure until clear, bubble-free fluid comes out from around tube fitting. Refill master cylinder reservoir as necessary. Repeat this bleeding operation at front brake tube fittings.
Fill brake master cylinder with new brake fluid. Loosen both wheel cylinder bleeder screws and leave them open until clear brake fluid flows. Check master cylinder reservoir fluid level often and do not let it run dry. Tighten wheel cylinder bleeder screws. One at a time, loosen caliper bleeder screws. Leave bleeder screws open until clear fluid flows. Check fluid level often. Tighten caliper bleeder screws.
Clean master cylinder cap and surrounding area. Remove cap. All models are equipped with dual-type master cylinder. Bleed primary and secondary systems separately. Loosen primary or secondary master cylinder hydraulic line fitting. See Fig. 1.
Fig. 1: Identifying Master Cylinder (Typical)
Courtesy of FORD MOTOR CO.
Wrap a cloth around brakelines to absorb escaping brake fluid. Slowly push brake pedal down to force out air. With pedal fully depressed, tighten fittings to prevent air from being sucked into master cylinder when pedal is released. Release pedal.
Repeat procedure until air is completely purged from master cylinder. When all air has escaped, tighten fittings with pedal down. Release pedal, and depress again. If pedal is not firm, repeat bleeding procedure.
Repeat procedure at bleeder fitting on rear anti-lock brake electrohydraulic RABS valve, each wheel cylinder and caliper. See Fig. 2. See BLEEDING SEQUENCE table under BLEEDING SEQUENCE. When bleeding is complete, fill master cylinder to proper level.
Fig. 2: Bleeding Wheel Cylinders (Typical)
Courtesy of FORD MOTOR CO.
CAUTION: DO NOT exceed 50 psi (3.5 kg/cm2 ) during bleeding.
Clean master cylinder cap and surrounding area. Remove cap. With pressure tank at least 1/2 full of specified fluid and charged at 10-30 psi (.7-2.0 kg/cm2 ), use adapters to connect tank to master cylinder. Follow equipment manufacturer's pressure instructions.
Open pressure bleeder valve. Bleed master cylinder primary and secondary hydraulic lines individually. Put shop towels in place to catch brake fluid.
Open lines. Allow brake fluid to flow out until all air is purged. Close bleed fitting and hydraulic line. Close pressure bleeder valve. Attach rubber drain hose to first wheel cylinder bleeder valve to be serviced. See Fig. 2. See BLEEDING SEQUENCE table under BLEEDING SEQUENCE.
Place other end of hose in clean glass jar partially filled with clean brake fluid so end of hose is submerged in fluid. Open pressure bleeder valve. Open bleeder fitting. Close bleeder fitting when fluid flow is free of bubbles. Repeat procedure on remaining wheel cylinder and calipers in sequence. See BLEEDING SEQUENCE table under BLEEDING SEQUENCE.
When bleeding operation is complete, close pressure bleeder valve, and remove tank hose from adapter fitting. Check brake pedal operation. Ensure master cylinder is full of fluid.
Before bleeding system, remove all vacuum from power unit by depressing brake pedal several times. Bleed master cylinder first, followed in sequence by rear wheel cylinders, anti-lock system components (if equipped) and calipers
BLEEDING HYDRO-BOOST UNIT
NOTE: Hydro-Boost is generally self-bleeding. Listed procedure will normally bleed air from system. Normal vehicle operation will remove any additional air.
Super Duty Pickup
Fill power steering pump reservoir with MERCON multipurpose automatic transmission fluid. Remove powertrain control module (PCM) fuse and crank engine for several seconds. Check and add fluid if necessary. Install PCM fuse. Start engine. Turn wheels from lock-to-lock twice.
Turn engine off. Depress brake pedal several times to discharge accumulator. Start engine, and turn wheels from lock-to-lock twice. If foaming occurs, stop engine, and allow foam to dissipate. Repeat lock-to-lock procedure until all air is removed from system
Wednesday, January 14th, 2009 AT 8:52 AM