Brake Pedal goes to the floor

Tiny
EBELL65@VERIZON.NET
  • MEMBER
  • 1989 FORD F-350
Brakes problem V8 Two Wheel Drive Automatic 275000 miles

Hello,

I have a 1989 F350, 2 wheel drive dually, 460 ci gas motor. I have recently had the brakes done, front and rear pads, rear brake cylinders. The pedal has always been soft. I recently replaced the Master cylinder. I bench bled the MS before installing it. It appeared to be firm. I bled the wheels until no more air came out (went thru 4 bottles of brake fluid). The brake pedal goes right to the floor. Is there an ABS valve that needs to be bleed, if so where is it?

What else might lead to this condition. There are no leaks on the system. Everything is dry, but the pedal goes right to the floor with very little braking power.
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Sunday, November 23rd, 2008 AT 9:50 PM

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Tiny
DAVE H
  • EXPERT
Sounds like you still have air in the system if there are no leaks .. like ras has said could be master cylinder faulty seals ? try bleeding master cylinder again while on vehicle ?? see if it improves pedal

Here is the proper way to bleed and brake master

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

MASTER CYLINDER BLEEDING
NOTE:Master cylinder can be bled on vehicle or by using bench bleeding method.

On Vehicle Bleeding
Loosen one line nut on master cylinder. Wrap shop cloth around tubing below bitting to absorb escaping brake fluid. Depress brake pedal to floor by hand and hold. Tighten fitting.
Release brake pedal. Do not release pedal until fitting is tightened or air will re-enter master cylinder. Repeat procedure until air no longer escapes from master cylinder. Repeat process for other line and ensure that brake pedal is firm.
Bench Bleeding
Clamp master cylinder in vise by mounting flange. Install plugs in outlet ports. Fill reservoir with clean brake fluid. Loosen plug in rear port. Slowly depress piston slowly to force air from cylinder. Without releasing piston, tighten plug in outlet port.
Repeat process until no air is released from port. Bleed front outlet port(s) using same method until all air is removed from cylinder.
MANUAL BLEEDING
NOTE:DO NOT allow master cylinder to run dry during bleeding. NEVER reuse brake fluid that has drained from brake system. When bleeding disc brakes, air may tend to cling to caliper walls. Lightly tap caliper while bleeding to aid in removal of air.

Attach bleeder hose to right rear wheel cylinder and submerge end of hose in container partially filled with clean brake fluid. Loosen fitting about 3/4 turn and slowly depress brake pedal fully. Close bleeder and release brake pedal.
Repeat until fluid is free of air bubbles. Repeat process for remaining cylinders following proper bleeding sequence. See BLEEDING SEQUENCE table. After completing bleeding procedure, ensure brake pedal is firm.
PRESSURE BLEEDING
NOTE:NEVER reuse brake fluid that has drained from brake system. Ensure bleeder tank has sufficient fluid to complete bleeding procedure. DO NOT exceed 50 psi of pressure in tank.

On power brake equipped vehicles, release vacuum from booster by depressing brake pedal several times. Clean master cylinder cap and surrounding area. Remove cap. With pressure tank at least 1/2 full, connect to master cylinder with adapters. Attach bleeder hose to right rear wheel cylinder.
Place other end of hose in clean container partially filled with clean brake fluid so end of hose is submerged in fluid. Open release valve on pressure bleeder. Follow equipment manufacturers pressure instructions unless noted below.
Unscrew bleeder valve 3/4-1 turn noting fluid flow. When fluid flowing from cylinder to jar is free of bubbles, close bleeder valve securely. Repeat process following proper bleeding sequence. See BLEEDING SEQUENCE table.
PRESSURE BLEEDER SETTINGS
ApplicationPsi (kg/cm2 )
All Models(1) 10-30 (.7-2.0)
(1)NEVER exceed 50 psi.

BLEEDING SEQUENCE
ApplicationSequence
W/O Rear Anti-Lock Brakes....RR, LR, RF, LF
W/Rear Anti-Lock Brakes(1)... RR, LR, ABS Valve, RF, LF
(1)ABS valve is located on frame rail ahead of rear axle.Valve is bled in same manner as wheel cylinders.

BRAKE SYSTEM BLEEDING
HYDRO-BOOST SYSTEM BLEEDING ("F" SERIES SUPER DUTY)
Fill power steering pump reservoir with Motorcraft MERCON multipurpose automatic transmission fluid. Crank engine several seconds with coil wire disconnected. Check and add fluid if necessary. 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.
NOTE:Hydro-boost is generally self-bleeding. Listed procedure will normally bleed air from system. Normal vehicle operation will remove any additional air.
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Monday, November 24th, 2008 AT 5:50 AM

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