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Re: 92 explorer brake issues
Here is a diagram of your brake system with instructions on how to bleed this particular system: (Picture 1 a)
When any part of the hydraulic system has been disconnected for repair or replacement, air may get into the lines and cause spongy pedal action (because air can be compressed and brake fluid cannot). To correct this condition, it is necessary to bleed the hydraulic system after it has been properly connected to be sure all air is expelled from the brake cylinders and lines.
When bleeding the brake system, bleed one brake cylinder at a time, beginning at the cylinder with the longest hydraulic line (farthest from the master cylinder) first. ALWAYS Keep the master cylinder reservoir filled with brake fluid during the bleeding operation. Never use brake fluid that has been drained from the hydraulic system, no matter how clean it is.
It will be necessary to centralize the pressure differential value after a brake system failure has been corrected and the hydraulic system has been bled.
The primary and secondary hydraulic brake systems are individual systems and are bled separately. During the entire bleeding operation, do not allow the reservoir to run dry. Keep the master cylinder reservoir filled with brake fluid. (Picture 1)
Clean all dirt from around the master cylinder fill cap, remove the cap and fill the master cylinder with brake fluid until the level is within 1 / 4 in. (6mm) of the top edge of the reservoir.
Clean off the bleeder screws at all 4 wheels. The bleeder screws are located on the inside of the brake backing plate, on the backside of the wheel cylinders and on the front brake calipers.
Attach a length of rubber hose over the nozzle of the bleeder screw at the wheel to be done first. Place the other end of the hose in a glass jar, submerged in brake fluid.
Open the bleeder screw valve 1 / 2 - 3 / 4 turn.
Have an assistant slowly depress the brake pedal. Close the bleeder screw valve and tell your assistant to allow the brake pedal to return slowly. Continue this pumping action to force any air out of the system. When bubbles cease to appear at the end of the bleeder hose, close the bleeder valve and remove the hose.
Check the master cylinder fluid level and add fluid accordingly. Do this after bleeding each wheel.
Repeat the bleeding operation at the remaining 3 wheels, ending with the one closet to the master cylinder. Fill the master cylinder reservoir
Master Cylinder Replacement Proceedures.
With the engine turned off, push the brake pedal down to expel vacuum from the brake booster system.
Disconnect the brake fluid level sensor wire from the reservoir.
Disconnect the hydraulic lines (use correct tool, a Line Wrench) from the brake master cylinder.
Remove the brake booster-to-master cylinder retaining nuts and lock washers. Remove the master cylinder from the brake booster.
Before installing the master cylinder, check the distance from the outer end of the booster assembly push rod to the front face of the brake booster assembly. Turn the push rod adjusting screw in or out as required to obtain the length shown.
Position the master cylinder assembly over the booster push rod and onto the 1 studs on the booster assembly. Install the attaching nuts and lockwashers and tighten to 13-15 ft. lbs.
Connect the hydraulic brake system lines to the master cylinder.
Bleed the hydraulic brake system (refer to procedure in this Section). Centralize the differential valve. Then, fill the dual master cylinder reservoirs with DOT 3 brake fluid to within 1 / 4 in. (6mm) of the top. Install the gasket and reservoir cover. Roadtest the vehicle for proper operation.
When replacing the master cylinder it is best to BENCH BLEED the master cylinder before installing it to the vehicle. Mount the master cylinder into a vise or suitable equivalent (do not damage the cylinder). Fill the cylinder to the correct level with the specified fluid. Block off all the outer brake line holes but one, then, using a long tool such as rod position it in the cylinder to actuate the brake master cylinder. Pump (push tool in and out) the brake master cylinder 3 or 4 times till brake fluid is release out and no air is in the brake fluid. Repeat this procedure until all brake fluid is released out of every hole and no air is expelled.
Last edited by octaneman; 06-29-2009 at 12:14 PM.
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