Brake problem

[77crewcab]

I have a 90 Caravan and the master cylinder went out, pedal to the floor leaking fluid at the master cylinder/power booster. I replaced the MC and have bled the brakes and it all is fine untill I start the van. Then I still have the pedal goig to the floor and the brake light is still on. Also getting a slight whoosh sound when pressing the pedal with the engine on. I guess it is possible that the booster might be bad as well but why can I not get pressure to build with the engine on?

[96Grand]

Master Cylinder Bleeding


On models with anti-lock brakes, turn ignition switch to Off position, then pump brake pedal a minimum of 40 times to de-pressurize hydraulic accumulator.
On all models, connect a suitable transparent hose to bleeder valve on right rear and submerge other end in a glass container partially filled with clean.
Pump brake pedal several times, then hold pedal down firmly.
With pedal firmly depressed, open bleeder valve of right rear brake until pedal fades to floor, then close bleeder valve.
Repeat procedure until a continuous flow of is released from bleeder valve. Ensure a fluid level is maintained in master cylinder at all times.
Perform Steps 2 through 5 for left rear, right front, and left front brakes in that order.
After bleeding of brakes is completed, road test vehicle to ensure brakes are operating correctly and pedal is solid.
Hydraulic Control Unit

Disconnect and isolate battery ground cable, then remove Hydraulic Control Unit (HCU) 10 -way and 2 -way connectors from bracket on lefthand strut tower.
Disconnect both connectors from wiring harness and HCU pigtail retaining straps from master cylinder brake tubing.
To prevent loss of from master cylinder, prop brake pedal in any position beyond first inch of travel.
Raise and support vehicle, then clean HCU thoroughly with suitable brake parts cleaning solvent.
http://www.alldatadiy.com/alldata/AFI~V6623531~C30621~R0~OB0~P3R0H~N/0/41746574/56417202/56417205/56419253/34853741/34861870/34862482/56243233/14626360/105667414/42407180

Remove four brake tubes from HCU valve block, then disconnect two master cylinder brake tubes at HCU.
Remove bolts securing HCU bracket to suspension crossmember, then remove HCU and bracket as an assembly. Carefully pull HCU wiring pigtail through retaining straps.
Reverse procedure to install, noting the following:


Do not use any bolts other than original or original equipment type to secure HCU mounting bracket to crossmember. Torque bolts to 21 ft. lbs.
Ensure four brake tubes are installed in correct positions on HCU valve block.
Torque all hydraulic line fittings to 12 ft. lbs.
Bleed brake system as described in this chapter, then road test vehicle to ensure ABS and base brake systems function properly.




Antilock Brake System Bleeding Procedures

The base brake system must be bled anytime air is permitted to enter the hydraulic system. However, anti-lock brake system components should only be bled if the hydraulic control unit has been removed or if there is reason to believe that air has entered the unit. The ABS portion of the braking system must be bled separately. Under most circumstances, only the base brake system will require bleeding; refer to Hydraulic System/Service and Repair for procedure. If the anti-lock brake system must be bled, proceed as follows:



Ensure all brake system components are installed and all hydraulic lines are connected securely.
Connect DRB diagnostic scan tool to diagnostic connector, then ensure Controller Anti-Lock Brake (CAB) has no stored diagnostic trouble codes.
Bleed base brake system as described in Hydraulic System/Service and Repair , then select "Bleed ABS" routine on diagnostic scan tool.
Apply firm pressure to brake pedal and initiate ABS bleed cycle one time, then release pedal.
Bleed base brake system once again, then repeat ABS bleed cycle and base brake system bleed until flow (as established in Hydraulic System/Service and Repair bleed procedure) is free of bubbles. Ensure all bleeder valves are closed tightly after bleed sequence is completed.
Road test vehicle to ensure base hydraulic system and anti-lock brake system operate properly.

Excessive Pedal Travel


Worn brake lining.
Pad knock back after cornering or rough road travel.
Piston or pad assembly not properly seated or positioned.
Air leak or insufficient fluid in system or caliper.
Loose wheel bearing adjustment.
Damaged or worn caliper piston seal.
Improper booster pushrod adjustment.
Pads out of flat more than 0.005 inch.
Rear brake automatic adjusters inoperative.
Improperly ground rear brake shoe and lining assemblies.

Vacuum Booster Replacement


With engine not running, pump brake pedal 4-5 times to deplete vacuum in power booster.
Disconnect both battery cables, then remove battery thermo guard and battery from tray.
Remove air inlet resonator and hoses as an assembly from throttle body and air cleaner housing.
On models equipped with speed control, disconnect wiring harness connector from speed control servo, then vacuum lines from servo and vacuum reservoir on battery tray.
Remove bolt securing speed control servo bracket to battery tray, then slide bracket forward to unhook it from battery tray and remove.
Remove battery tray, then proceed as follows:


Disconnect wiring harness connectors from EGR valve transducer, throttle position sensor and AIS motor.
Remove throttle body from intake manifold and clip attaching wiring harness to throttle cable bracket. Remove throttle body and throttle cable bracket as an assembly from intake manifold.




Remove vehicle wiring harness connector from brake fluid level sensor in master cylinder fluid reservoir.
Remove bracket for wiring harness connectors from studs on strut tower.
Clean area where master cylinder assembly attaches to booster using Mopar Brake Parts Cleaner, or equivalent solvent.
Remove clip attaching drain hose to brake tube at master cylinder. Remove drain hose from wiper module.
Remove master cylinder from vacuum booster and position aside. NOTE: It is not necessary to remove brake tubes from master cylinder when removing master cylinder from vacuum booster.
Remove EGR valve and vacuum transducer as an assembly from intake manifold.
Disconnect vacuum hose from check valve on booster. Do not remove check valve from booster.
Working under instrument panel inside vehicle, locate vacuum booster input rod to brake pedal attachment and position a small suitable screwdriver between the center tang on booster input rod to brake pedal pin retaining clip.
Rotate screwdriver enough to allow retaining clip center tang to pass over end of brake pedal pin, then pull clip off brake pedal pin. Discard clip and replace with new one during assembly procedure.
Remove Controller Anti-Lock Brakes (CAB) from vacuum booster mounting studs. Without removing wiring connector, position CAB aside.
Remove vacuum booster from dash panel by removing nuts under instrument panel.
Reverse procedure to install, noting the following:


Torque vacuum booster mounting nuts to 21 ft. lbs.
Ensure to use new retaining clip to connect brake pedal pin to input rod.
Torque CAB mounting bolts to 21 ft. lbs.
Torque EGR mounting bolts to 16-17 ft. lbs.
Install new vacuum seal when mounting master cylinder.
Torque master cylinder mounting nuts to 19 ft. lbs.
Torque wiring harness bracket mounting nuts to 7-8 ft. lbs.
Torque throttle body mounting bolts to 19 ft. lbs.
Torque battery tray mounting nut and bolts to 10-11 ft. lbs.

If you need anything else, let me know.

[77crewcab]

Thanks, got it figured out before you posted. Just had a lot of air left in the system.

[96Grand]

No problem, good to see you got it fixed. These brake systems sure can be a pain sometimes.

[protegechris]

Where can I find a suitable bleeder hose?

[protegechris]

Better yet, here's my issue. The pedal falls to the floor, very little pressure is built on the pedal. I opened both of the front bleeder valves when changing the brake pads, so I know there is air in the system.. just not sure what I need to bleed and where/how to do it.