Hi, new user here! I have a 97 caravan slight issue is when at low rpm braking the brake pedal is soft. Bled all 4 brakes come to find out both rear brake cylinders boot were cracked so replaced them, now l/r rear cylinder is not getting any brake fluid. So I traced the line back, opened it at proportioning valve no fluid coming out of there, so I go back further and take the line that goes from master cylinder to the junction block and take the line out and the fluid is coming out when I depress the pedal. Now I was saying if I replace the junction box and just run the back 2 lines straight to the wheel cylinder will I have any problems? Here is what it looks like stock.



what i'm talking about is :
skipping the proptional valve and just make straight lines??



Any inputs would be great please, thanks for your time.

 

usually it's the height sensing proportioning valve that goes bad, not the junction block. The junction block it just a splitter, I would assume you need the proportioning valve or you'd get too much pressure to the rear brakes. Here' s a service manual write up..........


HEIGHT SENSING PROPORTIONING VALVE

CAUTION: The use of after-market load leveling or load capacity increasing devices on this vehicle are prohibited. Using air shock absorbers or helper springs on this vehicle will cause the height sensing proportioning valve to inappropriately reduce the hydraulic pressure to the rear brakes. This inappropriate reduction in hydraulic pressure potentially could result in increased stopping distance of the vehicle.
On vehicles not equipped with ABS brakes, the brake systems hydraulic control unit (HCU) is replaced by a junction block. The junction block is made of aluminum and is mounted to the front suspension crossmember on the drivers side of the vehicle in the same location as the (HCU) on an ABS equipped vehicle. The junction block is permanently attached to its mounting bracket and must be replaced as an assembly with its mounting bracket. The junction block is used for diagonally splitting the brakes hydraulic system.
Vehicles not equipped with ABS brakes use a height sensing proportioning valve. The height sensing proportioning valve is mounted on the left frame rail at the rear of the vehicle. The height sensing proportioning valve uses an actuator assembly to attach the proportioning valve to the left rear spring for sensing changes in vehicle height.
HEIGHT SENSING PROPORTIONING VALVE OPERATION

The height sensing proportioning valve regulates the hydraulic pressure to the rear brakes. The proportioning valve regulates the pressure by sensing the load condition of the vehicle through the movement of the proportioning valve actuator assembly. The actuator assembly is mounted between the height sensing proportioning valve and the actuator bracket on the left rear leaf spring. As the rear height of the vehicle changes depending on the load the vehicle is carrying the height change is transferred to the height sensing proportioning valve. This change in vehicle height is transferred through the movement of the left rear leaf spring. As the position of the left rear leaf spring changes this movement is transfer through the actuator bracket to the actuator assembly and then to the proportioning valve.
Thus, the height sensing proportioning valve allows the brake system to maintain the optimal front to rear brake balance regardless of the vehicle load condition. Under a light load condition, hydraulic pressure to the rear brakes is minimized. As the load condition of the vehicle increases, so does the hydraulic pressure to the rear brakes.
The proportioning valve section of the valve operates by transmitting full input hydraulic pressure to the rear brakes up to a certain point, called the split point. Beyond the split point the proportioning valve reduces the amount of hydraulic pressure to the rear brakes according to a certain ratio. Thus, on light brake applications, approximately equal hydraulic pressure will be transmitted to the front and rear brakes. At heavier brake applications, the hydraulic pressure transmitted to the rear brakes will be lower then the front brakes. This will prevent premature rear wheel lock-up and skid.
The height sensing section of the valve thus changes the split point of the proportioning valve, based on the rear suspension height of the vehicle. When the height of the rear suspension is low, the proportioning valve interprets this as extra load and the split point of the proportioning valve is raised to allow more rear braking. When the height of the rear suspension is high, the proportioning valve interprets this as a lightly loaded vehicle and the split point of the proportioning valve is lowered and rear braking is reduced.

 

well for not i'm going to replace almost all the brake lines since they are corroded to ****. After that i'll bleed them and see where to go from there. Thanks for your time.