'88 toyota pickup breaks?

[Thomas V]

engine off breaks work fine. engine running and you stomp on them they are fine. under normal pressure they go almost to the floor, and feels like there is no vacuum assist, but still stop the truck just fine. i bleed the system, and put new pads on and checked all wheel cylinders for leaks. no lines are leaking, and no vacuum leaks. and the vacuum check valve works fine. could it be the master cylinder?

 

[zzigzzag420]

if you have no vacume assist the pedal will be hard as a rock. check your rear brake adjustment if you have no air in the system and your master cylinder is good then it could be that the rear brakes are out of adjustment. have a professional help you out if possible

 

[Junior]

If this is a 4x4 truck,there is a proportioning valve in the rear that has a bleeder valve on it. This valve will adjust braking power to the rear depending on the load in the bed. It does this by a rod that is connected to the rear axle and the valve that is connected to the frame. When the rear of the truck is loaded and squatting in the rear,there is more pressure for the back brakes. This also keeps the truck from skidding when unloaded.
Anyway,there is a bleeder screw on this valve,and there is probably air in the system at the valve. I did a brake job on a truck like this and it took forever to bleed out until I found this bleeder screw.