WHEN COMING TO A STOP I GET A PULSING ON THE FRONT BRAKE WITH A NOISE AND A SOFTENING OF THE BRAKE.
IT DOESN'T HAPPEN AT HIGH SPEED BRAKING.(SENSOR?)
THIS IS A 2000 JIMMY 4+4 187,000 kms BOTH FRONT...
The pulsing is usually caused by a warped rotor. Rotors warp from quick stops and rapid braking techniques. It could also possibly be a weakening Master cylinder or a leaky diaphragm in the brake boost, but this last would be accompanied by a hissing sound when you hit the brakes. To check the rotors, block the rear wheels and raise the front until the wheels are off the ground. Spin the wheels individually by hand slowly - they should roll smoothly. If they do , have a helper apply very light pressure to the brake pedal with the engine running and again spin the wheel. With the wheel spinning, have the helper apply increasingly more pressure to the brake pedal until it stops the wheel from turning. Now have them back off the pedal slightly so you can spin the wheel again and spin, looking for uneven rolling. Check both front wheels to show which rotor is warped. If either is warped, you'll need to have the rotors resurfaced ( turned) and replace the pads both sides.
If they turn smoothly through all of the tests, apply solid pressure to the brake pedal until you can't push it any farther and hold that pressure. Watch the pedal for sinking. If it sinks, then you either have air in the system or a bad Master cylinder. Bleed the brakes first before you replace the master and do the pressure test again. If you don't find anything at this point, start the engine and do the brake pressure test again. If the pedal sinks, then you may have a vacuum leak in the booster and will need to do a vacuum test on the booster to make sure, since that job is usually hard to do and may be costly, depending on the style of booster you have.
Hope this helps!!
Dec 10, 2010 |
2000 GMC Jimmy