Hello everyone,

I'm having a issue with one of our 199 powerstroke 7.3 trucks: when suddenly stomping on the brakes (emergency) the truck brakes VERY BADLY. To the point you allmost run into the guy in front of you, no matter how hard you're braking.
The pedal's hard, and the braking power is extremely bad.
However, when braking normally, and progressively, the brakes have a good bite. The ABS come on correctly when braking progressively all the way to hard.
This problem appeared rather suddenly.

When the brakes work well (after activating them progressively) you can hear a hissing-type noise from up front when you keep your foot hard on the brakes.


Truck's condition:
- New rotors and pads
- New powersteering pump and hoses, all bled correctly
- Brake calipers rebuilt
- New brake hoses at wheels
All work done over the past year and allways operated corretly. And now this wierd problem.

Brakebooster is still original (truck's 1999).

Is this an indicator that my brake booster's going out?
Or may there be an issue with the ABS unit and the check valves?
Any ideas?

Thanks- Eug

 

Use a Mighty-vac hand pump to check if the booster holds vacuum.

 

99 superduty powerstroke has hydroboost brakes, not vacuum. it sounds to me like the brake booster is failing.