BRAKE PEDAL SYMPTOMS
1. If you recognize the symptoms of brake trouble, it's easy to pinpoint the problem. For example, the brake pedal can
tell you a lot about the condition of the brakes.
2. Put your foot on the pedal. It should drop about 1/4-inch or so under the weight of your foot. That's called free travel.
While you're doing this, also check the action of the pedal return spring. If you push the pedal down and it doesn't snap
back when you release it, there's a problem with the spring or linkage. It must be checked out.
HMMWV's and CUCV' have a hydro-booster that lets the pedal sink if you apply steady, hard
pressure while stopped. This can be misleading, so check out the brakes if the driver reports it.
3. The pedal should be firm once you pass the free travel on most trucks. A sinking brake pedal is the sign of a leak. If
you can't find a leak, and the fluid in the master cylinder stays up, the master cylinder may be defective.
4. A spongy or soft pedal means there is air in the lines. Air gets trapped when the fluid level drops too low in the
master cylinder, or the brakes were not bled properly the last time they were serviced, or there is a leak.
Bleed all the lines and pump the brakes several times. If the pedal starts to soften again, there is a leak.
6. A spongy pedal can also mean a hose has become weak and is ready to burst. Brake hose inspection is required at
each semiannual service, but don't wait if you have a spongy pedal.
7. Replace any hose with a bulge. Look close at the hoses that run near the frame. Check each hose for wear or
pinching. If a hose is worn or cracked through the outer cover down to the first layer of fabric, or if it's crimped, replace the
8. Additional information on mandatory brake hose inspection can be found in TB 9-2300-405-14, Mandatory Brake
Hose Inspection and Replacement-Tactical Vehicles.