I have a 94 f150 4x4, and yesterday while braking at a stop sign, I heard a single popping sound. Now my brakes are very spongy and it takes a complete pressing of the brake pedal to get the truck to stop. I dont see any fluid on the ground, so I dont think a line burst. It sounded like the pop came from behind the cab, but I cant be for sure. Any ideas where I should be trouble shooting? Thank you

 

check the brake rods under the dash, and look for any signs of fluid there.

 

Check behind your wheels? Maybe you blew a wheel cylinder or caliper.

 

Check your fluid level first to see if your loosing any. Pull your wheels and do a visual. Look for any fluid or broken springs. Anything out of place. Pump your brake pedal with the engine off to eliminate vacuum in the booster, then press the pedal down. Watch to see if the fluid goes up and down as you work the pedal. If so your master cyl seal is bad. If your good, pump up till you get pressure then release quickly. If you get a big squirt of fluid back you have air in the lines. Any brake /ABS light on?

 

Check yer radius arm bushings. Mine did the same thing after all new brakes (needed them anyway), checked my bushings. and the radius arm brackets were wore out. PITA job, but no more noise. plus handles alot better!

 

Sorry for not commenting for the last 2 weeks. I work a job 2 weeks on and 2 weeks off. Anyways, I pulled the drivers side rear drum off and found that I had broke the lower spring that goes to the brake pad and the emergency brake. I bought a kit to replace all the springs and installed new pads. IT works like a champ now. Thanks for all the comments.