I have a '90 F-150, when I step on the brakes, the pedal makes a swoosh sound and goes half way down before anything happens. The truck stops fine, just takes an extra second for the brakes to engage. The pedal will go to the floor if you push hard enough but doesnt sink if you apply the same pressure. I've replace the rear pistons, shoes and drum, and front rotors and pads, and master cylinder. I am told that if the pedal doesnt sink, then the master cylinder is fine. And if the pedal isnt too hard then the booster is fine. There is no leaks and I have bleed at least a gallon through the system. Both rear and front brakes engage fine. Could there be a problem anywhere from the actual pedal to the booster?????

 

There is an adjustment on the booster pushrod. Did this happen to get move when you changed the MS. The swooshing sound is usually a leaky/shot power booster. When I changed my booster and MS I did not have the pushrod adjusted properly and the pedal would travel half way down before the pushrod engaged the MS.

Just a thought.

 

The swoosh noise is normal. All ford trucks do it. It's like the power steering whine.

As for the low pedal, I would start by making sure your rear brakes are adjusted. You should be able to feel the shoes drag slightly all the way around when you spin the wheel by hand.

 

Thanks for the replies... yes I did adjust the pushrod in the booster as far out as it would go without pushing in on the master cylinder, the brakes are very tight on the back, probably too tight. ( I could barely get the drum on) I just replaced the rear rubber brake hose, that seemed to help the rear brakes work a little better but didnt do anything with the pedal feel. Tomorrow I'll change the booster and front rubber brake lines. That leaves the calipers, metal brake lines, and the RABS(module?) as the only things that havent been replaced. Im begining to think that andym is right in that it is just normal, but the pedal doesnt feel anywhere near like any other trucks or cars Ive driven. The '97 f-150 I drive feels firmer and you dont have to push it near as far for it to do something. ( I realize its a totally different vehicle but thats the closest thing I have to compare it to)