I have a 1996 F350. I was having a soft pedal about 6 months ago so I replaced the vacuum pump, brake booster, master cylinder, rear wheel seals, rear brakes, etc. Well a couple of weeks ago the vacuum pump went bad. I replaced that again and I was having an issue with the pedal going down fine the first time, but it you tried to brake again the pedal was hard to push down. I replaced the brake booster as well thinking that maybe the issue and it was not. I bleed the hell out of the brakes and that is not the issue either. Any other ideas? Like I said brake pedal works fine the first time and as long as you drive a ways before braking again it works, but if you have to brake quickly you literally have to stand on it to get it to stop. Thanks.

 

Sounds like you got a bad VP

 

Did you replace your booster with a zero loss booster?

It might be possible you have a vacuum leak someplace, and thats the cause of your pump working a bit to hard and it going out.

 

does the brake light in the dash come on? sounds like not enough vacuum to me

 

Thanks for the reply. As a matter of fact the brake light in the dash does come on.