The wife and I were running some errands yesterday,I had been having one of those days where everything that could go wrong did ,my wife just thought I was in a bad mood, when I picked up my sunglasses to put them on and a lens popped out, I told her "See thats the way everything has been going today,we better get home before the truck breaks down." Well I guess she"the truck" heard me because a half a mile later at a redlight ,there were a few cars in front of me and we hear a LOUD snap and all of a sudden the brake peddle goes straight to the floor ,to keep from hitting anyone I whip it into a gas station parking lot and the whip it back to the left to avoid the gas pumps and finally coast to a stop.
Needless to say you could'nt fit a greased dime between my *** cheaks.
Now I'm thinking I just popped a break line but there was no brake fluid anywhere ,so I turn the truck on and the brakes pumped right back up as if nothing ever happened,now you can step on them and thier fine .I drove home and when we got on to our street I tried slaming them on and they work fine.I cant figure out what the snap was and there are no wierd noises at all now she drives and stops fine .Has anyone ever had this happen or should I call a priest?

 

This is toooo dangerous to not get it checked out. I would take it straight to a break place that gives free inspections and tell them what happen.

 

It am not sure, but it sounds like the power brake booster could be bad. There is a seal in them that can give way and cause the pedal to drop. Is the fluid level good? If you can not detect a leak then I would tend to think that could be the problem unless you had a serious air pocket in the lines.

 

I have seen something like this before on a f-150.
Check were the power break booster bolts onto the firewall.
Is the firewall damaged cracked ?
That pop sound might have been the firewall cracking.
The Truck is very dangerous the way it is.
Dont trust it.
Have someone pump the breaks while you look at the booster.

 

I'm with MinnMan on this one. The brake booster/master cylinder may have pulled free of the firewall mounting.

 

well if the brake booster went out it wouldnt go to the floor, it would be really hard

 

I have had a brake booster go out twice before and it will hiss really bad and the pedal will drop. At least this is what happened in my case.

 

but a faulty brake booster would never cause the pedal to drop to the floor...all the brake booster does is make it easier for you to apply the brake