I have an 01 Supercrew 5.4 and about a week ago the brake pedal started to get soft at times. If i'm going to stop at a light the pedal is soft doesn't go all the way to the floor but is soft, then if I let go and pump again its hard. I was thinking either master cyl. or brake booster? Any one had this problem before?

 

Sounds like you need to bleed 'em. Flush all the way through with brand new fluid if you've never done it before. Search the forum for details.

 

"about a week ago the brake pedal started to get soft AT TIMES" Sounds like a classic case of a master cylinder gone bad.

 

master cyl, or you're low on brake fluid (which should cause the amber brake warning light)

 

BLEED FIRST
if that doesn't fix it, then replace the MC.

yes, he says "at times" but then he says that when he double-pumps it is hard, implying that its only then that its not a soft pedal.

So it could still potentially be fixed with a bleed.

But either way - take it easy till you know its good... don't want to hit someone in the meantime...

 

That's what I'm talking about. The OP didn't indicate they had done any maintenance in the area yet, so I usually recommend the simplest/cheapest thing first.

Then if you've still got problems you can go on to more troubleshooting. Don't just replace the master cyl. because you've got a squishy pedal. When your truck gets a misfire, do you buy a new engine? No, you try replacing the spark plugs first.

Master cylinder is a good place to go if bleeding doesn't fix it, though.

Good luck!

 

Thanks to all that replied I'll try bleeding the brakes first then go ahead from there!