Last week while at the beach I felt my brakes begin to get "mushy" the pedal travelled much farther than normal to apply the brakes. I checked my brake fluid and it was fine so I took the truck to the mechanic that last worked on the brakes when I got home. He believed it to be the master cylinder and he put 3 different ones on it with no improvement. He re-installed my original master cylinder. He cannot find any leaks in the vacuum system and I don't have any warning lights on on my dash. I found some references to some problems with the ABS relay but after looking through my manual I can't find where it is located. Does anybody have any ideas what the problem could be?

 

I am by NO MEANS an expert on this, but had some brake issues on my '02 so i've done some reading around here. My ABS messed up, so i simply removed the fuse in the engine bay box (just look in the manual). If you think it might be ABS, just remove the fuse, if it fixes the problem - good...if not, pop it back in.

You may also want to check the state of the lines - i read in a post by jbrew that they can bubble or something and thus effect the pressure.

If the master cylinder is fine, finally i would look at the booster (which i would assume your mechanic did anyways). There's a method on testing it in your Hayne's manual.

May have already done all that stuff, but that's the extent of my knowledge!