I recently bought new tires for my 2001 sport and the mechanic informed me i needed new brakes all the way around because they were in bad shape so i continued to drive for a couple of day because i had not even noticed a difference in my brake pressure but sure enough the brakes were gone so i had my personal mechanic install new calipers, drums, rotors and pads all the way around and after bleeding the brakes a few times, there was even less pressure on the brake pedal than with the all the worn out parts on it. My mechanic told me that my master cylinder was the problem so i just replaced the master cylinder last week but after bleeding there was more resistance in the pedal than before the master cylinder was put in but it was still very spongy, i dont suspect a leak in any of the lines. Someone please help

 

I would suspect a leak. The brake line going to the rear is notorious for rusting out. It will weep initially, until if finally just blows out. Trouble is, fluid doesn't hit the ground right away. It breaks back by the gas tank, where you simply cannot see it....

That said, if it ain't leakin', then there is still air in the line somewhere.

 

The second gen trucks are very old now (about 20+ years old) and leaks pop up in the metal brake lines. Also check the line going to the passenger side front brakes, as it tends to develop leak with age, too. If you plan to keep the truck a while, its a good idea to replace all of the metal brake lines, especially the rear line feeding the rear brakes that runs along the frame. It seems to almost always be the first line to break.