I have a 2000 ford excursion that I bought 2 weeks ago and I had to replace brake pads and rear driver side Caliper. Since then the brake pedal has been soft and i have bled the system. So I then replaced the master cylinder and bench bled and bled the brakes again with no luck. I've notice when truck us off it is hard but once the truck is on its soft and goes to the floor. If I pump the pedal while I. Park it firms up but once I drive it the pedal is back to the floor. Truck stops but takes time. What can it be? It's a 2000 excursion 2wd 6.8 v10 with 253,000 mile

 

Any visible leaks? I would start there.... Then, look at the brake soft lines. They do weaken over time and expand too much.

 

Looked at the lines today had brake applied while I felt and looked at them and nothing. No leaks.

 

It's internal, you won't see it on the outside. The inner plies break down over time, which results in little flaps and small channels for fluid to accumulate. The flaps can also get wedged open by the fluid flow, acting as a passive check-ball resulting in random brake symptoms or squishy pedals.

I take it you had zero issues prior to relaxing the caliper?

Did you do both, or just one caliper? Reason I ask is it is widely regarded as the better route to do both sides of an axle when doing brakes - but hey, we all have budgets sometimes!

Thirdly - are you 100% positive the parts store gave you the correct caliper? The reason I ask is left and right look exactly identical, except the bleed screws are on different ends. Your bleed screw is on top, correct? Just asking because I myself have overlooked that, as well as several other people.

 

No just one side Caliper was replaced. The caliper was one off a truck from the junk yard. No issues until I replaced brake pads and caliper. I didn't buy a new one cause at the time I didn't want to buy one new for one side.

 

That may be your issue then. Caliper integrity is possibly compromised resulting in internal leaks or air pockets. Brakes are one of two things I'd never second-hand, steering being the other.

 

I will replace the the caliper with a new one tomorrow and update you guys on that.

 

Should really change both if you can.

 

Agreed. Doing one side isn't the best way to approach brakes on any vehicle. Rear calipers are not that expensive.

 

As Krazee Matt asked earlier is the bleed screw on the caliper you replaced on top????
There were several different brake set ups with the same calipers in different orientations and it is very common to get one with the bleed screw not on top as its orientation is relative to the particular brake set up on the axel and will end up on the upside down on the wrong axle..... Been there done that.