1993 f250 pick up 7.3 non turbo auto trans.

we replaced the front calipers new pads, rotors in the future

we replace rear wheel cylinders, brake shoes

we replaced a few brake lines and bleed everything twice


there is a new master cylinder we didn't do and not sure it was bench bleed or not and if it matters at this point.

so the brake pedal feel is spongy like we got something but then we don't. we can stop but the pedal doesn't stop if you hold pressure if goes to the floor.

now what all those things are connected to the brake booster . the brake booster line goes to some bar with all these other lines plugged in. one goes to a black hockey puck thing with an electrical harness the other ones goes to some flying sauce pump thing on top of the engine and and small line goes over to a 3 way split near the passenger firewall heater box area.

HELP!!!!!!!! haha cant wait to hear all the good info

 

Mine does that too. I've never floored my brake pedal unless im testing it in the drive way. Its stops well on the road and I dont notice it bleeding down. Im looking forward to seeing your fix.

 

What you're describing is the vacuum system. The vacuum pump supplies vacuum (since a diesel engine does not produce vacuum as part of its intake process). There's a vacuum line to a distributor box, which just breaks out the vacuum supply to various components. It splits off to the HVAC controls (on A/C equipped trucks), the brake booster, and that vacuum dashpot thing you see on the fender well. TBH I don't know what that's for; I figured the old C6s might use it somehow, but we've got a T19 and we still have it. I'll have to check the EVTM tonight just to slake my curiosity.

Probably not a vacuum issue anyway. If you had a vacuum problem, you'd have a perpetually hard pedal (no boost).

First thing you should do is bleed the M/C, then re-bleed the lines to the wheels, just to eliminate the uncertainty about the bench bleeding. If the problem persists, esp. if it's a case of fairly good pressure initially, but then the pedal dropping even as you're stopped, holding the pedal, that's a characteristic of the Ford brake boosters. Not sure if this applies to the IDIs, but for the PSDs, they offered what is called a "zero loss" booster, one that provides the same boost initially, but doesn't do that pedal drop as you hold it.

 

If you have a low or spongy pedal it's air in the sysytem. If you have gradual bleed off it's your master cyclinder. A low pedal can also be caused by your rear shoes out of adjustment. If your e-brake is low also your shoes need adjustment.

 

we are gonna try and make sure there is no air trapped in master cylinder then go from there