i have replaced the master cylinder, and both front calipers, and new pads, and turned rotors last week on my truck, and still a soft pedal. was bled properly, and MC was bench bled and bled again on the truck.

I was wondering could it be the check valve on the brake booster, or the hose going to the manifold from the check valve? that hose looks like its dry rotted.

its on a 98 4.6 4x4, and what would be a symptom of that check valve going bad or being stuck open?

 

That hose doesn't or shouldn't go to the manifold. Your PCV connects to the manifold. Booster hose connects to very bottom port on the plenum (body elbow).

The hose that deteriorates is a emissions hose that is at the very top of the plenum and connects to a green 90* elbow.

The check valve is plugged directly into the booster, - left side. Yes, those do get bad.

If you search "soft pedal" within this forum or across the board, I bet you'll find exactly the info wanted. I've seen soft pedal threads.

 

nope, not possible.

If you have a vacuum leak in the hose or the check valve then you would have a hard pedal, not a soft pedal.

Lack of vacuum will always make the pedal hard.

To see this, shut off the truck and then pump the brake pedal 5-8 times. It will get rock hard once the vacuum is gone.