I have a mushy brake pedal, I think that the master cylinder is the culprit, truck has a new PS pump and has been flushed afterwords

the wierd thing is that occasonaly my brake pedal will be nice and firm like it should and I have excellent stopping power, if I pump the pedal it will be a little more firm then sink back down, but at random times I can hit the brake pedal and it can be firm and perfect

so before I do the master I was wondering what someones opinion might be toward this along with some common symptoms of a failing hydrobooster

 

Sounds more like a failing MC or brake hose.

Hydroboost failure would make your pedal hard to push.

 

How many miles have you put on the truck since you replaced the PS pump? Hydroboost units can be a pain to bleed. I'd check your lines running from the pump to the HB unit as any loose connections can cause the unit to suck in air pretty quick.

 

I've checked all lines

been about 3k miles since I put on the new PS pump

only leak in the system is a drip overnight from where the pressure line goes into the PS pump

 

Powerstroker100, do you have any noise from the brake system that you can hear in the cab when on the brakes? Ever since I replaced my power steering pump my has a rattle when I am sitting at a light with the brakes on. Not trying to hijack just wondering if my truck is going that route also.

 

no, unless I really push it to the floor then I can hear the pump whine a bit

 

I have this exact issue in my truck did anyone ever diagnose the rattle sound when sitting stationary?