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howdy guys,
I have a 2002 7.3 with roughly 415k miles. one owner, stock, except air intake and exhaust and always maintained properly. However, for the past ~ 10 months my brakes have not worked properly. when pushed, the pedal slowly goes all the way to the floor. No bounce back and i'm 100% positive there is no air in the lines. The master cylinder and hydro boost were replaced at 315k miles. All rotors and calipers are new. At first, I thought it was the master cylinder bypassing fluid so i changed it. (bench bled properly and all) no luck. It happened suddenly one time when i started the truck. has not gotten any better or any worse. No loss of fluid. I can bleed the brakes to where they are rock solid and as soon as you start the truck it goes back to the way it was. Any suggestions? My next best guess would be the hydro boost but im looking for some feed back before i go any further. Thank you in advance for your time.
very possible, this is the 3rd pump ive put in this truck. It is probably around a year old. The truck sits on 35's. I have never been able to turn the wheels with the truck sitting at a stop. even with stock tires. not sure if this is normal or not.
very possible, this is the 3rd pump ive put in this truck. It is probably around a year old. The truck sits on 35's. I have never been able to turn the wheels with the truck sitting at a stop. even with stock tires. not sure if this is normal or not.
Sounds like the pump. I'm running stock tire on mine and when The pump was going out I either had to put the truck on high idle or give it some RPMs to be able to turn the wheels at a stop.
Unless you have a fluid leak in the brake system the ONLY thing that can cause a sinking pedal is a bad master cylinder, a bad PS pump or bad hydroboost will give a hard pedal because you have low or no power assist. It is very possible that your replacement MC is bad, my record is 5 in a row before I got a good one for a customers truck. I now use only Cardone reman's although they can have problems as well, if I cannot locate an OEM NEW replacement.
Master cylinders can do that and there’s a lot of aftermarket new ones that bypass due to poor quality. The pressure supply (power steering pump) would only cause a hard pedal, the hydroboost can cause a number of weird events, but a sinking pedal isn’t one. The ABS unit can internally bypass a valve causing a sinking pedal while filling up its internal accumulator. There’s a simple If that’s the issue.
