Stiff Brake Pedal And Locks Up HELP!!!!!

[CaLa1450]

I've got a late 99' 7.3 and just recently my brakes have been locking up after I drive my truck for 15 minutes or more and at that time my brake pedal gets hard as a rock. I'm thinking master cylinder? I just recently cleaned front rotor pins and greased them. All rotors and pads are less then 8 months old. Any HELP would be greatly appreciated!

Chase

[mgassel]

Sounds like you could be having an issue with the hydro boost system. "Hard pedal"

A bad master cylinder would likely be no brakes.

The other issue you could have is contamined pads / shoes. If brake fluid or grease gets on the pads once heated may cause the same issue.

Have you checked the calipers do the pistons stick?

Trying to tell you about anything that could cause a problem.

My bet is the hydro boost problem but you need to verify that everything else is ok first.

Could be a bad brake hose.

[CaLa1450]

Pistons don't seem to be sticking. There is grease on the back of the pads from when I did rotor pins. What would be bad in the hydro boost system. THANK YOU for your help

ChaSE

[jesilvas]

Is it the ABS locking? I had a bad bearing, bent the ABS sensor, it would randomly lock up.

[mgassel]

Originally Posted by CaLa1450

Pistons don't seem to be sticking. There is grease on the back of the pads from when I did rotor pins. What would be bad in the hydro boost system. THANK YOU for your help

ChaSE

I not played with the hyrdo boost sytem too much so I could not tell you what actually goes out in them I just know it is possible.

Are you having any whinning noise or no power sterring while turning the steering wheel?

The other part of the hydo boost is your power steering pump if it is out of fluid or you have no power steering I would start there.

[CaLa1450]

Thanks for the replies guys.
No whining noise for the pedal or the powers stearing pump at all.
Both front wheel bearings are new with new abs sensors. My drivers side bearing ABS sensor was capped off before i replaced it. Maybe there could be dirt in the sensor? I'm not throwing any codes either. This is why I'm so confused haha. Thanks again for the help!

Chase