My brakes in the front keep locking up. My question is what could this be the cause of? I have changed all brake pads, calipers and hoses to the front brakes. I did a complete change of the rear drums and boots. Tried to drive the car to see if it worked correctly and the car went about 3 miles and wheels locked up in the front again. Then changed master cylinder, bled all lines. Still brakes go and then lock up. When i press the brake pedal its stiff and i dont have that play in the pedal like i used to. It feels hard to push and not sure what to do. Someone told me thats a mechanic that it might be my brake booster. Any ideas?

 

Hard pedal is indicative of a bad booster.

Put your jack and stands in the vehicle and drive it until it locks up again. Leave it running, jack up the front of the vehicle and turn each wheel by hand. If they're dragging, turn of the engine and pump the pedal to relieve the vacuum in the booster, then spin the wheels by hand again. If there's no wheel drag the booster is bad.

 

so I jacked up the car, turned the wheels and they wouldn't turn unless I really forced them. turned on the car and it released some of the pressure but still is really hard to turn. its like the calipers wont let go of the brakes. but I know the calipers are good cuz I bought brand new ones, twice, I took them back thinking they were bad and they checked them and they were good. so I put them back on and tried what you said....but the wheels are still stuck.

 

i thought maybe brake lines and then replaced them. then i thought i bought a defective master cylinder. i took my car to my mechanic and that is where its at now. the mechanic is just charging me for the brake booster. he isn't charging me for labor. hes a good friend so im really hoping the brake booster is the problem. atleast i changed everything so my brakes will be good for a while.

 

Same procedure- then, without removing the brake lines, unbolt and separate the master cylinder from the brake booster. Check for wheel drag again.

Still dragging?

NO- Check the brake pedal position switch adjustment and pedal free play. If ok, adjust the booster pushrod clearance.

YES- Loosen the hydraulic lines at the master cylinder and check for wheel drag again.

Still dragging?

No- Replace the master cylinder

At this point I have to say that some are bad right out of the box but, I have to ask, did you bench bleed the master cylinder before installation?