... equipped with a hydraboost. That has been replaced but the issue still exists. After start up and driving the hydrolic lines build up pressure engaging all four sets of brake pads to the rotor. If I bleed the lines it will roll again until I use the brakes again. I can successfully bleed the lines behind each wheel AND at the master cylinder to free the brakes in their death-lock onto the rotors. I was about to replace the master cylinder and a mechanic friend said to wait on that and try replacing the power steering pump pressure switch. I currently don't have a lot of funds to be buying part after part so I'm trying to nail this problem with minimal cost, so any and all input will be greatly appreciated! I live in the general Phoenix, AZ area so my brake lines are not corroded or rusted (I have looked at all of them the best I could) and my Tahoe has a little over 200 k miles.

 

I have never seen all 3 (2 front & usually 1 rear) go bad at once,but the flexible (synthetic or rubber) brake lines can swell up and when they do they hold the pressure after applying the brakes.If it is the rear brakes then there is only one flex line to the differential to replace.The front wheels each have their own flexible line.I have had 3 of my older GM cars do this.

 

So you're thinking I need to replace the flex lines before I try replacing the master cylinder? Is there a way for me to tell if it IS the flexible lines that is causing this to happen??? Btw, thank you for responding to my post! And if anyone has some insight on this matter im all ears because I was prepared to go purchase a new master cylinder tomorrow morning since I finally drummed up enough money to buy one...

 

I would let the brakes lock up then unbolt the master cyl. from the hydro unit and see if they release. If they do then it's not the lines but the master or the hydro unit is not releasing. Should be able to move the master out some without cracking open the brake lines. Not normal for all 3 rubber hoses to fail at once.

 

One way to tell would be to crack the two lines(one line is front brakes and the other is rear) at the master cylinder after they are locked up.If that releases the pressure then the master cylinder is the problem.If the brakes are still locked up then the problem is the flex lines, as the pressure is trapped between the calipers and the flex lines.Are you positive all 4 brakes are locked up?A swolen rear flex line will lock both rear calipers.I have never had a master cylinder lock up all 4 brakes, but with these newer cars who knows.My older Malibu rear flex line swelled uo and was locking the rear brakes only.My 99 suburban L/F flex line swelled up at work and locked up.I had to change that line in the parking lot.

 

WoW! Yeah I'm pretty sure it's front and rear. Last time it happened I was in the median going south on 83rd Ave. I had to release pressure at the master cylinder and both ports had a decent amount of pressure built up in them when I cracked them loose. In the early stages of this I jacked the rear end up first to see if they were locked up and they were. Then I jacked the front up & founder the same thing... locked up. So this points to the master cylinder, huh?