Brianwilson1990

Ok. I have had a continuing problem with the front brakes locking on my 2007 Denali yukon. I have changed the pads, rotors, had the rotors turned, changed the rubber lines to the calipers, changed the master cylinder, unplugged the abs pump, changed both front calipers. Vacuum then pressure bleed system, took to gm dealer for a flush. Vhanged both front wheel hubs and sensors were included. My headers are nowhere near my brake lines so I know it isn't heat issue. Nothing seems to work.
on a long trip (doesn't seem to matter how much I use the brakes) of about 20minutes one of my front brakes will start to lock up. Sometimes it's the left sometimes the right. Sometimes both brakes. But never the rear. If I let my car idle in the driveway for about 30 minutes I get in the car and the brake pedal is hard as a rock. I Crack both front bleeder and I get only fluid with lots of pressure. What could possibly be causing this?

dsmmace

Do you have a cam and is your truck turbocharged or supercharged?

Brianwilson1990

I do have a cam. But this problem started before the cam swap.

dsmmace

I'm wondering if the check valve on the brake booster has a problem causing inconsistent vacumn.

Brianwilson1990

It's cheap enough. I just bought and installed a new one. Hope this fixes it but any other ideas?

Brianwilson1990

Brake booster check valve didn't help at all. Also cleaned my abs/wheel speed sensors front aND back. Didn't help. Any ideas guys?

firebladeJJ

iTrader: (1)

Try blocking off the vacuum to the booster and see if it still does it. it be like driving around with manual brakes. it will be a bear to stop but if they dont lock up like they have been, then its booster vacuum related. just sounds like something is bleeding into the system and pushing the master brake cylinder down or out, however you wanna look at.