Ok experts i need brake help. List of new parts include: Pads, rotors, brake booster(x2), brake master cylinder, newer abs hydraulic unit, all 4 speed sensors. All needed replaced. Had an initial problem with sloppy brake pedal, replaced booster, it squealed, exchanged it, everything was fine. So i thought. Rears werent engaging, even after being bled. Didnt realize until front brakes locked up, 4x4 light, abs light, brake light illuminated. Replaced abs unit, in doing so, stripped the master cylinder, so used 82k abs unit and new master cylinder, bled, brakes felt better than ever. For 2 weeks, now front brakes lock up again. Replaced wheel speed sensors, as that fixed someone elses problem. Not mine. Work fine at first start up, but after a few local miles, fronts lock up again. Crack both lines on the master cylinder, front brakes release after cracking the top line, im guessing goes to driver side. So im thinking, brake lines are fine because i got fluid from the master, if they were collapsing under heat, thered be no return fluid to the master. Calipers should be fine because if they were sticking theyd either be stuck, or not stuck. So, leaves me with a bad booster, again? What are your thoughts. This is driving me crazy.
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More checking and trying to diagnose tonight as i drove it 6 total miles and no more warning lights, but the fronts are still sticking. Get home, i have some brake pedal travel. Pull the check valve, can hear the pop as pressure is released from the power booster, brake pedal is hard as a rock, no travel. Hook the check valve back into the booster, turn the car on, i have a little brake pedal travel. Im on a flat surface, so car on, it should roll in gear, so put it in reverse, it doesnt move. Slightly crack open top line on master cylinder, car starts rolling backwards. Im thinking if the booster was bad enough to lock up the brakes, wouldnt that mean the rod would be pushed into the master where it wouldnt release, meaning the brake pedal should be on the floor??
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Crack the rubber brake hoses at the calipers, the rubber hoses are probably bad
I bought lines yesterday, and guess dont have the right tools to get the lines off, because the wont seperate from the hard line, and i stripped the driver side. I at first thought lines were ok because i was getting fluid returned at the master, dont know why i thought that. But got new ones and a new booster ordered just in case, and ill try lines again with line out wrenches and see what happens. Thanks for the reply.
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E53 brake lines is a big job to do correctly, especially the rears which require the rear axle carrier to be dropped. Unfortunately rusted leaking lines are common.
i suspect whoever replaced the booster didn't get the push rod lined up correctly and broke the master cylinder but it's just a guess
good luck!
There's a valve in your ABS system that closes and shuts off your rear brakes if it senses air in the lines. It does this as a safety feature, in case a rear line breaks and you're losing fluid, it shuts off your rear brakes at the ABS module so you can at least maintain front brakes until you reach a repair shop. They only did this for a few years on the E53's before they realized how much this negatively affected owners that were either DIY'ers or took it to local repair shops for simple brake repairs. Because, well you guessed it, the BMW dealer is the only place you can take it to get the valve opened back up to properly bleed the brakes for full function. Don't feel bad, it happened to me and continues to be one of those things people learn AFTER they've already opened up there rear brake lines and introduced air into the system to lock the valve shut.
05 BMW X5 - 09 Yamaha R6 - 04 Ski-Doo mxzX 440 lc race sled - 04 Ford F350 SCrew PSD
Its the fronts that lock up. I replaced the front brake lines today at lunch, drove it 2 miles and they locked up, 4x4, brakes, and abs lights came on, might have been a stored code. I released the pressure, cleared tge code and drove it back to the shop. After I work went and drove to see if i could do some testing do6r brake booster, 45 miles no problems. Gonna drive it to work on the morning and see what happens.
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