Help me troubleshoot my brakes

[Iforgetalot]

99 540i manual.

Pulling the out of the driveway early this week I immediately noticed that the brakes/parking brake were stuck. The car would move with some resistance and as soon as I let off the gas you could feel the car was slightly braking. Put it in reverse, rolled back and hit the brakes, pulled and release the parking brake lever but no luck. Drove it to the end of the street slowly to see if it would loosen up, again, no luck so I drove it back home and parked it, brake smoke now visible. I was 90% convinced it was a stuck parking brake.

Yesterday I went to work on it. The first problem I encountered was that I could not get the drivers side rear caliper off. The rotors have worn out so much that they now have a slight lip/edge that was catching the pad when sliding the caliper off the disk (thanks PO for replacing brakes and leaving worn out disk, good job!). The caliper, however did not compress, as much as I tried it didn't budge. This kept me from being able to remove the caliper because the pad was catching on the rotors edge. Got up this morning open the caliper bleeder nut an I was able to compress the caliper bare handed and I was greeted by caliper happy ending. Caliper is off the rotor at this point.

For troubleshooting's sake I then closed the bleeder nut, removed the brake reservoir cap, and tried to compress the caliper but it didn't move. I then opened the bleeder and was able to compress it by hand. Caliper seems to bee good it just wont compress with the bleeder closed.

So, am I correct in thinking that I may have one or more of the following. Clogged line, bad MC, ABS something or other? So as not to go around in circles what would you guys recommend as the most efficient way to attack this.

Parking brake cable and shoes seem to be in good shape and may just need some lubrication.

[BimmrMeUpSnotty]

When a caliper starts to grab out of the blue, usually is one of three things, bad dry rotted brake lines, condensation of water built up in the lines, or blown caliper seals. Check the dust boots, if there is a tear, there will be rust on the piston, rebuild the calipers. I’d go ahead and do them anyway, the brake lines, give them a good look, dry rot will introduce air into the system, replace them anyway, bleed the brake system, sounds like the po neglected the car, and shame on you for just driving it without having gone through the car yourself.

[Cobra1956]

You should be able to move the pad off the rotor with a screw driver. Use the rotor as the fulcrum .

[Iforgetalot]

You should be able to move the pad off the rotor with a screw driver. Use the rotor as the fulcrum .

Correct, I should. I tried prying, pulling, banging, mild cursing, heavy cursing, more prying, c-clamp, on and on... it did not move, not even a hair! If it would have moved I would not be posting about this here. I was able to compress the caliper only after releasing pressure by loosening the bleeder screw. Had to stop working on it for now but next step is to pump the brakes wit the bleeder screw open to make sure its not clogged and then troubleshoot my way to the MC.

[Cobra1956]

Well assuming you are going to pop for new rotors, grind the lip off and get the calipers off and you can begin to trouble shoot. Do you have a proper caliper compressor in the event you get the rotors off?

[Cobra1956]

My guess would be that the pistons had crap on them from the brakes be run down and even more so if the rotors are thin. Pistons should probably been pulled and that stuff cleaned off but maybe it just got pushed back and the o ring is holding that thing up and or jammed due to debris

[Iforgetalot]

Just bought new rotors, lines, and pads. Also ordered the caliper rebuild kit. Will check for clogged lines prior to any install.

[crazy4trains]

You can buy rebuilt calipers for cheap. Saves you the time and hassle of doing a rebuild. Most likely you'll get a set of ATE calipers that are just like the calipers that were put on the car at the factory.

[Iforgetalot]

You can buy rebuilt calipers for cheap. Saves you the time and hassle of doing a rebuild. Most likely you'll get a set of ATE calipers that are just like the calipers that were put on the car at the factory.

Nahh. Rebuilt calipers $50.00+. DIY new seal kit ~$20.00 for both. Easy DIY.

[Cobra1956]

LOL remember that when you are doing it and be careful not to damage the piston on the way out. If you have not done this before some wood blocks or shims help. Best of luck finding the issue.

[BimmrMeUpSnotty]

A rag to catch the piston and just a tad of compressed air, makes a great BANG!!! To me, hardest part is the dustboot. Petroleum jelly is your best friend for this job.

[crazy4trains]

Nahh. Rebuilt calipers $50.00+. DIY new seal kit ~$20.00 for both. Easy DIY.

For me, time is money. If I can spend a little more money and save a bunch of time I will do it.

[Cobra1956]

If you have not done this before the key is the relationship between the piston and the square cut o ring as that's what makes all calipers work. Clean those pistons well. You can use brake fluid, caliper grease for lube.

[Iforgetalot]

*UPDATE*

So I replaced rotors, pads, shoes, pad wear sensor, ABS sensor, Hydraulic hose, rebuilt both rear calipers with new boot and seal and adjusted the e-brake, bled the system; Done! I started the car put it in gear and , NOPE! no go, the brakes are locked. At tat point the next few days flashed before my eyes. What I saw was a lot of web search, troubleshooting, $pending. etc. I read a post that mentioned something about angle sensors, ABS sensors, ABS module and how to step by step troubleshoot.

First thing I did was turn the wheel all the way to both sides then brought it back to center. I read on line this may reset steering column angle sensors which in turn may have something to do with the locked rear brake condition. I then pressed the brake pedal and this time I heard a click and the pedal traveled like it should and the brakes are no longer locked. I have to admit this was kind of a parts shotgun blast approach but it needed all the brake hardware anyways. I hope I don't have some kind of brake issue lurking about just waiting for the worst moment. I think I'm good for now. Thanks to all that replied and helped.

[Cobra1956]

Good news that you got it solved. ABS sensors are just magnet that can be cleaned and rarely fail. Another little pointer for later reference with electronics, work with a lot of cars. Disconnect the battery and short the positive and negative cables together for a few minutes. Resets a ton of issues on the electronics and the dealers do this also. No power, I use my jumper cable to do this.