Brake Sensors - BMW Forum

RyZak · 03-14-2005, 02:17 AM

Hey everyone,
this is my first post, followed just hours after my first mechanical work on my '93 525i. I had a relative show me the ropes. I just have a couple concerns that maybe you could help with. The first is regarding brake sensors. Namely, do I need to change them? I did my brakes after Midas showed my how worn the rotors and pads were. but my brake light had not yet come on. I simply reconnected them when I was finished with the job, and there is no brake light on. I realize that could mean they're fine and don't need replacing, or that they arent functioning properly and the light would not come on even if there was a problem (i've heard they are notorious for electrical issues). Any thoughts?

Second, my rear pads were a pain in the ass to get into the caliper. They just didn't fit...I could get one in but not the other. I eventually had to put the outside pad in, then bend the three "holding-prongs" (i don't know what they're called) down so I could squeeze the inner pad in, then I bent them back so I could pop it in to place. Common sense tells me this isn't normal. My brother-in-law (a car salesman) ordered the parts, and I trust he knows what hes doing, but I wonder if they were the wrong fit? Any thoughts?

Thanks folks,

RyZak
Oregon, USA
'93 525i Black/Black
114,000 miles

frank3 · 03-14-2005, 09:32 AM

Definetely replace brake wear sensors when you replace brake pads.

bryan1970 · 03-14-2005, 05:47 PM

yeah you should definatly replace the sensor when you put new pads on.

you say you had to bend the holding prongs???? are you talking about that stamped metal clip piece that is on the outborad side of the caliper?? becasue that is supposed to come off before you take anything apart. did you push the piston all the way back in the caliper when you tried to put the pads in?

The Deuce · 03-14-2005, 05:59 PM

That's normal that you would have to bend those a little to get them into the piston.

I had to do that with a couple of mine.

The wear sensors are $6 a piece or so. They really are meant to be single use and they may not last for this set of pads. I would get some and change them next time you rotate your tires, since that's as much as you have to remove to swap them out.

FWIW, if you are not getting a warning in the dash, they are working. You can verify this by unplugging one and turning the car to on. If one of the wires opens, you'll get the fault code. Ask me how I know this. :P

bryan1970 · 03-14-2005, 11:27 PM

oohhhh okay i know what clips your talking about now. i guess i kinda forgot about those on the inboard pad. did you use BMW pads or after market. becasue the BMW pads go in fairly easily. sometimes they can be a bit of a handful but for the most part they go in pretty easily. as long as the pad wasn't like really loose on the piston it should be okay.

CiscoKid · 03-15-2005, 09:29 AM

you dont nbeed to repace the sensors if the light doesnt go on.

if the light goes on, then you need to replace

RyZak · 03-16-2005, 01:51 PM

Thanks people,
thats helpful, and what i was hoping. I don't think he ordered BMW pads... think he realized I was trying to save $. The job was quoted at $500 by MIDAS, and I did it for $175. I'm feeling pretty good about that.
I actually bent the prongs back on the inner pad so that the fit perfectly into the piston. (and yeah, the piston was fully decompressed). I'll just have to order BMW parts if Im going to expect things to run smoothly.
Any good websites where i can order the sensors?
Thanks again,
Ryan

The Deuce · 03-16-2005, 03:33 PM

I think they are $6 or $12 a piece from the dealer, so I didn't look where they could be bought elsewhere.

probably bav auto woudl have them.

BMDubb · 03-17-2005, 10:25 AM

Quote:

Originally posted by The Deuce@Mar 16 2005, 03:33 PM
I think they are $6 or $12 a piece from the dealer, so I didn't look where they could be bought elsewhere.

probably bav auto woudl have them.

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Replace sensor if damaged:
Your "Brake Light" will illuminate when the sensor gets so many mm from the rotor, it does not have to actually touch the rotor to warn. Therefore if it never touches the rotor, it doesn't get damaged, it doesn't need replacing. If you damage it when replacing the pads, replace the sensor, otherwise just clean it with a brake cleaner and you should be okay.