Brake Wear Sensors Needed?

cxc511 · 05-31-2012, 08:17 AM

I recently took my 2007 328i to the dealer after noticing a squeaking sound coming from my passenger rear brake (rolling at low speed and under light braking). Since I am still under CPO and MP until this September, I did not spend any time researching possible causes on my own. Turns out, I have a pretty well documented issue where the brake wear sensor which touches the rotor is the cause of the sound. The dealer is going to replace pads (and possibly rotors) on all four corners which is fine with me, but the existing pads still had a good amount of life on them.

What would happen if wear sensors were not installed with new brakes? I am happy to have my brakes replaced for free but I am just concerned this issue might occur again in the future when I would have to pick up the bill. To me, the benefits of the sensor don't seem worth it. However, I would not want a dash light or something similar that occurs when you run wheels without TPMS.

Any input is appreciated!

mid-corner fun · 05-31-2012, 10:01 AM

Quote:

Originally Posted by cxc511

I recently took my 2007 328i to the dealer after noticing a squeaking sound coming from my passenger rear brake (rolling at low speed and under light braking). Since I am still under CPO and MP until this September, I did not spend any time researching possible causes on my own. Turns out, I have a pretty well documented issue where the brake wear sensor which touches the rotor is the cause of the sound. The dealer is going to replace pads (and possibly rotors) on all four corners which is fine with me, but the existing pads still had a good amount of life on them.

What would happen if wear sensors were not installed with new brakes? I am happy to have my brakes replaced for free but I am just concerned this issue might occur again in the future when I would have to pick up the bill. To me, the benefits of the sensor don't seem worth it. However, I would not want a dash light or something similar that occurs when you run wheels without TPMS.

Any input is appreciated!

If the sensor is not installed it will display an error on the dash. Tuck the sensor away behind the wheel liner to avoid this and don't forget to check your brake pads once in a while.

Brad from the OC · 05-31-2012, 01:24 PM

Your sensor might have made contact with the rotor, when the sensor isn't secured properly to the caliper brake fluid bleeder valve protective cover. Someone who flushed your brake fluid might not have attached the sensor wire to the bleed valve dust cover allowing part of the sensor to come into contact with the rotor.

Efthreeoh · 06-01-2012, 06:11 AM

Quote:

Originally Posted by PeterM1

If the sensor is not installed it will display an error on the dash. Tuck the sensor away behind the wheel liner to avoid this and don't forget to check your brake pads once in a while.

+1. If you want to keep the sensor from making noise you can remove it from the pad and keep it connected. However, the car is expecting to see brake pad wear, so you may over time get the CBS out of whack and it start showing false indications of pad replacement. The system works using a 2-stage wear sensor. The CBS has an expected wear rate formula that is then augmented once the first stage of the wear sensor is reached. This data is used to estimate the remaining pad life, which is one of the menus in the CBS. The car is going to travel miles and not see any brake wear, so it might make the CBS think there is a problem with the system.

sonorous · 06-01-2012, 07:29 AM

I don't buy into the theory that this common "low speed rolling rear brake squeak" is related to brake sensors. It just does not sound right and after replacing my own brakes it does not really make sense technically to me. You should by all means accept new rear brakes from the dealer if they are offering that as a solution but I bet the sound will return quickly as others have reported. I personally believe in this theory and will be trying it myself in an upcoming weekend: http://www.e90post.com/forums/showthread.php?t=697365

cxc511 · 06-01-2012, 01:52 PM

Thanks for the replies. I'm headed back to the dealership on Monday, so I'll get more info on what exactly they say to be the problem and what will be replaced. At this point, I guess I'm happy to get the brakes freshened up for little or no cost before my CPO and MP expire. Based on the response about a dash light, I'll definitely want to have sensors intalled.

Sonorous, the only the I can say to support the dealer's diagnosis is that I read the wear sensors are installed on the passenger rear and driver front brakes, and I could tell my issue was coming from the passenger rear brake. The technician told me their was a service bulletin about this particular issue. It sounds like there are some work arounds with the sensors if this is in fact the root cause and I face the same problem again on my own dime.

Taipei-TT · 06-06-2012, 04:55 AM

Quote:

Originally Posted by sonorous

I don't buy into the theory that this common "low speed rolling rear brake squeak" is related to brake sensors. It just does not sound right and after replacing my own brakes it does not really make sense technically to me. You should by all means accept new rear brakes from the dealer if they are offering that as a solution but I bet the sound will return quickly as others have reported. I personally believe in this theory and will be trying it myself in an upcoming weekend: http://www.e90post.com/forums/showthread.php?t=697365

That link is a brilliant write up....but I still think it has something to do with the sensors as my car has a squeak but only on the right front. I've checked the pads, and they are both worn evenly with plenty of pad left. Both of the rotors look fine in all respects. Leaving only the sensor as an obvious potential culprit. Though, what I don't understand, is that the squeaking is very intermittent.

I had my pads ground so that the edge is not flat. On my Audis, this would eliminate squeaking completely as it allows the small metallic bits of brake dust to fall away instead of getting stuck between the pads and the rotor. On my BMW, this helped somewhat, but the problem still comes back and goes away on its own accord. More confusing, nothing looks glazed, and the coming and going of the problem seems independent of brake temperatures as I sometimes get squeaks on first brake application and sometimes after a nice/spirited bout of mountain driving where my brakes are HOT. The mysterious squeak!

05-31-2012, 08:17 AM	#1
cxc511 Private First Class 14 Rep 109 Posts Drives: 2007 E92 328 6MT Join Date: Jul 2010 Location: Erie, PA iTrader: (0)	Brake Wear Sensors Needed? I recently took my 2007 328i to the dealer after noticing a squeaking sound coming from my passenger rear brake (rolling at low speed and under light braking). Since I am still under CPO and MP until this September, I did not spend any time researching possible causes on my own. Turns out, I have a pretty well documented issue where the brake wear sensor which touches the rotor is the cause of the sound. The dealer is going to replace pads (and possibly rotors) on all four corners which is fine with me, but the existing pads still had a good amount of life on them. What would happen if wear sensors were not installed with new brakes? I am happy to have my brakes replaced for free but I am just concerned this issue might occur again in the future when I would have to pick up the bill. To me, the benefits of the sensor don't seem worth it. However, I would not want a dash light or something similar that occurs when you run wheels without TPMS. Any input is appreciated!
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05-31-2012, 01:24 PM	#3
Brad from the OC Private First Class 15 Rep 153 Posts Drives: 325Ia Alpine White Join Date: May 2006 Location: Southern California iTrader: (0)	Your sensor might have made contact with the rotor, when the sensor isn't secured properly to the caliper brake fluid bleeder valve protective cover. Someone who flushed your brake fluid might not have attached the sensor wire to the bleed valve dust cover allowing part of the sensor to come into contact with the rotor.
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06-01-2012, 07:29 AM	#5
sonorous Private First Class 14 Rep 124 Posts Drives: E90 335i Join Date: Mar 2007 Location: NY iTrader: (2)	I don't buy into the theory that this common "low speed rolling rear brake squeak" is related to brake sensors. It just does not sound right and after replacing my own brakes it does not really make sense technically to me. You should by all means accept new rear brakes from the dealer if they are offering that as a solution but I bet the sound will return quickly as others have reported. I personally believe in this theory and will be trying it myself in an upcoming weekend: http://www.e90post.com/forums/showthread.php?t=697365
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06-01-2012, 01:52 PM	#6
cxc511 Private First Class 14 Rep 109 Posts Drives: 2007 E92 328 6MT Join Date: Jul 2010 Location: Erie, PA iTrader: (0)	Thanks for the replies. I'm headed back to the dealership on Monday, so I'll get more info on what exactly they say to be the problem and what will be replaced. At this point, I guess I'm happy to get the brakes freshened up for little or no cost before my CPO and MP expire. Based on the response about a dash light, I'll definitely want to have sensors intalled. Sonorous, the only the I can say to support the dealer's diagnosis is that I read the wear sensors are installed on the passenger rear and driver front brakes, and I could tell my issue was coming from the passenger rear brake. The technician told me their was a service bulletin about this particular issue. It sounds like there are some work arounds with the sensors if this is in fact the root cause and I face the same problem again on my own dime.
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