Intermittent brake failure

in2wishn · 07-08-2022, 03:52 AM

So as a preface to this: I've contacted 3 separate shops local to the LA area that specialize in BMW's, as well as doing as much research online on this issue as possible.
I drive a 2012 E92 328i 77k odo, and have had 2 separate instances of my brakes failing within my 1 month of ownership.
Prior to owning this, I had a 2009 E90 328i 146k odo that I owned for 6 years, and aside from swapping out rotors, pads and sensors, never had any issues.
Upon buying the car; I had inspected the car thoroughly myself and done an OBDII scan on it, only finding a code for the ABS sensor; for which I didn't pay much mind to at the time. 2 weeks after buying it, the brakes wouldn't engage until I slammed on them HARD coming to a complete stop at a red light. I rolled halfway into the intersection, and am incredibly fortunate that no cars were in front of me or driving into the street at that time given it was a busy street midday. After this scare, I immediately replaced the rotors, sensors and pads, having thought that my troubles were gone as my mechanic told me that my rotors needed to be replaced anyway as they were very worn down, this was last week. Today, I was in a shopping plaza and a similar thing happened to me, where I was rolling with my foot off the accelerator and when I braked it kept rolling until I SLAMMED on the brakes. I was immediately petrified and called up the guys who helped install my brakes recently, having taken it to the shop and had them drive the car around to get a feel for it, they returned confused because the car didn't have any codes and ran great. This is the same way it was the last time it happened too; no codes and the issue was a 1 off thing (at the time). They suggested I contact another shop that deals with BMW's specifically and are performance oriented as they may have more information on the issue. Having spoken with one of the guys there they mentioned that because my brake fluid hadn't been swapped in the past 2 years it might be that.. or the vacuum pump, but either way it would have to be taken to the shop and dropped off to be properly diagnosed.. but they wouldn't have availability for the next 2 weeks. Feeling relieved that my issue could probably be remedied with a simple brake fluid flush I went on to swap out my ignition coils and plugs, filter and a few other maintenance repairs I needed to do. Unable to shake the severity of what could happen, I looked over my carfax records for the car, and to my fortune (unfortunately) the previous owner would exclusively have the car worked on at BMW dealerships.. and he'd gotten a brake fluid flush in February of this year, 2,000 miles ago. At this point, having exhausted most of the possibilities that could've attributed to this brake failure, I am assuming it's likely either A. a failed vacuum pump, B. master cylinder, or C. ABS failure.

I'm just a nursing student though who's a hobbiest; by no stretch of the imagination am I a professional mechanic so I really have no clue what to do here. Being that this issue could happen at random, and involves the most crucial element to my safety when driving I need to address this issue as soon as humanly possible.

Has anyone experienced anything similar?
To any technicians or specialists, given the circumstances and information; what comes to mind as to being the possible culprit?

Any and all help/guidance would be GREATLY appreciated.

Brian86 · 07-08-2022, 10:16 AM

Do these cars have a pressure regulator for the brake boost vacuum?

Intermittent leak on the vacuum line?

Just throwing spaghetti at the wall here...

in2wishn · 07-12-2022, 12:31 AM

I'm not exactly sure. At this point we setup an appointment at century west bmw to have one of their techs diagnose the car properly.. wishing for the best

335i54n · 07-12-2022, 12:51 AM

something like this maybe (but still attached), broken vacuum supply to the booster. not common to e90 but sometime hard plastic line split at the end. also not hard to setup a mechanical vacuum gauge to monitor that line vacuum, since its a safety issue till u resolve it

https://www.e90post.com/forums/showthread.php?t=1937681

07-08-2022, 03:52 AM	#1
in2wishn New Member 2 Rep 9 Posts Drives: BMW 328i 2012 Join Date: Jun 2022 Location: Los Angeles, CA iTrader: (0)	Intermittent brake failure So as a preface to this: I've contacted 3 separate shops local to the LA area that specialize in BMW's, as well as doing as much research online on this issue as possible. I drive a 2012 E92 328i 77k odo, and have had 2 separate instances of my brakes failing within my 1 month of ownership. Prior to owning this, I had a 2009 E90 328i 146k odo that I owned for 6 years, and aside from swapping out rotors, pads and sensors, never had any issues. Upon buying the car; I had inspected the car thoroughly myself and done an OBDII scan on it, only finding a code for the ABS sensor; for which I didn't pay much mind to at the time. 2 weeks after buying it, the brakes wouldn't engage until I slammed on them HARD coming to a complete stop at a red light. I rolled halfway into the intersection, and am incredibly fortunate that no cars were in front of me or driving into the street at that time given it was a busy street midday. After this scare, I immediately replaced the rotors, sensors and pads, having thought that my troubles were gone as my mechanic told me that my rotors needed to be replaced anyway as they were very worn down, this was last week. Today, I was in a shopping plaza and a similar thing happened to me, where I was rolling with my foot off the accelerator and when I braked it kept rolling until I SLAMMED on the brakes. I was immediately petrified and called up the guys who helped install my brakes recently, having taken it to the shop and had them drive the car around to get a feel for it, they returned confused because the car didn't have any codes and ran great. This is the same way it was the last time it happened too; no codes and the issue was a 1 off thing (at the time). They suggested I contact another shop that deals with BMW's specifically and are performance oriented as they may have more information on the issue. Having spoken with one of the guys there they mentioned that because my brake fluid hadn't been swapped in the past 2 years it might be that.. or the vacuum pump, but either way it would have to be taken to the shop and dropped off to be properly diagnosed.. but they wouldn't have availability for the next 2 weeks. Feeling relieved that my issue could probably be remedied with a simple brake fluid flush I went on to swap out my ignition coils and plugs, filter and a few other maintenance repairs I needed to do. Unable to shake the severity of what could happen, I looked over my carfax records for the car, and to my fortune (unfortunately) the previous owner would exclusively have the car worked on at BMW dealerships.. and he'd gotten a brake fluid flush in February of this year, 2,000 miles ago. At this point, having exhausted most of the possibilities that could've attributed to this brake failure, I am assuming it's likely either A. a failed vacuum pump, B. master cylinder, or C. ABS failure. I'm just a nursing student though who's a hobbiest; by no stretch of the imagination am I a professional mechanic so I really have no clue what to do here. Being that this issue could happen at random, and involves the most crucial element to my safety when driving I need to address this issue as soon as humanly possible. Has anyone experienced anything similar? To any technicians or specialists, given the circumstances and information; what comes to mind as to being the possible culprit? Any and all help/guidance would be GREATLY appreciated.
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07-08-2022, 10:16 AM	#2
Brian86 Captain 638 Rep 766 Posts Drives: e36 M3, e91 325xi, N50 Xterra Join Date: Dec 2020 Location: Pittsburgh iTrader: (0)	Do these cars have a pressure regulator for the brake boost vacuum? Intermittent leak on the vacuum line? Just throwing spaghetti at the wall here... __________________ Sometimes a bolt is just a bolt.
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07-12-2022, 12:31 AM	#3
in2wishn New Member 2 Rep 9 Posts Drives: BMW 328i 2012 Join Date: Jun 2022 Location: Los Angeles, CA iTrader: (0)	I'm not exactly sure. At this point we setup an appointment at century west bmw to have one of their techs diagnose the car properly.. wishing for the best
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07-12-2022, 12:51 AM	#4
335i54n Lieutenant 295 Rep 525 Posts Drives: e90 335i, e39 m5 Join Date: Nov 2020 Location: socal iTrader: (0)	something like this maybe (but still attached), broken vacuum supply to the booster. not common to e90 but sometime hard plastic line split at the end. also not hard to setup a mechanical vacuum gauge to monitor that line vacuum, since its a safety issue till u resolve it https://www.e90post.com/forums/showthread.php?t=1937681 Last edited by 335i54n; 07-12-2022 at 12:59 AM..
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