E38 Check brake linings/brake light message
RCG52
message and brake light is still on. Do they have to be reset this or will
they automatically go off when the condition is fixed?
Kyle and Lori Greene
"RCG52" <rudyge...@comcast.net> wrote in message
news:0ridnWca8d5...@comcast.com...
Did you replace the sensor or forget to plug it back in when you replaced
the pads? There's one on the front driver's side (left) and one on the rear
right.
Kyle.
98 740iL
97 M3
Jeff Strickland
In simple terms, the sensor looks much like a fuse. As the brake pads wear,
the sensor comes in contact with the rotors and breaks, a new sensor has to
be installed to repair the break.
"RCG52" <rudyge...@comcast.net> wrote in message
news:0ridnWca8d5...@comcast.com...
RCG52
"Jeff Strickland" <spamc...@yahoo.net> wrote in message
news:z5edne6ajc7...@ez2.net...
RCG52
backside off while removing it. So when replaced, it will turn off the
check message and brake light?
"Kyle and Lori Greene" <kylog...@tampabay1.rr1.com> wrote in message
news:feOQd.87620$qB6....@tornado.tampabay.rr.com...
tech27
(or vis versa). Always replace the sensor(s) when you do a pad change, one
or both depending on which set you replace.
"RCG52" <rudyge...@comcast.net> wrote in message
news:atedndFLf5_...@comcast.com...
Jeff Strickland
band of metal that goes across the face (side towards the rotor). Yours will
not have the metal band, or if you got to it early enough you might see it
broken.
As the pads wear down, the band touches the rotor and this turns the light
on. The band eventually breaks. If you get into the habit of looking at the
brake pads while washing your car, you can usually see if the pads are
nearing end-life. If you manage to replace the pads before the warning light
comes on then you can avoid buying new sensors.
The warning light does not differentiate between front and rear brakes, so
there could be two sensors broken or the sensor you look at first is not the
broken one. The sensors are on diagonal tires, front left and right rear if
I remember right.
"RCG52" <rudyge...@comcast.net> wrote in message
news:AN2dnV2qVbP...@comcast.com...
Dave Plowman (News)
RCG52 <rudyge...@comcast.net> wrote:
> I did not replace the sensor with a new one and I chipped a piece of the
> backside off while removing it. So when replaced, it will turn off the
> check message and brake light?
If it's like the E39, just replacing the sensors won't turn off the
warning immediately. You have to turn on the ignition without starting the
engine for a couple of minutes. Or it will just happen after a few days
normal driving.
--
*I don't suffer from insanity; I enjoy every minute of it.
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
Dave Plowman (News)
Jeff Strickland <spamc...@yahoo.net> wrote:
> If you manage to replace the pads before the warning light
> comes on then you can avoid buying new sensors.
You might. However, the plastic becomes very brittle with the heat, and it
may just break up on removal - even if unworn. Don't ask how I know. ;-)
--
*Generally speaking, you aren't learning much if your lips are moving.*
Bill K. Sydney AU
> If you look at the part closely, you will find that there is a very thin
> band of metal that goes across the face (side towards the rotor). Yours
will
> not have the metal band, or if you got to it early enough you might see it
> broken.
>
> As the pads wear down, the band touches the rotor and this turns the light
> on. The band eventually breaks. If you get into the habit of looking at
the
> brake pads while washing your car, you can usually see if the pads are
> nearing end-life. If you manage to replace the pads before the warning
light
> comes on then you can avoid buying new sensors.
>
However, if you are one who religiously checks the break pads whenever you
wash your wheels, then you can get a lot more distance on the pads before
replacing them - especially on the lightly stressed rear brakes.
My wife put nearly 30,000 km on her E36 from the time the rear brake sensor
turned the check brake disks light on, until I had to replace the pads and
sensor to get the car through the annual registration inspection. Still a
safe amount of pad left before hitting metal when I replaced them.
The front sensor went on my E34 shortly before the annual inspection was
due, so I pulled the sensor, clipped the wire and twisted both wires
together to close the circuit. It took a day or two before the ECU turned
the dash light off. With no warning lights alight the car passed the
inspection. About six-months later I decided to replace the pads and sensor
in preparation for a holiday trip. Once again, still a safe amount of pad
left.
But if you don't visually keep a check on your pads regularly, by all menas,
get the dealer to whack in new brakes as soon as practical after the light
goes on. For the DIY guys like me, a new brake sensor costs about $5 for the
E34 and $14 for the E36. And where I live the front sensor is in the
passenger side brake, the back in the drivers side rear brake pad. Same brak
e pad as anywhere else, but we put the driver's seat on the right hand side
of the gear shifter.
Bill K.
tech27
> band of metal that goes across the face (side towards the rotor). Yours
> will
> not have the metal band, or if you got to it early enough you might see it
> broken.
As the pads wear down, the band touches the rotor and this turns the light
Not exactly. The sensor is a normally closed circuit. The sensor is a U
shaped band which completes the circuit. As the pads wear the band gets worn
down. When it wears enough to wear off the "bottom" of the U, the circuit
becomes open and triggers the warning light. This normally closed
configuration is why you will get the warning if any part of the circuit
becomes open due to a loose or broken wire anywhere in the circuit.
The band eventually breaks. If you get into the habit of looking at the
brake pads while washing your car, you can usually see if the pads are
nearing end-life. If you manage to replace the pads before the warning light
comes on then you can avoid buying new sensors.
I would recommend new sensors with every pad change (to avoid having to
troubleshoot the circuit when the pads seem to have life left), but you are
correct.
Cheers
Jeff Strickland
"tech27" <tec...@mail.anonymizer.com> wrote in message
news:RETQd.44593$NC6....@newsread1.mlpsca01.us.to.verio.net...
I have driven over 100,000 miles in four years, and have never replaced the
Brake Wear Sensors. I manage to get to my brakes before the warning comes
on, and I have re-used the old sensors twice on the front, and once on the
back. So, I know the sensor does not need to be replaced if the warning is
not on.
Jeff Strickland
> There are, in fact, 2 sensors driver front brakes and passenger rear
> brakes (or vis versa). Always replace the sensor(s) when you do a pad
> change, one or both depending on which set you replace.
>
That's false. If the warning is not on, there is no need to replace the
sensor.
The sensors are mounted on the left front and right rear. Whether this is
the driver side or not depends on the market the car was built for.
tech27
"Jeff Strickland" <cr...@yahoo.com> wrote in message
news:g9mdnbI_UuY...@ez2.net...
> > I have driven over 100,000 miles in four years, and have never replaced
> > the
> Brake Wear Sensors. I manage to get to my brakes before the warning comes
> on, and I have re-used the old sensors twice on the front, and once on the
> back. So, I know the sensor does not need to be replaced if the warning is
> not on.
Makes sense. But is it common t to get 33,000 and 50,000 miles on front/rear
brakes? Good for you if you do.
Cheers
tech27
>
> "tech27" <tec...@mail.anonymizer.com> wrote in message
> news:obPQd.44563$NC6....@newsread1.mlpsca01.us.to.verio.net...
>> There are, in fact, 2 sensors driver front brakes and passenger rear
>> brakes (or vis versa). Always replace the sensor(s) when you do a pad
>> change, one or both depending on which set you replace.
> That's false.
Well, that's what I was told and always did. The cost of a sensor isn't that
much, so I always had it done.
If the warning is not on, there is no need to replace the
> sensor.
Yes, but mine always were, so I never really had the option.
>
> The sensors are mounted on the left front and right rear. Whether this is
> the driver side or not depends on the market the car was built for.
My fault. I not used to thinking of RHD vehicles.
The Malt Hound
Easily that, and much more. Drive only on the open highway and don't
make a lot of panic stops.
For most of us who drive in more varied consitions than that we may
not do quite so well.
-Fred W
Jeff Strickland
I don't know if it's common or not, but my commute lets me drive for nearly
an hour without using the brakes at all. So, I am not surprised that I get
50k from my front brakes.
Dave Plowman (News)
Jeff Strickland <spamc...@yahoo.net> wrote:
> I don't know if it's common or not, but my commute lets me drive for
> nearly an hour without using the brakes at all. So, I am not surprised
> that I get 50k from my front brakes.
You drive straight out of your garage onto a deserted road?
Sounds like heaven. Can I buy next door to you? ;-)
--
*Xerox and Wurlitzer will merge to market reproductive organs.
The Malt Hound
"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:4d3ed4a...@davenoise.co.uk...
> In article <Kuqdnc8UOvH...@ez2.net>,
> Jeff Strickland <spamc...@yahoo.net> wrote:
>> I don't know if it's common or not, but my commute lets me drive
>> for
>> nearly an hour without using the brakes at all. So, I am not
>> surprised
>> that I get 50k from my front brakes.
>
> You drive straight out of your garage onto a deserted road?
> Sounds like heaven. Can I buy next door to you? ;-)
'tis the 'merican highway system, Dave. Lots of open road...
-Fred W
Jeff Strickland
>
> "Jeff Strickland" <cr...@yahoo.com> wrote in message
> news:4J-dnT0ZmoS...@ez2.net...
>>
>> "tech27" <tec...@mail.anonymizer.com> wrote in message
>> news:obPQd.44563$NC6....@newsread1.mlpsca01.us.to.verio.net...
>>> There are, in fact, 2 sensors driver front brakes and passenger rear
>>> brakes (or vis versa). Always replace the sensor(s) when you do a pad
>>> change, one or both depending on which set you replace.
>
>
>> That's false.
>
> Well, that's what I was told and always did. The cost of a sensor isn't
> that much, so I always had it done.
>
> If the warning is not on, there is no need to replace the
>> sensor.
>
> Yes, but mine always were, so I never really had the option.
So, the truism is that IF the light is on the sensor(s) must be replaced.
There is no need to replace the sensor(s) if the light is not on, despite
any advice to the contrary.
tech27
> So, the truism is that IF the light is on the sensor(s) must be replaced.
> There is no need to replace the sensor(s) if the light is not on, despite
> any advice to the contrary.
Half correct. Systems like this are designed to fail on the side of caution,
therefore if the light is not on there is no need to replace, BUT, if it IS
on it could be the sensor OR the circuit or both (or you might need to put
factory air in the rear driver tire - you know how funny some cars are -
-; ).
Jeff Strickland
Come on! If the light is on, the sensor has touched the rotor and the odds
favor that it will be worn through by the time one gets the brakes apart.
Factory air in the rear tire??? What in Hell does that mean?
tech27
Factory air was just a joke. (-; (-;
Seriously though, to make sure you understand how it works, it's NOT the
sensor touching the rotor that triggers the warning (the circuit is normally
CLOSED), but rather that the sensor HAS touched the rotor AND been worn
through so that the "loop" is broken. That's what triggers the warning. And
unless there is a break in the circuit elsewhere, when the sensor triggers
the warning it absolutely must be replaced. No options ever.
Cheers
Dave Plowman (News)
tech27 <tec...@mail.anonymizer.com> wrote:
> Seriously though, to make sure you understand how it works, it's NOT the
> sensor touching the rotor that triggers the warning (the circuit is
> normally CLOSED), but rather that the sensor HAS touched the rotor AND
> been worn through so that the "loop" is broken.
No - the loop doesn't have to be broken. The loop is there simply to
indicate the system is correctly installed - ie without the loop the
warning light would stay on, as if a sensor had been omitted. But shorting
a sensor to ground also brings on the light without breaking the loop.
> That's what triggers
> the warning. And unless there is a break in the circuit elsewhere, when
> the sensor triggers the warning it absolutely must be replaced. No
> options ever.
I'd say a sensor which had triggered the circuit - but wasn't worn through
so the loop had gone OC might just still work after the pad was replaced.
But in my experience they break up when removing from the pad anyway, so
it's academic.
--
*How do you tell when you run out of invisible ink? *
The Malt Hound
> In article <045Sd.45856$NC6...@newsread1.mlpsca01.us.to.verio.net>,
> tech27 <tec...@mail.anonymizer.com> wrote:
>> Seriously though, to make sure you understand how it works, it's
>> NOT the
>> sensor touching the rotor that triggers the warning (the circuit is
>> normally CLOSED), but rather that the sensor HAS touched the rotor
>> AND
>> been worn through so that the "loop" is broken.
>
> No - the loop doesn't have to be broken. The loop is there simply to
> indicate the system is correctly installed - ie without the loop the
> warning light would stay on, as if a sensor had been omitted. But
> shorting
> a sensor to ground also brings on the light without breaking the
> loop.
Sorry, Dave. That's just wrong.
I dug through the schematics and the circuit starts at the Instrument
cluster (Connector A pin 19) and goes through the front left brake pad
sensor and then through the right rear brake pad sensor, eventually to
ground. Either sensor touching one of the brake disks (assumed to be
grounded also) would not set off the sensor, in fact it may delay the
onset of the alarm. It would have to cause a break in continuity to
set it off.
-Fred W
tech27
>> through
> so the loop had gone OC might just still work after the pad was replaced.
> But in my experience they break up when removing from the pad anyway, so
> it's academic.
Okay, I might be inclined to accept that a short to ground will also trigger
the light as another fallback, possibly as a result of another parameter
which causes the light to go on if the resistance comes close to or is a
short. This would be a good backup to the system so that it would not show
all is good because the circuit is completed to ground. HOWEVER - everything
I've read and seen has indicated that it is the wearing down of the loop
until the cross portion is worn away that causes the OC which triggers the
light.
Cheers
The Malt Hound
...and you would be correct in your inclination.
-Fred W
Jeff Strickland
>
> "Jeff Strickland" <cr...@yahoo.com> wrote in message
> news:WaidnXtKJtA...@ez2.net...
>>
>> "tech27" <tec...@mail.anonymizer.com> wrote in message
>> news:5NNRd.45523$NC6....@newsread1.mlpsca01.us.to.verio.net...
>>>
>>> "Jeff Strickland" <cr...@yahoo.com> wrote in message
>>> news:iIadnennhZ6...@ez2.net...
>>>> So, the truism is that IF the light is on the sensor(s) must be
>>>> replaced. There is no need to replace the sensor(s) if the light is not
>>>> on, despite any advice to the contrary.
>>>
>>> Half correct. Systems like this are designed to fail on the side of
>>> caution, therefore if the light is not on there is no need to replace,
>>> BUT, if it IS on it could be the sensor OR the circuit or both (or you
>>> might need to put factory air in the rear driver tire - you know how
>>> funny some cars are - -; ).
>>
>> Come on! If the light is on, the sensor has touched the rotor and the
>> odds favor that it will be worn through by the time one gets the brakes
>> apart.
>>
>> Factory air in the rear tire??? What in Hell does that mean?
>>
> Having a bad day, Jeffrey?
> Factory air was just a joke. (-; (-;
>
> Seriously though, to make sure you understand how it works, it's NOT the
> sensor touching the rotor that triggers the warning (the circuit is
> normally CLOSED), but rather that the sensor HAS touched the rotor AND
> been worn through so that the "loop" is broken. That's what triggers the
> warning. And unless there is a break in the circuit elsewhere, when the
> sensor triggers the warning it absolutely must be replaced. No options
> ever.
>
I completely agree, if the light is on the brakes must be serviced.
My point was that the brakes can be serviced without replacing the sensor if
the service is performed before the light comes on. In my case, I have
replaced the front brakes twice and the front rotors once in 100,000 miles,
and I have not replced the sensor yet because I noticed the brakes were
approaching end life before the light came on.
You said the sensor must be replaced each time the brakes are serviced, my
point was that this is not necessary IF the brakes are serviced before the
light comes on.
Dave Plowman (News)
The Malt Hound <Malt_Hound@*no spam please*yahoo.com> wrote:
> > No - the loop doesn't have to be broken. The loop is there simply to
> > indicate the system is correctly installed - ie without the loop the
> > warning light would stay on, as if a sensor had been omitted. But
> > shorting
> > a sensor to ground also brings on the light without breaking the
> > loop.
> Sorry, Dave. That's just wrong.
> I dug through the schematics and the circuit starts at the Instrument
> cluster (Connector A pin 19) and goes through the front left brake pad
> sensor and then through the right rear brake pad sensor, eventually to
> ground. Either sensor touching one of the brake disks (assumed to be
> grounded also) would not set off the sensor, in fact it may delay the
> onset of the alarm. It would have to cause a break in continuity to
> set it off.
Well, I've had a sensor that looked as if the loop was still made, but the
plastic cover had been ground off and it had obviously been touching.
But I didn't check the sensor for continuity, so I'll take your word for
it. I concluded it worked this way because that's how I would have
designed it ;-) Because it would also show up *any* fault in the
wiring.
--
*Seen it all, done it all, can't remember most of it.
tech27
>
> Well, I've had a sensor that looked as if the loop was still made, but the
> plastic cover had been ground off and it had obviously been touching.
> But I didn't check the sensor for continuity, so I'll take your word for
> it. I concluded it worked this way because that's how I would have
> designed it ;-) Because it would also show up *any* fault in the
> wiring.
>
> --
> *Seen it all, done it all, can't remember most of it.
>
> Dave Plowman da...@davenoise.co.uk London SW
> To e-mail, change noise into sound.
He's right Dave. You can assume that *MOST* circuits in a car are normally
open and are activated when closed (or grounded to complete the circuit). By
making the wear sensors normally open, ANY BREAK IN THE CIRCUIT, whether it
be the loop worn through, or any part of the wiring breaking, the warning
comes on. It's just the safest way to monitor ALL the system. Used to be a
nightmare when American manufacturers used relays, which the turned on a
idiot light (bulb). If the bulb was burned out (unlikely but possible), the
system would relay the fault but the light wouldn't go on so you knew
nothing. You were "supposed" to check that all the lights worked when
starting the engine and observing that they all lit up.
tech27
"The Malt Hound" <Malt_Hound@*no spam please*yahoo.com> wrote in message
news:4LadnRJRF4t...@adelphia.com...
Just being polite. Didn't want to infuriate Dave. (-;
The Malt Hound
>
> He's right Dave. You can assume that *MOST* circuits in a car are
> normally open and are activated when closed (or grounded to complete
> the circuit). By making the wear sensors normally open, ANY BREAK IN
> THE CIRCUIT, whether it be the loop worn through, or any part of the
> wiring breaking, the warning comes on. It's just the safest way to
> monitor ALL the system. Used to be a nightmare when American
> manufacturers used relays, which the turned on a idiot light (bulb).
> If the bulb was burned out (unlikely but possible), the system would
> relay the fault but the light wouldn't go on so you knew nothing.
> You were "supposed" to check that all the lights worked when
> starting the engine and observing that they all lit up.
>
It actually would not be that hard to design the circuit to do both,
ie detect both an open and a short to ground, by floating the circuit
at some predetermined voltage/resistance above ground. Then the
circuit could detect either condition. This would allow the earlier
detection tha the metal filament has contacted the metal brake disk.
But then you'd have to worry about the sensor getting wet and the
metallic brake dust forming a short, etc.
I'm betting the BMW engineers simply decided to ensure the the
tolerances were such that the sensor would contact and break early
enough (as does seem to be the case) that there is reasonable surety
that all the pads are nearly shot.
-Fred W
Dave Plowman (News)
> Just being polite. Didn't want to infuriate Dave. (-;
Not possible. ;-)
--
*On the seventh day He brewed beer *
Dave Plowman da...@davenoise.co.uk London SW
Dave Plowman (News)
> ie detect both an open and a short to ground, by floating the circuit
> at some predetermined voltage/resistance above ground. Then the
> circuit could detect either condition. This would allow the earlier
> detection tha the metal filament has contacted the metal brake disk.
> But then you'd have to worry about the sensor getting wet and the
> metallic brake dust forming a short, etc.
I must have a closer look, but I thought a sensor was totally enclosed in
plastic until it 'wears'?
> I'm betting the BMW engineers simply decided to ensure the the
> tolerances were such that the sensor would contact and break early
> enough (as does seem to be the case) that there is reasonable surety
> that all the pads are nearly shot.
Funnily, I recently had the nasty grinding noise we used to have before
warning systems on my E39 - as one pad had hit the metal. But not the one
with the sensor. UK designed cars seem to have the sensor on the other
side from BMW - which of course is basically LHD. Luckily, it was the
second set of front pads on those discs so they were due for changing
anyway. But the pistons and slides on both callipers appeared exactly the
same, so I ruled out any seizure.
--
*Women who seek to be equal to men lack ambition.
Dave Plowman (News)
tech27 <tec...@mail.anonymizer.com> wrote:
> He's right Dave. You can assume that *MOST* circuits in a car are
> normally open and are activated when closed (or grounded to complete
> the circuit). By making the wear sensors normally open, ANY BREAK IN
> THE CIRCUIT, whether it be the loop worn through, or any part of the
> wiring breaking, the warning comes on.
Not really so today. I'd make it so any imbalance in the circuit - either
short or open circuit, on either leg - triggered a latch that lit the
warning. Standard practice in decent domestic burglar alarms.
> It's just the safest way to monitor ALL the system. Used to be a
> nightmare when American manufacturers used relays, which the turned on a
> idiot light (bulb). If the bulb was burned out (unlikely but possible),
> the system would relay the fault but the light wouldn't go on so you
> knew nothing. You were "supposed" to check that all the lights worked
> when starting the engine and observing that they all lit up.
Well, a signal lamp like this - even a tungsten one - should have a very
long life, since it's rarely on. Or just use an LED.
Just debating a point. ;-)
--
*Everyone has a photographic memory. Some don't have film *
tech27
> Not really so today. I'd make it so any imbalance in the circuit - either
> short or open circuit, on either leg - triggered a latch that lit the
> warning. Standard practice in decent domestic burglar alarms.
Yes, but the really good ones also montor fluctuations in the resistance of
the contacts. That way it would also detect a wire being placed across the
sensor to defeat it.
> Well, a signal lamp like this - even a tungsten one - should have a very
> long life, since it's rarely on. Or just use an LED.
An LED would be fine, but the liability of not getting a critical message
due to a burned out or fawlty (Basil!), bulb would not be acceptable.
tech27
> In article <ToySd.46274$NC6....@newsread1.mlpsca01.us.to.verio.net>,
> tech27 <tec...@mail.anonymizer.com> wrote:
>> > ...and you would be correct in your inclination.
>
>> Just being polite. Didn't want to infuriate Dave. (-;
>
> Not possible. ;-)
Is that a challenge, you malodourous pervert? I fart in your general
direction. Reply once more and I shall taunt you again, you snivelling
English person!
The Malt Hound
>
> "Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
> news:4d41612...@davenoise.co.uk...
>> In article
>> <ToySd.46274$NC6....@newsread1.mlpsca01.us.to.verio.net>,
>> tech27 <tec...@mail.anonymizer.com> wrote:
>>> > ...and you would be correct in your inclination.
>>
>>> Just being polite. Didn't want to infuriate Dave. (-;
>>
>> Not possible. ;-)
>
> Is that a challenge, you malodourous pervert? I fart in your general
> direction. Reply once more and I shall taunt you again, you
> snivelling English person!
Ooops. I took Dave's reply to mean that it was not possible to
*avoid* infuriating him.
;-)
-Fred W
Dave Plowman (News)
tech27 <tec...@mail.anonymizer.com> wrote:
> >> Just being polite. Didn't want to infuriate Dave. (-;
> >
> > Not possible. ;-)
> Is that a challenge, you malodourous pervert? I fart in your general
> direction. Reply once more and I shall taunt you again, you snivelling
> English person!
6 out of 10. I've been insulted by experts in my time. ;-)
--
*I got a sweater for Christmas. I really wanted a screamer or a moaner*