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Discussion Starter #1
I know this is probably on here some where, but I tried searching, and am bad at it.

THe Cehck brake linings warning came up on my car yesterday.

I understand that there is a wearable sensor that has now worn to the point that it sets off the warning

Some questions:

How do I know which brakes need work, frnt to back, other than inspection?
I have to get a new sensor when I do the brakes correct?
Will installing the new sensor reset the warning?
How long will my pads last now that the light has come on?

I was hoping it would hold off until summer when I could get a BBK.

Thanks for any info.

Bob
 

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How do I know which brakes need work, frnt to back, other than inspection?
It is most likely the front, but short of inspection...i don't know how to check.

I have to get a new sensor when I do the brakes correct?
Yup. They're 20 bucks a pop and you only need 2 (one for the front, and one for the rear)

Will installing the new sensor reset the warning?
I'm pretty sure it will, but I'm not 100% sure. Maybe someone else can confirm this.

How long will my pads last now that the light has come on?
if it's the front, then you won't make it to summer. Not to mention that driving the M5 on worn pads is ill-advised. If it's the rear....then you may be able to squeeze by as long as you dont beat the hell out of them.
 

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...How do I know which brakes need work, frnt to back, other than inspection?
You don't
I have to get a new sensor when I do the brakes correct?
Correct
Will installing the new sensor reset the warning?
Yes
How long will my pads last now that the light has come on?
Depends on your driving. You should have a few thousand miles on them, but really it depends on it you are looking to re-use your rotors. More if no, less if yes, since you risk gouging the rotors.

d-
 

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Discussion Starter #7
Wow, thanks for all the help guys.

I might just get a set of pads for both ends along with new sensors to tide me over to the BBK.

This is the first car I've ever modified the chassis before the motor. I put KW V3's on, a dinan rear end and dinan sways. Next is probably the BBK, and it's still OK speed wise.

Such a great car.

Bob
 

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My warning light just came on 2 days ago. My mechanic felt them and said it's the fronts, rears have 25% left. He also said I should keep it to under 100 miles. The problem if I order some new rotors/pads, it won't come in for 7-10 days.

Is he exaggerating the 100 miles? If I'm going to replace the rotors anyway, is there damage to other parts of the car if I go a bit too long? I'm obviously not going to take it on the track or anything but I've got about a 40 mile RT commute. That'll be roughly 500 miles before the parts come in.
 

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I'm no mechanic, but I'd be stunned if BMW designed the brake warning light to come on 100 miles before they needed to be changed.

I'd guess closer to 1000.

d-
 

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Doug is right, however, the pads could be worn more on one side than the other. And, the sensor only works on the left front inside, IIRC. So if any of the other 3 pads are worn too much, your indi could be correct.
 

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...So if any of the other 3 pads are worn too much, your indi could be correct.
There is another sensor in the right rear so that would make it 2 that you don't know.
 

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There is another sensor in the right rear so that would make it 2 that you don't know.
Except that there are 4 pads on an axle - 1 inner & 1 outer per wheel. And the sensor is only on 1, which means there are three pads (as indicated by jclyman) you don't know about on the axle that says it is worn. There are 4 other pads (1 measured, 3 not) on the other axle.

Of course, unless you have a sticking caliper or pad, all 4 should be worn equally...

Sorry M5CCIE-son, the master (Jclyman) remains the master...

d-
 

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By the way, my 1997 318ti had VERY UNEVEN pad wear on the left rear ... fixed now, but it wore out a rotor without any warning light.

As Doug suggests, it is unlikely for a sticking pad or caliper to be a problem on our cars, but not out of the question. In fact, I do remember a post on that very same issue (ruined rotor and no warning light) about 6 months ago.
 

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Except that there are 4 pads on an axle - 1 inner & 1 outer per wheel. And the sensor is only on 1, which means there are three pads (as indicated by jclyman) you don't know about on the axle that says it is worn. There are 4 other pads (1 measured, 3 not) on the other axle.

Of course, unless you have a sticking caliper or pad, all 4 should be worn equally...

Sorry M5CCIE-son, the master (Jclyman) remains the master...

d-
Lol, but in that case it would be 6. :cheers:
 

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There may be 6 "UNmeasured" pads on an E39 M5, but there are a total of 8 pads (stock) on our cars ... last time I looked ... (with the sensors on the inner pads of the left-front and the right-rear) ... That means that any one of 6 pads may be completely worn down to the rotors, if there were any sticking pistons or calipers (it is almost always the pistons that stick, rarely the pads or calipers). The warning light is just a "heads-up" telling you to check ALL your pads. A broken or raw wire to the sensor could also cause the warning.

It isn't that tough to check ... I would, if I got a warning.

:M5launch:
 

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There are places that offer free brake checks. I had mine checked at Midas for free. They seemed pretty honest and tried to save me a few bucks for the sensor, but from my understanding, once you trip the sensor, you pretty much need a new one.
 

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I just had my front brakes replaced -- the sensor never triggered. I was down to metal on metal on the RIGHT front inner pad before I realized I needed brakes. The shop said this is common. New pads, rotors, sensor=$900.
 

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Discussion Starter #18
Well I just put new pads and sensors on all around (they were all just about to metal)

Problem - Slight squeak just before stopping and the stupid 'Check Brake Linings' refuse to go off.

Ideas?

Bob
 

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Well I just put new pads and sensors on all around (they were all just about to metal)

Problem - Slight squeak just before stopping and the stupid 'Check Brake Linings' refuse to go off.

Ideas?

Bob
Ignition Key to position 1 for 30 seconds to reset the memory that holds the warning light...

d-
 

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Discussion Starter #20
I'll give that a shot.

Thanks!
 
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