Mercedes-Benz Forum banner

Brake Pad wear indicator - km left

31K views 93 replies 16 participants last post by  DEVOURS 
#1 ·
Hi all.

wouldn't you know it. We are having wet slushy snow here near Toronto and my brake indicator is flashing on/off. With 60k km on the odometer that seems reasonable enough. Problem is I have a trip planed this weekend and won't be able to put new pads in before then. Anyone have a guess-estimate for how long I have before I'll hear metal on metal?:eek:
 
#2 ·
Hey, guenter. If your trip is mostly highway you should be absolutely fine. There is usually a decent amount of material once you get the alert, if you did mostly stop and go city driving it might be only a few hundred miles, but for mostly highway you'd probably have 1,500, 2,000 or maybe even more miles. (I'm sure you can do the conversion to km in your head better than I can...)

Have a great trip!

Take care and enjoy the ride,
Greg
 
#3 ·
Greg, perfect! Thanks for that :thumbsup: .... it'll make this trip a lot more enjoyable if I don't have to be constantly on the alert...
 
#5 ·
The bad news is that the dealer will probably want to change the rotors at the same time.....so as long as you DIY you should be OK for a bit.
 
#6 ·
guenter

Not sure of the setting in the B but other cars I have owned gave an indication at about 10 - 15 % left. So you should have a few Kilometres left for a short trip but get them replace before the pad damages the rotor.

I guess that you already checked but is the brake fluid level OK ? Usually the level will drop as the pads wear and need replenishing prior to a brake job.

Bill
 
#7 ·
How many kms you got on odometer?

No the dealer will not change the rotors unless they are badly pitted have good thickness they will just do the brakes like on my car ones.

I was told when the light starts flashing you have from 2000-5000kms to go.
depends on where you drive
 
#8 · (Edited)
well, I've finally had a look at my brake pads.
Interestingly the dealer only had an indicator in one pad, the one which was low and all others were maybe half worn. Interesting I thought, had I gone in for a dealer service I'm positive all pads would have been replaced. Ergo, Dealers don't necessarily do a proper job on their own vehicles ;) I replaced the one brake pad about 1000 km after the light came on... I probably easily had another 1000 km left on it.
I tried to reuse the indicator, as I always do a few times, but it couldn't be done this time. Turns out the pads are electrically conductive and once the insulation on the indicator pin is worn, the light comes on. So, don't wast your time trying to reuse :thumbsup:
the actual re and re was easy and straight forward, the most difficult and time consuming part was taking the wheels off.
 
#10 · (Edited)
Bill,

I'm sure there is only 1 brake sensor in the front, as per my pics on the brakes a while back.
Maybe the rears have one also,....I'm not sure. I'll check!

DEVOURS

ps: Guenter, You only replaced one pad,...???
Could you give us more details as to what was changed on the 2 front wheels please.
 
#11 · (Edited)
To answer some of the questions
The rear pads had no holes for the sensors. Makes sense since they only get changed for every three or four front pads.... there is a pretty good view of all the outside pads as well without taking wheels off. Moreover, I did notice that the inside pads were consistently a 'bit' more worn than the inside ones. All the front pads had holes for the sensors but interestingly only one of the pads - the one that was worn, outside passenger side - had a sensor in it. A shop could make a bit of money doing that :D although I can't believe the dealer having done that on purpose.
So of course, cheap as I am, I only changed the one pad but now will have to monitor them periodically. Will buy a new sensor and put it into the pad most worn. Eventually I'll get it to even out - unless of course for some reason there is differential wear.... I doubt that though.
Sure the pads come for fronts and rears seperately in sets of four. Note though that the paste was NOT included (it WAS for my 300E pads that I bought just a few weeks ago. Moreover, the B200 front pads cost me cdn $110 while the 300E front pads with past cost only $75. Also interesting was that these new B200 pads, unlike those that were installed, had an 'extreme' bevell on the sides.... never seen that before. Presumably they'll never squeel.
 
#12 ·
Thanks guenter,

I wasn't sure when you said you were only changing one pad.
I would think that that's not recommended. Breaking in the pads on both sides evenly should give you straighter and safer stopping.

I've never heard of changing only one pad, ever!!
 
#13 ·
DEVOURS I would have agreed with you before coming across this particular situation. The car was a dealer loaner when I bought it with 20k km on the odometer and clearly taken care of by the dealership. It is clear that they did not replace the pads in sets. Instead they replaced as needed. I guess there could have been an early problem that I'm unaware of that caused uneven wear. The inside pad on the passenger side was only 1/2 worn while the outside pad was 90% worn.... brakes did not pull etc and braking was perfectly fine. Having now only replaced the one pad, I must say that the brakes again work just fine, do not pull and there is no indication of any asymmetry whatsoever in braking performance.... could it be that replacing pads in pairs is old thinking along the lines of changing oil every 5k km?
 
#14 ·
Cheap disc calipers like the B 200s (that have mono piston sliding calipers rather than double or quad piston fixed calipers) always wear the inside pads (the ones in contact with the piston) way faster than the outer ones. It's inherent in the design, but it gets worse if the sliding surfaces are seized or sticking.

The other issue with M-B and smart pads is delamination due to rust. So even if the pad has some good life left in it, the friction material might be in the process of detaching from the backing plate. So economising by retaining a relatively unworn outer pad may be false economy in the end, with a scored disc as a souvenir.

That price for B 200 pads is asinine, I will have to get mine from Germany!
 
#15 ·
The problem with changing one pad is that the friction material could possibly be of of a different make up / composition which could lead to better or worse braking on one side.

If you were adamant on not changing the full set of 4 pads (strongly recommended) the minimum you ought to change is the pad & its mirror image on the other side ie change both left & right outers (or inners) in this way you will not get uneven braking on one side. But as DEVOURS states ideally all 4 pads should be changed.

Regarding sensors if you wanted them on the other front pads you would obviously have to add extra wiring to the other side of the car, hardly worth the hassle imho. The sensor warning is only a guide and should not replace visual inspection or regular servicing.
 
#16 ·
Hi guys, just replaced the front pads on our 180B as the wear indicator started flashing up the other day. I carefully refitted the indicator sensor into the new pad but the warning still keeps flashing up.
As the sensor had part of the plastic/rubber coating worn away (due to contact with the disc) will it still be making contact through the pad and flashing the warning on?
I guess I will have to get a new sensor but in the mean time would removing the sensor and unplugging it from the connector block on the caliper stop the warning from flashing up until I can get a new sensor fitted?

Cheers.
Chris
 
#17 ·
Hi bruno999slade & welcome to the forum. Where are you located ??

Have you definitely refitted the sensor back in the correct position??

Not sure if these sensors work by a disconnection of the circuit (ie where he contact with the rotor wears away the circuit in the sensor and thus triggers an alarm) or if the alarm is triggered by the sensor earthing on the rotor. I would presume the former and an easy way of checking would be to as, you say, just disconnect the sensor unit but in this case your alarm would be on all the time.

If the alarm is not flashing when you remove the sensor wiring then you could temporarily insulate the worn away part of the sensor with heatproof paint.

But I do suspect that it will be the first option & you will need to replace the sensor.

Perhaps a member who has actually replaced his pads after the sensor light can (excuse the pun) throw some light on this.
 
#18 ·
Hi kdbcom, thanks for your reply. I'm up in York and have had this 180B for nearly a year now. It's got about 27k on it now so we've done about 11k over the past 11 months.
I took great care in refitting the sensor back in the new pad exactly as it came out of the old one. I took care as I had a Zafira before this car and broke the sensor on that car. The "Brake pad check" warning still appeared so I got a new sensor and fitted that but it always came up with "Brake pad check" every time we started up. Even with the sensor removed. I presumed it was logged in the memory and needed the dealer to clear the fault code but I begrudge paying through the nose for a dealer just to plug a laptop in and click a few buttons.
I'll try this one with the sensor disonnected and get a new one anyway but I am worried I will have to call on the dealer to reset it in the end.
I assumed the warning is triggered on the B class by the disc rubbing through the insulation of the sensor and earthing but as there are two wires going to the sensor so perhaps the two ends melt together or are allowed to connect somehow when the disc wears through to them. I hoped being surrounded by nice new pad material they would be OK but obviously not.

Chris
 
#19 ·
Chris in that case I think that the sensor is as I mentioned earlier and the circuit breaks when the sensor contacts the disk. There are methods of resetting the fault codes which the members may be able to tell you how to do. If it is not too much hassle at the moment leave it till you get a reply.

You may get a quicker response by starting a new thread "how do you reset fault codes"

Keith
 
#20 ·
It looks that our "B"'s have one weak point - brake pads. That squeaky and rusty noise is really annoying, especially after rain or car wash. I'm thinking of going to get it serviced and replaced. The car is less than 2 years old and should be covered under Wear and Tear warranty. Odo is 20,500 km. Other option would be getting replaced with some good and harder brakes.

Speaking of indicators, from my experience with other cars, it is not unusual to have them installed in only one brake pad as a factory standard. Even for Mercedes.
 
#21 · (Edited)
I doubt whether your M/B dealer would be able to supply a harder pad, you would need to use another manufacturers product such as these :- Performance Brakes | Products | Green Stuff

Green stuff or for really hard road use Red stuff.

This site apart from giving reference number by model also gives the opportunity to see the exact shape of the pad with dimensions.

bruno999slade they quote the following regarding wear indicators which would tend to suggest that you will need to change your pad sensor

Quote On BMW and Mercedes models the pad has a wear receptor on the top of the backplate and the wear lead clips into this. It is not necessary to replace this wire at every pad change unless the contactor has activated and is worn.

It would appear from your post that your sensor has activated
 
#25 ·
Can you tell from the circuit diagram DEVOURS whether, as appears to be confirmed by EBC in my post above, the sensor works by a breaking of the circuit (due to the sensor rubbing on the disk) if that is the case there is a good chance that just replacing the sensor with a new one will complete the circuit and stop the fault alarm coming on. There will of course be a record of this left in the computers fault log but this would presumably get cleared the next time the car goes in and should cause no other problems.
 
#29 ·
Keith,

I haven't pulled up that schematic yet but logic tells me that it's a NO(normally open) circuit.

The brake pad wears until the 2 contacts(2 wires on the sensor) make contact with the metal rotor, and only then is the circuit closed and completing the loop and a signal sent to the computer and the warning on the dash appears. That's my guess anyway.

D
 
#26 ·
I think that when guenter finished changing out the pads with the new sensor the alarm was reset.

With most manufactures disconnecting the battery for 30 seconds and reconnecting it will clear most faults. Mercedes probably has a back up battery to keep everything in memory just to have you come to them.:nono: Big Brother, Mercedes and Santa Claus all keep an eye on you.

Wife's last car would continue showing a fault ( after it had been remedied ) for a week or so. Dealer recommended disconnecting the battery to clear, as that was the way they did it. Gas cap not tight was the cause and friend with a Subaru was told same thing.

Bill
 
#27 ·
With most manufactures disconnecting the battery for 30 seconds and reconnecting it will clear most faults. Mercedes probably has a back up battery to keep everything in memory just to have you come to them.:nono: Big Brother, Mercedes and Santa Claus all keep an eye on you.

Bill
Hey Bill, this seams to work cause I had a problem with emergency flasher stuck and the road service tech disconnected to battery to clear the problem.

it's worth trying, just remember that you will loose all liter/km history on your OBC

D
 
#30 · (Edited)
Thanks for that reminder Daniel!! 👍

I sure don't want to lose all the good #'s I have on my OBC. :read:


D :eclipsee_steering:


ps: Photoshop can only help so much. ;) :yelrotflmao:
With your good numbers you probably check them before you go to bed:D:D and have them posted on the night stand:thumbsup:

All things are possible with Photoshop, the rogue's gallery might take more training however. And a much more powerful computer.:smashpc: to compile the massive changes needed.

Do not expect these reading ever

Bill

created lovingly with photoshop
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top