Pad wear indicator AWOL

[Monkey Wrench]

Hey there,
Sun "was" out so started on cleaning rusty bits from the rotors. Glad I started this, found other concerns, including no wear sensor on the left front of my 2007 R230 !?, Right hand has one.
Not gonna lose sleep but....am I missing it or is this MB train of thought? Can't see any cable connection....

 

[Blobcat]

Hey there,
Sun "was" out so started on cleaning rusty bits from the rotors. Glad I started this, found other concerns, including no wear sensor on the left front of my 2007 R230 !?, Right hand has one.
Not gonna lose sleep but....am I missing it or is this MB train of thought? Can't see any cable connection....

“Normally” just one on the front and one on the rear or opposite callipers

 

[Monkey Wrench]

“Normally” just one on the front and one on the rear or opposite callipers

Thank you.
Suppose the idea is to have them regularly checked. The replacement Mintex MDB2064 slot straight in, pad suits other MB's

 

[DREAMER NO2]

Just two in some cases , with one on each of the front wheels, left and right .

 

[Monkey Wrench]

Just two in some cases , with one on each of the front wheels, left and right .

Ok, checked, this is my case,

 

[Snake Charmer]

My S211 has two sensors per axle set at different pad depths.

 

[Monkey Wrench]

My S211 has two sensors per axle set at different pad depths.

View attachment 83591

View attachment 83592

maybe you get a pre warning...?
mine look like the black version.....and its right next to the backplate so "CHANGE NOW !" kinda warning....

 

[Monkey Wrench]

Picking up where I left off on Sunday via thread "What have you done to your Merc today", I thought I'd continue my "brakes" interest here.
Before today, I had recently replaced rear pads but then they were sticking, and I mean proper sticking, very hot after a mile or three.
Through a bit of chit chat, the suspision was, likely corroded pistons/caliper, jamming in the almost fully retracted position, frankly they probably havn't sat this retracted for some years, certainly not in my ownership.
This afternoon I celebrate with 400mls of San Miguel Especial, having beat mother natures wrath of fine weather, and replaced the pistons, seals and dust covers (£32), but.... witness zero corrosion, on anything.




This is a bit of a curve ball for me, always found corrosion with binding calipers.
Picture this, bare caliper, no seal, original piston, starts in ok but sticks halfway, can only go further with mechanical assistance. Compared to, same bare caliper, new piston glides in beautifully. Can move without hinderance.
Using my trusty Oxford Precision vernier caliper. I measure original piston, lighter in weight, maybe aluminum but dark in colour, 41.98mm to 42.00mm diametre, over its length. New one, weighty steel thats either polished or chromed (can't quite tell) measures 41.92mm to 41.98mm....
The size is the only thing I see, as the trouble in this case, I aint never seen before. Missed the opportunity to measure the caliper bore (weather was pending)
Can material swell? Thinking about it, the portion that doesnt want to glide in has not been in contact with brake fluid for years....this is getting scientific.
Anyway, 3 mile test drive sucessful, ice cold calipers upon return.
Oh and new rotors to compliment the pads.
Next stop front rotors (summertime).

During this task I found that a pump like to pressurised the caliper upon pedal movement, good job the catch tray was in place.....

 

[Snake Charmer]

@Uncle Benz will be along shortly to explain about plastic pistons. What did you clean the caliper with? Looks a very uniform finish.

maybe you get a pre warning...?
mine look like the black version.....and its right next to the backplate so "CHANGE NOW !" kinda warning....

Yes, they bring the warning up at different wear limits. Threw me a curve ball as I was looking into 330mm discs and calipers as replacements and stupidly assumed the wear sensor would give me a warning as to when I needed to buy everything in. Turns out both sensors had worn through and been dealt with by the previous owners local garage. I had to fit standard discs and pads to stay on the road.

 

[Uncle Benz]

Yeah, pistons are made of plastic. They mushroom a bit with age. Does exactly what you found. You’ll be good now you’ve replaced them. Not many people seem to be aware of this problem

 

[Monkey Wrench]

@Uncle Benz will be along shortly to explain about plastic pistons. What did you clean the caliper with? Looks a very uniform finish.

Yes, they bring the warning up at different wear limits. Threw me a curve ball as I was looking into 330mm discs and calipers as replacements and stupidly assumed the wear sensor would give me a warning as to when I needed to buy everything in. Turns out both sensors had worn through and been dealt with by the previous owners local garage. I had to fit standard discs and pads to stay on the road.

I didnt actually use any cleaner, just wiped out with a microfibre cloth, I was encouraged how clean they were.
With your discs sorted its good to know youll get that pre warn now.

 

[Monkey Wrench]

Yeah, pistons are made of plastic. They mushroom a bit with age. Does exactly what you found. You’ll be good now you’ve replaced them. Not many people seem to be aware of this problem

Wow, every day's a school day, that is brave..... I thought SL stood for Super Light, but thats taking things a little too far.... On closer inspection I'm now thinking Bakolite type material....
My research suggests this caliper is standard on many Mercs, must be loads of unknowing customers having calipers replaced because of this

Thank you

 

[EmilysDad]

Wow, every day's a school day, that is brave..... I thought SL stood for Super Light, but thats taking things a little too far.... On closer inspection I'm now thinking Bakolite type material....
My research suggests this caliper is standard on many Mercs, must be loads of unknowing customers having calipers replaced because of this

Thank you

Perhaps there are stainless pistons available for you car?