W204 rear brakes

[Gfromleeds]

Evening gentlemen
About 3 months ago my break pad warning light came on !
I found the rear brake pads on the right side were very thin but the left side looked like new!
I replaced them anyway and all was well!
This afternoon on my mot I got an advisory for the same brake pads wearing thin again!
I've had a quick look and the caliper is releasing although when spinningi can hear the disc touching the pads at a certain point of rotation! (Discs were replaced at the same time as the pads)
Could a bad wheelbearing cause this?

 

[markjay]

Were the pads replaced by a garage (who presumably would have also checked the general condition of the calipers), or DIY (no disrespect)?

What is odd is that the car didn't fail its NOT, which it would have done if the 'surviving' pads weren't being used due to a fault with the braking system.

I think that you may have binding brakes on the side that wears thin... or possibly an issue with the ESP. Did the ABS/ESP light come up at all while driving? The ESP could incorrectly brake one wheel while cornering. Are both tyres the same make, and same wear? And are the tyre pressures correct?

I am not sure if a failed wheel bearing could cause this (unless, again, it confuses the EPS).

And the pads shouldn't be touching the discs when rotating the discs by hand..... is it the same on both sides?

 

[Gfromleeds]

Hi thanks the tires were bought as a matching pair about 6/7 months ago and both still look in great condition
I did the pad change, at the time I suspected a sticking caliper so checked and greased the slide pins and piston and everything seamed fine
I've only had the car since February so don't really know it's history could the hub itself be bent/ out of alignment? Could this cause the disc to "wobble" in relation to the caliper?
The mot said the service brakes are working both sides but the park brake on the right only just met requirements! I don't think this is related because the park brake uses shoes so that probably just wants adjusting. .

 

[markjay]

The parking brake does use drums and shoes at the rear... but if they're sticking on one side, it could (again) affect the ESP.

 

[190]

And the pads shouldn't be touching the discs when rotating the discs by hand..... is it the same on both sides?

No they shouldn't in a perfect world but most do touch very lightly unless the caliper pistons and guide pins are well lubricated. With only the hysteresis in the piston seals to withdraw the pads from the disk they have their work cut out especially with sliding calipers. I can get get the discs on the front dual piston calipers rotating freely by pulling back the dust seals and lubing the pistons with silicone brake grease but the rears are more of a challenge and it's harder to feel if they are rotating free because of the resistance from the diff.

I don't believe lightly touching pads have worn out in 3 months. The rear pads on my W204 lasted 73,000 miles. There is something else amiss. Does this car have the usually electronic stability control that can apply the brakes to one wheel only ?

 

[BlackC55]

I would say its a sticking calliper. Very common issue. Fitted 6 callipers this week for binding, seizing and uneven pad wear. Make sure the contact surfaces are immaculate and good high temp grease is used. NOT copper grease. Its not 1915.

An ESP issue is very unlikely.

 

[Petrol Pete]

Which high temp grease would you recommend Black55 ?

 

[geoffus]

Which high temp grease would you recommend Black55 ?

I’ve recently used this as it came with the rear discs I fitted to my A207.
Previously used copaslip for several years with no ill effects.

https://amzn.eu/d/a4asdlr

https://images.app.goo.gl/SbkYHksDddymQG4s7

 

[markjay]

I thought that genuine MB discs and pads come with a small satchel of brake paste?

Like this:

 

[BlackC55]

I’ve recently used this as it came with the rear discs I fitted to my A207.
Previously used copaslip for several years with no ill effects.

https://amzn.eu/d/a4asdlr

https://images.app.goo.gl/SbkYHksDddymQG4s7View attachment 164162

That stuff.

 

[BlackC55]

I thought that genuine MB discs and pads come with a small satchel of brake paste?

Like this:

Not anymore.

 

[ALFAitalia]

I thought that genuine MB discs and pads come with a small satchel of brake paste?

Like this:

Blimey!!!....you could get a lot of grease in one of those...

 

[W1ghty]

Not anymore.

Maybe a business opening for “Black55 Brake Disc High Temperature Grease”

 

[BlackC55]

Maybe a business opening for “Black55 Brake Disc High Temperature Grease”

I buy a bulk can of high temp grease. I've had it for ten years and never seems to go down.

 

[johnsco]

I bought MB Brake Paste 20 years ago from MB dealer
Brake pad paste pot A0019894751

As you say - It never appears to go down !