W211 brake disc overheating

[Henkka]

My right rear brake disc started overheating a while ago. It started making a sound while braking, and I went to put my hand on it. It was very hot. I’ve done a few test runs with the car, about 7km without braking. The disc was still hot. Now the left side has started doing the same, though it is not as hot as the right side.
What could be the problem? The pads are ok.

 

[EmilysDad]

could be as simple as the pads sticking in the caliper but more likely the pistons inside the calipers sticking. Either new calipers or rebuild them with new pistons & seals.

 

[Wighty]

My right rear brake disc started overheating a while ago. It started making a sound while braking, and I went to put my hand on it. It was very hot. I’ve done a few test runs with the car, about 7km without braking. The disc was still hot. Now the left side has started doing the same, though it is not as hot as the right side.
What could be the problem? The pads are ok.

One of the specialists on here @Uncle Benz was saying recently that the rear brake calliper pistons on the W211 are plastic and can swell with age and heat .

 

[mersum1es]

yeah, pistons go 'mushroom' shape and not moving freely. This is noticed especially after pad change, this is especially problem of SBC brake system (don't know did they change something when SBC was discontinued). OP is not specifying what age W211 it is, signature shows only W124...

 

[Henkka]

yeah, pistons go 'mushroom' shape and not moving freely. This is noticed especially after pad change, this is especially problem of SBC brake system (don't know did they change something when SBC was discontinued). OP is not specifying what age W211 it is, signature shows only W124...

Sorry for that. Year 2003. So is my whole SBC system due for a replacement?

 

[Henkka]

could be as simple as the pads sticking in the caliper but more likely the pistons inside the calipers sticking. Either new calipers or rebuild them with new pistons & seals.

Would be quite a coincidence for both sides to go inside such a short time.

 

[M80]

Would be quite a coincidence for both sides to go inside such a short time.

Not really, they're the same age / mileage.

Chock the fronts, jack each corner, neutral no parking brake, see how each wheel rotates. Freely or not?

 

[Henkka]

Not really, they're the same age / mileage.

Chock the fronts, jack each corner, neutral no parking brake, see how each wheel rotates. Freely or not?

Not freely. Takes a little force to turn it. Especially without the tire, I need two hands to rotate it.

 

[M80]

Not freely. Takes a little force to turn it. Especially without the tire, I need two hands to rotate it.

It, or both?
Anyway there is binding.
That's the caliper or the parking brake.
Most likely the caliper, but prising the pads a little would prove that.
Removal of the caliper to see if the pads are tight would be next.

 

[Henkka]

It, or both?
Anyway there is binding.
That's the caliper or the parking brake.
Most likely the caliper, but prising the pads a little would prove that.
Removal of the caliper to see if the pads are tight would be next.

I just last night realized the left side also heating up, so I haven’t tried that side. Right side I know is difficult to spin, as I’ve lifted the car up to see what’s wrong.
Caliper is so tightly in place that I can’t open the two bolts holding it together. I tried that.
I did put a screwdriver in between the pad and the disc, and tried lifting a little. It’s unclear if it moved out of place, or if I was able to lift the piston. Something was moving, though it required quite an amount of force to make it move.

 

[Uncle Benz]

Sorry for that. Year 2003. So is my whole SBC system due for a replacement?

No need for that. It’s most likely to be a problem with the caliper pistons. When were the pads last replaced? It’s usually shortly after new pads that this rears its head

 

[Henkka]

No need for that. It’s most likely to be a problem with the caliper pistons. When were the pads last replaced? It’s usually shortly after new pads that this rears its head

30 000km ago or so.

 

[Uncle Benz]

Be aware that the SBC system should be disabled before fiddling with the brakes. It can switch on unexpectedly and cause injury. You can unplug the unit under the bonnet and put a cloth between. You’ll need to snip a cable tie to achieve this.

 

[EmilysDad]

..... It’s usually shortly after new pads that this rears its head

That's exactly the case when Emily had problems with her car's brake caliper ..... EmilysDad had just changed the pads.

 

[Wighty]

That's exactly the case when Emily had problems with her car's brake caliper ..... EmilysDad had just changed the pads.

Talking about yourself in the third person has got to be a sign of madness (says Wighty )

 

[Snake Charmer]

Be aware that the SBC system should be disabled before fiddling with the brakes. It can switch on unexpectedly and cause injury. You can unplug the unit under the bonnet and put a cloth between. You’ll need to snip a cable tie to achieve this.

SBC
It can't be bargained or reasoned with, doesn't feel pity, remorse or fear and it absolutely will not stop.

 

[mioba]

Talking about yourself in the third person has got to be a sign of madness (says Wighty )

I think he is trying to hide the fact that the third person caused a problem

 

[EmilysDad]

I think he is trying to hide the fact that the third person caused a problem

like who? lol

 

[Larkone]

Talking about yourself in the third person has got to be a sign of madness (says Wighty )

I asked myself the question and they don't agree with that diagnosis