W211 2006 e320 resetting brakes - no gap between front pads and discs

SA1

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Hi,
I have recently replaced all the brakes disc and pads and front wheel bearings, but after reactivating the SBC (used iCarSoft - confirmed all pressure sensors were reading around 70bar), I found that on driving the car a few meters it became obvious that the front pads were stuck on the discs. I previously checked that the calipers moved Ok when I had deactivated the SBC, and the wheels spun, but did notice there was very little clearance between the discs and the pads. I had also bled the brakes with a pressure bleeder. The back ones bled ok, but the front driver side required more pressure as I had a bit of air in the caliper, but then it was Ok and got a firm brake pedal after removal of the air. The passenger front side did not bleed properly when I released the bleed screw - this was also the side where I had very little clearance between the pad and the disc. I have ordered a new bleed screw in case it was blocked but I am suspicious that the problem might be related to this, but not sure - no air in this side though, as I did not remove the caliper like I did for the drivers side front (hence the air which got in). I checked both wheel sensors as I got C2452 error RHS speed sensor - 'inspect distance from rotor to sensor'. Both gave 9 Mega Ohms when tested on car (wiring clip to sensor).
As I have been at this job for a while and I am not quite sure of my next step (plus it would be great to finish this job!), any comments back would be appreciated!
 

DREAMER NO2

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Where did the parts come from, are they genuine Mercedes purchased with the vin number .
Could be that the disc or pads are to thick. Also on some cars the backs calipers or discs are not made by the same maker as the fronts / like ATE on the front and Girling in some cases on the rear .And also the brake fluid fill tank is split in to 2 on some syestems and only the front section gets filled up , in this case only the front caliper will bleed . If the rear part of the fuid tank is filled then only the rears will bleed.
 

Wighty

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Has the brake fluid level been checked as correct in the reservoir .....too much in there will stop the pistons retracting.
 
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SA1

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Where did the parts come from, are they genuine Mercedes purchased with the vin number .
Could be that the disc or pads are to thick. Also on some cars the backs calipers or discs are not made by the same maker as the fronts / like ATE on the front and Girling in some cases on the rear .And also the brake fluid fill tank is split in to 2 on some syestems and only the front section gets filled up , in this case only the front caliper will bleed . If the rear part of the fuid tank is filled then only the rears will bleed.

Hi Dreamer No2,

Oh dear - I hope that I have bought correctly ! - I got Brembro discs and pads for all 4 wheels. I got 32mm ventilated with min thickness of 29.4mm (as per my workshop manual) but not genuine Merc parts. I will check then against the old discs (I guess I should have done this before I started work).

I think that mine is a single fluid system master cylinder when I checked the manual - it's a w211, and 2 rear and 1 front bled ok.
 
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SA1

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Has the brake fluid level been checked as correct in the reservoir .....too much in there will stop the pistons retracting.

Hi Wighty,

I didn't know that - I had topped the reservoir up quite a bit as I had bled the brakes with a pressure bleeder. I am pretty sure that I rechecked the level, but it's a good point - I will double check.

Thanks to both of you - gives me a couple of things to think about and check.

Also - anyone know what size allen key for front ABS speed sensor?
 

DREAMER NO2

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The tank is one unit ,but it might have a double chamber inside and the fluid must be up to the full mark so the other chamber is filled .
 
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SA1

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SA1 I checked and i find that the disc size is 28mm from new number 211 421 98 12 And i think Brembos are 32mm
I was wrong about the size that I quoted - when I looked at the fitted disc it states on the disc 25.5 which is the same as the disc that I took off and is a 28mm disc like you said. The back pads look like they are Ok with a couple of mm gap so the back wheels spin ok. The pads on the front are pushed right up against the discs which is the problem. I have put in a new bleed screw in on the passenger front and bled that wheel, so all wheels have been bled now. I am wondering whether I might have to ring a mobile service who has Star system but that would be admitting defeat and having to pay someone. I think it might be something to do with the SBC reset procedure - maybe the pistons are not resetting - I have seen something on the net about spinning one wheel waiting and then spinning another wheel - looks a lot of messing about. Everything is clean and moves Ok as I cleaned everything as I was going along. I am renewing my insurance tomorrow - maybe could get Homestart breakdown service, but I am not sure whether they would look at a job which I have had a go at.
 

Naraic

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I'm lost. Pads should be touching the discs...at all times.
 

EmilysDad

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I'm lost. Pads should be touching the discs...at all times.

Is that not debatable? If they're touching the disc too much you'll be in the situation I was in (twice) this summer ie the disc gets mad hot. ;)
 

Blobcat

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On the face lift W211 without SBC the pads would touch touch the disc to dry the discs occasionally, I think SBC had the same function
 

DREAMER NO2

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Only thing i can think of is = when you retracted the pistons, or pushed them back in to the front caliper, was the top screwed on the brake fluid resevoir, if it was and the tank is full of fluid then the pistons wont go right back .
 

Naraic

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Is that not debatable? If they're touching the disc too much you'll be in the situation I was in (twice) this summer ie the disc gets mad hot. ;)
They touch, there is no debate. If they bind...you have problem. But definitely no gap as suggested by the OP.
 

Naraic

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On the face lift W211 without SBC the pads would touch touch the disc to dry the discs occasionally, I think SBC had the same function
They touch all the time there is no function which activates an occasional touch.
 


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