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

[Blobcat]

They touch all the time there is no function which activates an occasional touch.

On a wet road surface the system metes out short brake impulses at regular intervals to ensure that the water film on the brake discs dries off and that SBC can always operate with optimum effectiveness.

This automatic dry-braking function is activated at regular intervals when the car’s windscreen wipers are running.

The driver does not even notice these ultra-precise brake impulses.

 

[Naraic]

OK...I was wrong re SBC.

However...does this also mean the pads are not touching the discs when the brakes are not being applied? Or does it mean it simply "dabs" the brakes at intervals?

 

[EmilysDad]

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 .

They will .... the excess fluid finds its way out of the reservoir via the vent hole in the cap

 

[Blobcat]

OK...I was wrong re SBC.

However...does this also mean the pads are not touching the discs when the brakes are not being applied? Or does it mean it simply "dabs" the brakes at intervals?

I had the follow up system and it said the same as SBC it sensed if the discs were wet (guess by the rain sensor and windscreen wipers working...) and then ever so gently applied the brakes to dry the discs. I never felt it working in my W211 but had no reason to disbelieve the system. The pads will only ever be just off the discs by a very small fraction in use so I don't really see this feature as anything other than a but of marketing - it might fractionally reduce stopping distances and I suppose Mercedes did the tests and made it happen.

 

[DREAMER NO2]

Put the old pads back in simple .Then give it a spin out

 

[DREAMER NO2]

They will .... the excess fluid finds its way out of the reservoir via the vent hole in the cap

But not quick enough .And another is the flexi hoses get damaged by clamping them , but on both front calipers i dont think its that . This is hard to fix ,, as we are not there to check it out . Like one chap that said his wheel would not go on only to find his jack was so close to the caliper it was stopping the wheel for contacting the hub. Other way out is throw all the old parts back on to the car .Then if it works the new parts were not the right type or size for the model you have.Said before ..

 

[SA1]

Hi everyone,
I was under the impression that there needed to be a small gap between the disc and pads because after I started the car and tried to drive it a few metres the steering got real heavy (plus ABS light on and ESP error on the dash) and I figured that the brakes were binding and that I had not done the SBC activation correctly. I decided to deactivate and then reactivate the system again but this time I put the car in neutral (instead of Park) and went via the SBC reactivation via repair (instead of maintenance) change brake pads using my iCarSoft 11 diagnostic, and this time it asked me after a while to turn off ignition, turn on ignition, etc - steps which I wasn't asked previously when trying to reactivate. I think putting the car in neutral and following these steps was the better method as it also cleared any faults which were previously there. I thought I had just about solved it all, and after putting all my tools away, thinking that I could happily drive off into the distance, I was again disappointed to feel the heavy steering and the ABS light and ESP message coming on again. I am not sure what the heavy steering means, but during all this time I realized that my battery depleted a bit - I had a spare which I put on but it is only reading 12.4V after running 10 mins (alternator is new) - so even though the pads look like they are touching the disc I am beginning to think that this is normal (especially as the wheels spin around when jacked up and in neutral) and that the car didn't get moving due to my battery power being a bit low and may have meant that the power steering electrics for the pump wasn't at high enough voltage, although I got no battery error on the dash or on my diagnostic. Anyway that's what I'm hoping - I will get another battery with full voltage and see what happens and then send another message. I didn't adjust the parking brake after fitting the rear discs as I tried it one time and they seem to hold ok. The only error message that I have now is '930E synchronisation of the DTC memory cannot be ensured'.

 

[Botus]

you won't see a gap, but there is one.... but its a few thou at best

the simple check is with a wheel off the ground, light pedal pressure the wheel shouldn't move, take foot off off and should spin freely and carry on half a turn or so.. if not its pistons or sliding caliper body is stuck (with normal brakes) with SBC who knows

SBC is supposed to wipe pads every now and then, never noticed a car get funny with wet weather... but on a bike cold discs and damp conditions used to be dangerous as hell... they basically stop working and by the time they start to come back into play you already hit whatever you wanted to avoid

 

[SA1]

Hi All,

I put on a fully charged battery and got the same as before with ABS,ESP and yellow warning triangle flashing on and off, and heavy steering at v low speed (which was worrying and not sure why that would happen - related to steering angle sensor - written lower down?). I guess I should have known this would happen as at least with my 12.4 v battery, the alternator would have charged it to 14 V - anyway at least I can rule out any battery issues now.

The next day I looked up about ESP and found some information about the steering angle sensor and how you can re-calibrate this by turning the steering wheel lock to lock. I drove the car at 5 mph and did the lock to lock a few times with no heavy steering. I turned off the engine, attached the iCarSoft and there were no system diagnosis error messages apart from the one about 930E etc., but when I went into just the ESP menu, I had various errors related to speed sensors (I had disconnected these previously to check them), stop lamp switch no contact, ESP switch off rotary speed and lateral acceleration sensor defective. As I assumed these were all previous errors which happened whist I was trying to find out the problems, I decided to delete them all and none have come back since.

So I just have the flashing yellow warning triangle now when I drive above 5 mph - I am weary about driving it more than a few metres as this is a brake issue but probably the ABS light would come on as the yellow warning lamp is soon accompanied by deactivation of the ESP.

I decided to look at movement of the wheels off the ground. Jacked up each wheel in turn, and put in Park - each of the front wheels moved just over half a turn when pushed with one hand. When put in neutral, each front wheel moved one full turn with one hand pushing. In neutral for each of the rear wheels, I couldn't push either wheel with one hand, but needed two hands and each wheel moved about 1/4 of a turn.

I would appreciate it if someone could check on their car and tell me if they get the same as the above for all their wheels and whether what I am experiencing with the car jacked and with automatic gearbox in neutral is normal - I was thinking that if this is not usual then it might be the cause of the flickering yellow warning triangle?

Regarding the back brakes, I haven't adjusted the parking brake since I put on the new discs as I read that it was self adjusting - but did wonder whether I should do this.

Botus - thanks I will try your check tomorrow - that's the front brakes and in neutral yes?

I have also ordered a dial gauge to check the front wheel bearings which I did, as I set it manually, to give me peace of mind that I did it correctly which hopefully will give me more accuracy than doing it without an instrument.

Thanks.

 

[onefortheroad]

Sounds to me like you have upset one of the front wheel speed sensors. Or a pick up ring in the hub .....

 

[SA1]

Sounds to me like you have upset one of the front wheel speed sensors. Or a pick up ring in the hub .....

Possibly - I did the ohms test by disconnecting the plug behind the wheel arch plastic liner cover and got 9M ohms. I had read that the reading is meant to be a lot lower than that, but I got the same for the other front wheel sensor and thought it unlikely both sensors had faults. I didn't do the voltage test though, which I have since read is a more reliable check of the sensor.

I might drive the car a few mph and see if I can find a suitable live data menu on my icarsoft - to double check. I guess I could also swap the sensors to see what I get - haven't checked the back sensors - maybe do those as well, but might not be able to swap as I think they are different on back compared with front. The ring seems not to be in the hub itself (I couldn't see any connectors on it) so thought might not be due to wheel bearings (especially as new bearings as well).

Do you think the wheel movement is Ok when jacked up?

Thanks.

 

[onefortheroad]

Possibly - I did the ohms test by disconnecting the plug behind the wheel arch plastic liner cover and got 9M ohms. I had read that the reading is meant to be a lot lower than that, but I got the same for the other front wheel sensor and thought it unlikely both sensors had faults. I didn't do the voltage test though, which I have since read is a more reliable check of the sensor.

I might drive the car a few mph and see if I can find a suitable live data menu on my icarsoft - to double check. I guess I could also swap the sensors to see what I get - haven't checked the back sensors - maybe do those as well, but might not be able to swap as I think they are different on back compared with front. The ring seems not to be in the hub itself (I couldn't see any connectors on it) so thought might not be due to wheel bearings (especially as new bearings as well).

Do you think the wheel movement is Ok when jacked up?

Thanks.

new bearings ? was that the whole hub or just a bearing kit. . the bearing grease seal on the inboard bearing in the hub also acts as a magnetic pick up ring for abs,esp and power steering speed sence , if the gap from sensor to pick up ring is too great above 10 mph the car goes nuts . might be worth looking into , if the seal used was anything else other than a dealer part , id imagine thats your problem area. yes the wheel movement sounds ok , they are meant to grab ever so slightly , esp the rears also the handbrake shoes will need adjusting up to, if you backed off the shoes to fit new discs , its not self adjusting , i thought mine were good as i couldnt budge the wheel with handbrake on but it didnt pass the mot test and required another 2 or 3 notches on the star wheel . .

 

[SA1]

I bought Meyle bearing kits for both front sides. I replaced all the races and pushed the bearing into the large race and put on the new grease seals flush with the hub so I can't see how I could alter the gap if everything fitted together tightly?

I didn't back off the handbrake to take the rear discs off; they came off easily. With the handbrake off and in neutral can you move the rear wheels by much with each jacked up - is it the same as mine?

I will investigate the sensors today.

 

[onefortheroad]

the bearings maybe tight on the shaft and sitting a mm too far away from the sensor , or the pick up rings are being rejected by the sensor. the front wheels are meant to spin freely , the rears are meant to grab ever so slightly until the handbrake shoes wear away ,leaving you with the ideal setting. if you didnt need to retract the shoes on removal of the discs , then they clearly are in need of adjustment .

 

[alexanderfoti]

+1 as others say, your heavy steering etc is down to a wheel speed sensor fault probably. Check the wheel speeds whilst driving via actual values.

Adjustment procedure when fitting rear discs is to wind the adjuster out until you cannot rotate the disk, then wind the adjuster in 2-3 turns. This sets the right clearance on the handbrake pads.

 

[SA1]

+1 as others say, your heavy steering etc is down to a wheel speed sensor fault probably. Check the wheel speeds whilst driving via actual values.

Adjustment procedure when fitting rear discs is to wind the adjuster out until you cannot rotate the disk, then wind the adjuster in 2-3 turns. This sets the right clearance on the handbrake pads.

Thanks Alexander for the advice regarding the Parking brake adjustment.

Regarding the sensors check - I went into the ESP menu which allowed me to look at the speed sensors rpm, and drove the car a few mph. Sensors 1,2,3 registered similar rpm values, but sensor 4 (L6/4) was zero. This sensor is RHS rear. I swapped the rear sensors around, but got the same result, indicating that the sensors were Ok but still something amiss as getting no speed value for the RHS rear wheel. The fact that I got no errors in the main diagnostic system menu also bears out that the sensors are Ok.

Just still getting the 930E error mentioned above but unsure whether this has anything to do with the issue above - this is the only error I'm getting.

All comments regarding my next likely step would be appreciated !

 

[SA1]

Does this mean I may have a problem with the magnetic ring in the RHS wheel bearing?
I guess it could also be the rear reluctor ring but it seems very coincidental that this fault should just appear now.

The reason I did the wheel bearings in the first place was due to an advisory of 'slight play in front wheel bearings' so I thought it convenient to do them at the same time as the brakes, also that my car has just done 190k.
Could it be the magnetic part in the rear wheel bearing - but again would be a bit of a coincidence to find the fault at this time when doing this work when previously all was ok with rear bearings.

For some reason my SBC is showing 50% when I run my diagnostic, but with no error messages.

 

[Naraic]

How did you "tighten" the bearings?

 

[onefortheroad]

Most mercs have slight play in the front bearings . this play goes away when the bearings heat up. Best ignored when mot testers quote it. Most don't understand how they are set up.

 

[SA1]

How did you "tighten" the bearings?

Hi Naraic,

I watched a few utube videos and proceeded accordingly, set it so that the hub wasn't free spinning but offered some play when spun - have a video but not sure how to load it on this site (quick time movie with windows media player) - could you tell me how to do this?

Bought a dial gauge in the meantime so will probably use this to double check (or after driving for 50-100 miles) as it will probably be better than just a manual adjustment which I carried out.