S211/E320 ALL Brakes binding issue

[Nod]

Car is a 2004 E320 wagon, recently a motorcyclist whom was travelling behind me, tapped on my window to tell me my brake lights were kind of erratically coming on an off when clearly I was not applying the brakes, i.e going along with no reason to brake. I thought the car kind of felt slightly odd and when I stopped and felt the temperature of the discs they were well hot.
Strange thing is every wheel was like it, left and right, front and rear. Still doing it and seems to have got worse still.

You can feel the brake pedal also slightly stick on and I did try kind of pulling the pedal back up by hooking my toe behind it to see if it wasn't fully returning but seems it is, other than brakes still being jammed on.

Would this be Master cylinder/ Servo fault or could the SBC pump be causing the fault? Kind of reluctant to make any wrong decisions and do not want to go tearing into the mechanics of the brakes unless I am aiming in the right direction and actually fixing the problem, rather than just guessing and then having to hook upto STAR etc to fully bleed system etc. Seems the Master cylinder Servo setup is not that expensive to get a secondhand one, presume though I will need to use STAR though to rebleed it all if I try replacing that first?

Any help or advice greatly appreciated.

EDIT : After abit more research am I right in thinking the SBC pump unit replaced the Servo setup and therefore my car will not have a servo? So the fault is possibly the SBS unit that probably may need replacing?

 

[Blobcat]

Hello and welcome,

SBC will apply the brakes ever so slightly to dry the discs if the determines it’s raining. Wonder if the sensor has gone a bit do-lally ?

 

[Nod]

Hi Blobcat- thanks for your reply and help.
Yes, I did see that the SBC applied abit of brake when it rained. I reckon it may have been doing this intermittently for maybe longer than I realised. Reason being that on occasions the car did feel slightly like you were driving it against the brakes but maybe not quite enough for me to notice the brakes were on. However it seems that its now dragging much more and the fault has worsened, which is probably for the best as at least I can now try and rectify the issue, rather than being unaware of it. They are being applied with as much force that you can really tell that you are driving against the braking now, where as before it was harder to notice.
Also I recently became aware of the SBC HOLD and SBC STOP function, seems my car like many others the SBC is not available, i.e doesn't work basically.

EDIT : As it has become now, the brakes are more than just lightly on, (as they would be to dry the rain) -they were really boiling hot, not sure if the sensor can make them be applied with more force if its gone screwy? or if they will just be applied lightly- they are quite firmly engaged thus generating the heat so much.