How to disable a R56 Mini Cooper brake wear sensor indicator
Back in November I replaced the brake rotors and pads on all four corners of my ‘08 Mini Cooper. Part of the process involves replacing the wear sensors on the front left and right rear calipers. I ordered new Mini OEM sensors and dutifully replaced them both. BTW the right rear sensor took about as long to replace as all four sets of rotors and pads :-/
During my 1,500 mile drive up from Sarasota, FL to Watertown, NY in March the amber brake warning lamp and service indicator both suddenly starting coming on every time I started the car (as shown above) – with the amber brake warning lamp staying lit all the time. I consulted the manual and discovered that this was the warning indication for the brake wear sensors. Since I had just replaced the brake pads I knew they weren’t worn down that far already and suspected there was something else afoot. Sure enough, a quick visual inspection revealed the wire to the rear wear sensor detached from the sensor block and sticking out behind the rear caliper:
Now, all these sensors are is a loop of wire that runs through a block of high temp material that plugs into the brake pad. The system looks for a break in the current flowing through the simple circuit to indicate that the block has worn down far enough to sever the wire. Apparently it is quite common for these sensors on Minis and BMWs to come loose and fail like this. You can see here where the sensor is supposed to be plugged into the rear brake pad/caliper assembly:
Since March I have simply been doing my best to ignore the light while I waited for my floor jack and tools to arrive at my new house in NY. That happened three weeks ago but now I’ve decided to trade the Mini in for a 4WD SUV that’s better suited for the winter weather up here. So, I’m not too keen to go through the expense, hassle and bloody knuckles of buying and replacing the broken sensor, but I do want the light to be off when I get my car evaluated for trade-in value. So, I simply jacked up the car, pulled off the rear wheel and connected the two leads together to complete the circuit.
After stripping away the outer insulation I found two small wires:
All I did was strip about 1/2″ of insulation off each wire and twist them together:
Then I folded the extra wire up and and sealed it all with a length of heat shrink tubing:
If you are doing this as a permanent modification (say for a track day car or big brake upgrade) I might suggest cutting the brake wear sensor cable off somewhere on the body and then solder the connection before applying heat shrink tubing to create a more durable modification. Just be sure to cut the replaceable portion of the wear sensor wiring assembly and NOT your main wiring harness! If you find that splicing the wires doesn’t solve the problem (i.e.: the dash warning light doesn’t turn off), be sure to check both sensors and the plugs where the sensors connect to the wiring harness. Also, check the brake fluid level as that can create a similar warning indication (and really IS a problem).
I left mine pretty visible as I wanted it to be noticeable so that the next time the brakes are serviced the mechanic will see what I’ve done and (hopefully) think to replace the wear sensor.
The end result is a gloriously warning-light-free dash. The service indicator is also gone at start-up:
And just in case anyone is thinking that I have created some kind of safety issue for the next owner of this car, rest assured. The Cooper has a mileage based brake service indicator that will alert the driver in plenty of time before the brakes are warn down too far. In fact, the wear sensors are designed as more of a last warning before the mechanical wear limit indicators built into the pads start squealing (and gouging the rotors). Nobody should let their brakes go that far!
Hopefully this will help me eek out a few extra hundred bucks on my trade-in. Stay tuned to find out what I buy next!