Removing/cleaning the dreaded ABS wheel speed sensors
Not exactly this week – but during the past few weeks. Had issues with the dreaded ABS light coming on intermittently – which was pinpointed to a front wheel speed sensor. Decided to start at the back after refurbing the rear callipers.
For those who do not already know, these plastic sensors fit very snuggly into holes at the back of the hub. The first problem is the little, single allen key bolts securing them gets very rusty so the correct size allen key just spins and does not work. However, my youngest son who is an aircraft engineer, used the old trick he has learned which is to gently hammer in a slightly over-sized torx which provides enough torque to remove the bolt.
The second problem is that as these things fit snuggly into their holes, where they have sat for 15+ years, they are tricky to remove and require liberal application of WD40 or similar and to be gently prised & twisted out. They are also made of plastic and so are a bit delicate. The rears are barrel shaped and weren’t too grubby – but we gave them a good clean, light greasing on their sides with non-metallic, brake, anti-seize lube before replacing.
The main problem was removing the front sensors. These are longer with a square section on the end. The first was very difficult to remove and was very dirty. It was cleaned and replaced as above. The “fun” was reserved for the final front sensor. It would not budge and so we had to resort to drilling and picking it out in pieces – being careful not to let any pieces fall inside the hub. The good news is that similar sensors appear to have been used widely across BMW cars and so there is a plentiful aftermarket supply so we purchased a Meyle one which only cost £17.95. The ABS light has now gone out and stayed out.