CM project 2007 BMW 335i Coupé
Project BMW 335i
PART FOUR: Rob Hawkins heads down a metaphorical rabbit hole when he investigates the reason for our BMW’s dashboard lighting up like a Christmas tree.
Diagnostic issues are sometimes not so straightforward to fix and can have you running around in circles, which is exactly what I seem to have experienced recently. It all started with the dreaded ABS light being permanently displayed on the dashboard of the BMW 335i.
Whilst at my local garage (MJ Motors), who had helped to fix the handbrake issue outlined in the last issue of CM, we connected their diagnostic equipment and found a fault code relating to the nearside rear wheel speed sensor.
The fault codes were cleared, and we went for a test-drive with the diagnostic equipment still attached, enabling us to view live data and, in particular, assess the reading from the NSR wheel speed sensor, comparing it to the data for the OSR. Correct readings occasionally appeared, but more often than not, the wheel speed reading was zero.
The pattern of live data led MJ Motors’ mechanic Jacob to suspect that it was more than a failed wheel speed sensor. Perhaps the reluctor ring on the driveshaft had corroded, swollen and consequently failed.
Back at the workshop, Jacob had a collection of rear hub assemblies (with driveshafts) from various BMW models, which helped to confirm his suspicions. We could see how a swollen reluctor ring would result in an ABS issue, and it’s apparently a common problem on these vehicles.
When we looked underneath the rear of our own 335i, it was hard to see if there was a reluctor ring on the driveshaft because of a lack of space. We could see where the wheel speed sensor was fitted, but there wasn’t much room to look inside the back of the hub for a reluctor ring wrapped around the driveshaft. And the extent of the corrosion didn’t help.
With no workshop time available at MJ Motors, I needed to not only formulate a plan, but also find someone to help because I didn’t fancy the idea of tackling this on my driveway or inside my garage at home. Fortunately, Mark Shipman at AES came to the rescue, but wisely told me what could go wrong.
Mark’s initial concern was how difficult it was going to be to remove the old NSR driveshaft. He explained that the end of the driveshaft sometimes refuses to separate from the hub, so he has often removed the entire hub and driveshaft together, then used a hydraulic press to detach them. And this he warned, has involved leaving the assembly in the press overnight!
FIXING ABS FAULT
