Project E36 M3 - Front Wheel Bearings September 15 2013, 2 Comments
A nasty whirring sound had started to develop on the front wheel, and it sounded like the wheel bearing was on its last legs. I placed an order for a wheel bearing kit, and when they came in, I went to work. With the right tools, it is not a difficult job. In a nutshell, the process involves stripping the brake caliper and brake rotor off, which gives us access to the wheel bearing. Keep in mind that there are a few uncommon tools that you will need. In regular Red Eye Garage fashion, this was a nighttime wrenching session.
The first step is to get the car up in the air and take the wheel off. Next, the anti-rattle clip is removed to release the tension on the brake caliper. I used the red screwdriver against the rotor hat to apply rearward pressure on the clip while the blue screwdriver coaxes the clip out of the mounting holes.
The caliper is held on with two bolts. An allen socket on a ratchet was my weapon of choice. An allen key works too if you can get enough torque on it. Another way to do this is to use mallet blows on an allen key to generate the initial loosening torque.
Once the bolts are loosened, work the caliper off of the rotor. I like to pull the caliper outboard for a long 20-count. During this time, the piston in the caliper will get pushed back into the caliper ever so slowly. This should provide enough clearance to remove the caliper. Once the caliper is removed, hang it up with a rope or equivalent so that the brake line isn't supporting the full weight of the caliper.
To get to the wheel nut, you need to pop off the dust cover. It is difficult to remove it without damaging it, so I always order a new one when performing this job. I use a screwdriver driven by a mallet. Get under the lip of the cover, and then start prying around the perimeter until it comes off.
With the dust cap off, you can see the huge nut that holds the wheel bearing onto the spindle. Knock back the indention in the wheel nut with a screwdriver and mallet.
The nut is a 46 mm nut, which is difficult to remove without a 46 mm socket. The outer diameter of the socket I bought was initially too big to fit inside the hub, so I had to use an angle grinder to convert the socket into a thin-walled socket.
The torque spec on this nut is 300 Newton-meters (221 ft-lbs), so depending on how strong you are, a breaker bar may be useful. The breaker bar I used is about 1 meter long. After you remove the wheel bearing nut, loosen, but don't remove the bolt that holds the rotor to the hub. In order to do this, you may need to lock the rotor from spinning. I wedged a screwdriver into a vane of the brake rotor and supported it against the brake caliper bracket. Once the bolt is loose, remove the caliper bracket first, and then fully remove the rotor bolt to remove the brake rotor.
The wheel bearing is now accessible. Use a puller to pull the bearing out. If you are lucky, the inner race of the bearing and the outer race will stay together and it will all come out as one assembly.
In this case, the bearing decided to be racist, and the inner and outer races have separated. The outer part of the bearing came off, while the inner race remained on the spindle. We need to get the inner race off of the spindle too, but the inner race is sometimes difficult for the puller to grip. I used a trick where I employed baling wire to pull the jaws of the puller together. I used pliers to twist the wire and provide tension while working the puller. Grinding the jaws to bite better may help too. The other way to do this is to carefully cut a groove in the inner race in the inboard/outboard direction with a Dremel tool. Be careful not to cut through the race completely, since you can damage the spindle if you go all the way through. Take a chisel and try to get the race to split along the groove.
This is how the spindle looks like with the wheel bearing removed. Now, we just have to install the new one.
The new wheel bearing gets hammered back onto the spindle, but the installation force can break the bearing if the force isn't applied to the inner race only. I used a socket that was slightly smaller than the diameter of the inner bearing and a mallet to drive the bearing onto the spindle. It takes a few hard whacks to get it going. Apply a thin layer of high pressure grease to the spindle to aid in installation. Make sure the installation orientation is correct, or you will likely destroy your bearing if you have to remove it.
You only have to drive the wheel bearing far enough for the wheel bearing nut to get started. Tightening the nut will drive the wheel bearing in the rest of the way. The torque spec is 300 Newton-meters (221 foot-lbs).
Punch divots in the wheel bearing so that the wheel bearing can't back out. If the nut manages to back out, the wheel can come off the car while driving. You can use a screwdriver and mallet, but I find a chisel works a little better.
Install a new dust cap by tapping the center of it with a mallet. The rest of the reassembly is straightforward and you should be able to manage getting everything back together if you managed to get it apart. Be sure to clean and degrease the brake rotors if you managed to get them dirty. Now our car has fresh bearings and no noises.