Do not try to use the air hammer as a wedge to pry or push the wheel hub free from the steering knuckle. It is virtually impossible to force the air hammer between the two components without damaging them.

I intentionally jacked up the car at the right front wheel—the one I didn’t think was making the noise—to get a baseline. I grabbed it at 6 and 12, rocked it, verified it was tight, and spun it. As expected, it was quiet.

On 1970s-era BMWs, there are inner and outer front wheel bearings with each sitting in its own race that’s pressed into the hub. Since the front discs on these cars sit on the inside surface of the hub, and since the bearings lift out of their races and present their greasy private parts to you when you pull the hub off the spindle, the advice is that, if there’s no documentation on how old the bearings are, to replace both sets of bearings on both sides when the front discs are replaced.

Instead, you can use the air hammer to rotate the wheel hub mounting flange in relation to the steering knuckle, while avoiding contact with the knuckle.  When the wheel hub starts to rotate, while the knuckle remains fixed in place, it will have broken free from the galvanic bond and will be much easier to remove.

To make sure this doesn’t happen again, I’m instituting a new system of checking the lug nuts on all four wheels after I’ve done any work where a car is jacked up for any reason.

After the recording session ended, I began driving back toward the highway. As I approached a small service station, I debated stopping to have them throw the car up on the lift and check it, but again, since the rumble remained low and constant, I headed home. Still, to err on the literal side of safety, I stayed in the right lane, turned the flashers on, and drove at 50 mph.

Bearingseizedon shaft

Rob Siegel has been writing the column The Hack Mechanic for Roundel Magazine for 35 years, and is the author of eight books available on Amazon. He currently owns thirteen cars. Yes, his wife knows about all of them.

Wheel hubs are made of high-strength steel and the steering knuckle they are attached to is generally made of aluminum. This leads to a process called galvanic corrosion (bimetal corrosion). Galvanic corrosion is a naturally occurring process in which two dissimilar metals react with each other, essentially welding the wheel hub to the steering knuckle during their normal service life.

I can only speculate what happened. Due to the space constraints in my garage, when I swap winter/summer wheels, I’ll usually pull one end of the car in, jack it up, swap both wheels, snug the lug nuts with a ratchet, let the car down, torque the nuts, air the tires, then pull the car out, flip it around, and do the other side. I must’ve gotten interrupted. Maybe I received a text I felt that I needed to respond to. Maybe my wife was leaving and I walked outside to kiss her goodbye. Maybe I had back pain and took a break. I don’t know.

Remember, if you damage adjacent components while replacing a wheel hub, the best case scenario is an extra call or visit to the auto part store as well as the job taking longer and costing more than planned. A much worse scenario is an angry customer or even a comeback if the damage isn’t identified before the vehicle leaves the shop. It pays to work smart!

Bearings seizedsymptoms

Still, to be careful, I pulled into the right lane, slowed down, and listened. The somewhat rapid onset was uncharacteristic of a wheel bearing, but the other symptoms fit. Since I had a recording appointment with a fiddle player, I preferred to keep going, unless of course I couldn’t for safety reasons. The rumbling remained at a constant low level, so I assumed it was a wheel bearing doing the soft failure thing, and continued on.

Bearings seizedmeaning

On newer BMWs, the front wheel bearings are very different than on the 1970s-era cars. About ten years ago, I owned a ’99 E39 528iT wagon that needed struts, control arms, and other front-end work. The E39’s wheel bearings are part of an assembly that includes the front hub—the wheel bearing assembly bolts to the steering knuckle, and the wheel bolts directly to the bearing assembly.

Whether you are an Automotive Technician or a DIYer, getting a job done in an efficient manner is important. One common issue that can occur when replacing a wheel hub assembly is difficulty separating the wheel hub assembly from the steering knuckle. Removing a stuck wheel hub can seem impossible at times. This quick tech tip should be helpful if you ever encounter this situation.

It is also recommended that you never use a torch to heat the steering knuckle. While heat can be helpful in installing and removing bearings, a torch does not provide the precision needed to heat only the necessary components. This can damage or distort the knuckle and ball joints, and lead to collateral damage to other vulnerable components on the steering, suspension and brakes.

Seizedroller bearing

I then jacked up the left front wheel and rocked it at 6 and 12. Yup, play. Then I spun it. Yup, rumbly. No doubt—a bad left wheel bearing. I set the car back down and began to walk back to the computer to order the bearings, vividly recalling how much of a pain in the butt they were to replace in the 528iT wagon ten years ago. I wondered if maybe still having those eight spare bearing bolts had made the whole thing a matter of fate.

In the repair world, there are “hard failures” and “soft failures.” Hard failures are things that instantly drag a car to a stop when they break. Broken ball joint? The worst type of hard failure—the front wheel folds under the fender like a broken ankle and you lose control of the car. Bad fuel pump? Usually a hard failure—it either pumps or it doesn’t. (Okay, there are some exceptions. The one my E39 wigged out on a low tank in hot weather, then recovered. I replaced it anyway.)

Rear wheel bearings on old BMWs are incredibly robust. I’ve only ever had one go bad. It was on a Bavaria that my wife and I took on vacation to Martha’s Vineyard in 1986. We were foolishly driving in near-hurricane conditions and got caught in a tidal surge on the road that runs on the barrier beach between Edgartown and Oak Bluffs and drove through water that was deeper than we expected (as I said, foolish). On the drive home, the right rear wheel bearing began rumbling ominously. At the time, I didn’t own the necessary bearing puller, and had to take the car into the late great Beaconwood Motors who had the back page ad of Roundel for a generation. It was one of a handful of repairs the past 40 years I’ve paid someone else to do.

Although bearing rumble is usually quite clear, part of testing for a bad wheel bearing is to jack the car up, set it on stands, grab the wheel at the 6:00 and 12:00 positions, and push-pull it. If you’re hands are at 3:00 and 9:00 instead, play in a front wheel can come from anything in the steering mechanism, but 6-and-12 play pretty much has to be coming from the wheel bearing. In an old-school car with adjustable wheel bearings, if there’s no rumble, you can try adjusting the bearing by pulling the cotter pin and moving the castellated nut by one notch, but play plus rumble equals bad.

Bearings seizedhow to fix

My ever-rational left-brain shot back indignantly. “You can’t be serious,” it sneered. “You actually had a wheel fall off that 1600 back in 1984. And you’ve had two close calls, both more recently than you’d like to admit. You know what loose lug nuts sound like, and this wasn’t it. And you learned your lesson. You conditioned yourself to always tighten lug nuts with a torque wrench. It’s not loose lug nuts. Really. It’s not. It can’t be. You are not that careless.”

Use of an induction heater to heat the wheel hub assembly is the preferred method over using a torch. This will allow you to apply heat strategically to the wheel hub to break up corrosion and help penetrating oils to penetrate deeper, while isolating related components from damage.

In contrast, soft failures are things that either give you ample warning before they fail completely, or their failure doesn’t immediately drag the car into the breakdown lane. A textbook soft failure is when the alternator or voltage regulator dies. Even though the battery is no longer being charged, the car can continue to run for some amount of time off the battery alone. On a vintage car like a 2002, you can likely drive for hours during daylight before the battery no longer has enough juice to light the spark plugs. On a late-model car loaded with electric motors and control modules, you might have more like fifteen minutes to an hour—enough to get to a rest area, possibly even a repair shop.

I was driving my 2003 E39 530i up to do some recording in Chelmsford, about 30 miles north of me, when I began to hear and feel a rumbling coming from the left front of the car. It ramped up over several minutes, but then plateaued. If it instead had gotten VERY loud VERY quickly, with obvious metal-smacking-against-metal instead of the more gentle rumble of a worn bearing, that would be the hallmark of loose lug nuts, something you need to pay attention to IMMEDIATELY because you may have only five or ten seconds before the wheel falls off.

Bearing removal Tricks

Wheelbearings seized

When encountering difficulty separating a Gen 3 wheel hub from a steering knuckle, you may be tempted to resort to brute force, in the form of a heavy hammer or other tool, to break the bond loose. Using a heavy hand tool is often ineffective at breaking the galvanic bond, but even worse, can damage the steering knuckle or other steering/suspension components, compounding the issue.

If you do not have an induction heater that works for a wheel end application, or you just need more muscle to separate the wheel hub from the knuckle, you can use an air hammer to help. When using an air hammer to loosen a wheel hub, the key is not how much force you are using; it is how you are applying that force.

When I arrived home, I pulled the nose of the car right into the garage, then hopped on the laptop to get a set of front wheel bearing on order. I looked on FCP Euro, and was more than a little surprised to find that a front wheel bearing kit with German FAG wheel bearing assemblies now cost $312. Of course, I still had that set of bolts, so I could save myself the $4.29 per bolt right there. I mean thirty-four bucks is thirty-four bucks, right? One FAG bearing was $139. I began entertaining replacing just the left bearing, then price-shopping other manufacturers, when I decided that I should be certain that the wheel bearing was really the problem.

How to remove bearing from shaft without puller

I snugged them down, grabbed the wheel at 6 and 12 and verified that the play was gone, spun it and verified that the noise was gone, let the car down off the jack, and tightened them up with a torque wrench.

Why do I have these and why can I lay my hands on them instantly? As Joseph Fiennes said in Shakespeare in Love, “It’s a mystery.”

And so, just to be certain, to placate my left brain and make sure I didn’t go to all that work unless it was absolutely necessary, I took a 1/2-inch ratchet and a 17mm socket and checked the wheel’s lug nuts.

Perhaps the down comforter of soft failures is a bad wheel bearing. Loss of lubrication will cause them to wear, resulting in a rumble that sometimes can be more felt than heard (they may also squeak or squeal), but the failure process is gradual. They’ll get louder as wear and play embrace each other in an ever-widening downward spiral, but you’d have to be an idiot not to hear it and address it, making outright failure rare. Wheel bearings are pretty robust in BMWs. After owning over 70 cars, I’ve only ever seen one wheel bearing that completely self-destructed—a ’67 2000CS I bought came with one that had destroyed the stub axle. I had to replace the entire front strut assembly.

And I’m going to have some sort of voodoo ceremony with that bag of Locktite-coated wheel bearing bolts. I can’t tell whether they were bad juju that triggered the problem or a talisman that warded off disaster, but clearly they played some role outside the normal Western vectors of Newtonian mechanics and Cartesian cause and effect. They deserve reverence.

Then I checked the lug nuts on the right front wheel. While none were loose to the point of being free-spinning, all were substantially below the 88 foot-pound torque spec. The rears were fine.

Rob’s newest book, The Best of The Hack Mechanic, is available here on Amazon, as are his seven other books. Signed copies can be ordered directly from Rob here.