Diagnosing bearing noise

[JHZR2]

Vehicle is a 91 bmw 318i, just shy of 170k. Runs and drives perfect. Was creeping along today on some very smooth/new asphalt, really slow, and observed some noise. As I'd roll along, I'd hear a tap-tap-tap-tap. I could hear it with the car in neutral or in gear, and regardless of clutch position. As soon as if be moving under power or even faster than a few mph coasting, it wouldn't be audible, or at least road/engine noise would drown it out.

But another clue, sometimes when driving at highway speeds, I'll notice a similar tap-tap-tap-tap when cruising. But only sometimes. And to make it odd, at speed I could be doing 65 or 85 and the period for it is always about a second from one series to the next.

Didn't really time it today.

I had one bad wheel bearing, but it have a groan on the highway. I'm guessing this is something else, maybe a bad vc joint or driveshaft bearing?

It's really hard to trace because if I drive with the windows down or door open, I can't hear it, so I have to roll slow with the doors closed. And it's tough to track.

How would I get started? I'd imagine up on a rack would be useless unless something has a lot of play, no?

 

[gman2304]

I heard something similar last week and I had a 10 mm bolt in the center of the right front tire. Put it on a rack and have someone gently engage the transmission and go through the gears while somebody under the car listens for the tap. Good luck.

 

[Trav]

Does this noise seem to be one tap/click per tire rotation or more?
It doesn't sound like typical wheel bearing noise but more like an outer half shaft bearing.
Even though the boot isn't torn after so many years the grease can deteriorate and the joint can wear.

Wheel bearing noise tend to get louder over a very short time, if its a joint they can go on for a long time without getting much louder. The inner joint is likely to cause vibration and possibly some clunking noises.

Definitely doesn't sound like a bad guibo noise. Make sure there is nothing in a tire or anything hitting the brake dust shield. You just did brakes on this one right?

Just throwing a guess out, without hearing it i really have no idea.
Someone sitting in the back seat then passengers seat can sometimes hear things you cant from the drivers seat. That's where i would start.

 

[Merkava_4]

When my wheel bearing went out, it sounded like big knobby Jeep tires going down the road. When I'd jerk the steering wheel real quick, the noise would stop for a half second. I imagine all cars have their own sound though.

 

[andyd]

Is the drive shaft encased in an aluminum heat shield ? When replacing the cat-back recently I bent it into the shaft some where. It was tapping something awful.

 

[spasm3]

I have experienced an inner tie rod making noise and acutally putting feedback to the steering wheel that felt like a tire out of balance. Ball joints, tie rods and wheel bearings all become suspect at high mileage.

 

[Vikas]

As far as I can remember wheel bearing noise is similar to airplane taking off rather than helicopter It is a constant loud hum. If it is clicking, then it is most likely the CV joint or an equivalent drive-shaft. In any case, you will have enough warning until the noise makes it obvious as to which part needs to be replaced.