Tapping noise from the rear
 

Discovered this noise a couple of days ago, coming from the rear, more prominent in the right side. It occurs only at low speeds, from about 6 mph to 25 mph (10-40 kmh). The noise sometimes seems to go away when just rolling without pressing the gas pedal but occurs again when braking or accelerating but this might not be 100 % generalized. I would describe the sound as something hitting something, with the frequency increasing with the speed. Also somewhat similar to the sound of bad cv axle.

I crawled under the car to look and noticed the heat shield of the exhaust in the rear was missing three fasteners and it was hitting the exhaust and the driveshaft. Put it back in place and went for a test drive and it seemed that the sound was not so prominent anymore but it was still there. Could have been just a coincidence though. Also inspected the CV boots in the rear and they all seemed to be intact and dry, no grease anywhere to be seen. Also haven't noticed any vibrations when driving the car.

I feel like it still could a bad CV axle, I guess they can go bad without having a torn CV boot but anything else to look for before I take the car to an indie? I will also do an another test drive today and let the wife drive the car me staying outside trying to pinpoint the location of the sound.

Tapping noise from the rear
 

If the sound is very metallic and a clean sound would almost describe as "tink tink tink". It's almost surely lose bolts in the GIUBO.

If it's giubo you can usually reproduce with the car in neutral and drive wheels off the ground and rotate the wheels= driveshaft.

It makes a distinct "tink" sound typically once or more per revolution often at the same spot so make a mark and watch it.

I looked (but no luck) for a YouTube video that I used as reference that was almost identical to the problem I fixed.

I only had to re torque the six bolts to spec and the problem went away. Hope it's as simple for you.

Also: do the math on the frequency; drive shaft turns 3.9 or 4.1x per wheel revolution.

2.225m=7.3 ft per revolution on the wheel. CV will usually cause sound 2/3x per rev

I was just going to suggest the guibo as well. At this day and age, anything rubber pretty much has to be replaced. I've learned that with my x5.

Okay after another test drive I can quite surely say the sound is coming from the passenger side rear wheel area, so I guess that rules out the giubo. Also filmed a short video of the sound where I accelerate from the stop to about 25 mph (40 kmh). As you can see the noise fades away when the speed increases and comes back when I let off the gas and let the car slow down. With a tape marking the spot, I was able to see that the noise occurs usually once per revolution of the wheel.

https://youtu.be/WfXYyW-WbTs

I had a similar thing end up being rust that got behind the dust shield. You prob have something inside the rotor/drum or between dust shield and rotor.

If you remove the rotor I bet you'll find a spot where the rust is evidently scraped away.

I hear a double tap that might show up as two high spots on the rotor.

Since it goes away faster it can also be on the outer edge of the rotor; as the rotor wears, sometimes the lip that grows on the end can touch parts of the caliper. Look for a scrape evidence.

Thanks for the tips, appreciate it. At least the rotor is very worn, so there definitely is a significant lip. Replacing them is in my to-do-list for the summer. Anyway, I will try to find time to check the rotor and surroundings this weekend, at the latest next week. I'll report back what I found.

The video is very helpful. Now we know it's somewhere on the wheel end. Using the black tape on the wheel really helps timing the ticking sound.

Check to see if where your e-brake hold downs go through the dust shield are still in good shape. That stamped "X" can rust out and your e brake shoes can move around. I had a very similar sound on my e34 and had to replace a wheel bearing just to get the dust shield/backing plate off. One other time I had a rock stuck between the rotor and backing plate and the noise went away when I pried the rock out.

An update to the situation, I decided to check the lug nuts of the wheel and all five of them were a bit loose. I was able to tighten all of them like 45-90 degrees. I don’t use a torque wrench for those, but have never had any issues with loose wheel nuts. I even double-checked all the wheels after changing to summer wheels and tires couple of weeks ago after having driven several hundred kilometers with them. Anyway, after the retightening, I have now driven over 300 km’s (190 miles) without the noise. Not really sure how the loose lug nuts would cause a sound like that but let’s hope that solved the issue. Or maybe there was something between the dust plate and rotor but it fell off by itself.

Well done!!

From one 4.6 owner to another, troubleshoot the simple/easy fixes first, especially if safety related. Always torque the wheel lugs, not fun if a wheel falls off. 3/8 and 1/2 in torque wrenches are a must have for DIYer.

You definitely need to torque your lugs. At the least I use torque sticks to get them close before a follow up. A primary point is to.get them tight enough to not loosen up. Even "snug" they will apply on the order of 40-50,000# of force but if as loose as you describe, for sure the hub to wheel surface could have moved a couple 1/1000" each rev and cause a tap. I heard a distinct double tap which could be two different lugs binding up and releasing.

Good share though. Somebody in the future will see this thread and check their lugs.

Well it was on the wheel end! Good catch. Luckily you didn't have any lug-bolts fall off during highspeed transit!

Yeah I should definitely have a torque wrench in my shopping list, already have a 1/4" one but not much of a use for car related stuff. Still wondering how I would have left the lugs so loose while even after the rechecking they were okay but I guess they were still a bit off which allowed them to loosen even more.

Torque wrench mandatory/big hoard of tools & parts optional
 

I've carried a "cheap" torque wrench in all my vehicles (my personal vehicles, not the ones the wife uses exclusively...she wouldn't be able to set the torque required) since the 1970's, after I had problems with lug nuts being too tight, or too loose, after using "4-way"s or a "jack-handle wheel lug wrench" (included, along with the jack, in most cars' equipment).

Several times I had found that after I had changed out a flat tire using those tools to loosen/tighten the lug nuts (or the bolts on my VW's), and then went to re-tighten them about 100 miles later (what my Grandfather taught me to do), they were either too tight or slightly loose, depending on my degree of aggravation when changing the flat tire. I just never was able to judge how much force to use.

At first, I carried a beam-style 1/2" torque wrench, but switched to cheap click-style wrenches when they started selling for under $50 USD. Since then, I've had no problems with wheels installed or tightened by myself.

However, I have had recent (and several times prior) bad experiences with lug nuts/bolts that were too tight to remove easily, that had been installed by tire shops presumably with powerful air impacts. I usually found my truck wheels had been overtightened way past the 140 ft-lbs required, so I added a long-handle 1/2" breaker bar (with an extension tube for added power) to my truck equipment. The recent https://xoutpost.com/bmw-sav-forums/...bolts-e53.html problem I had with my first flat on the X5 prompted me to add a breaker bar and extension tube to the growing assortment of tools I have in the trunk (including std. BMW tire-changing equipt.), all in various toolbags and boxes:

• two more jacks,
• two jack-stands,
• a decent torque wrench,
• full sets of metric sockets and tork sockets,
• misc. other hand tools,
• two worklights,
• fender cover, ground cloth(s), beach towels, work gloves, hand towels, hand cleaner,
• a laser temp gun,
• two hand-held scan tools (Foxwell NT510 Elite and Innova 3101i),
• two Android/Bluetooth OBD2 dongles, OBDLink LX and BAFX for Torque Pro, OBDLink apps
• "OHP INPA Cable FTDI FT232RL USB OBD2 for BMW Diagnostic Coding | K Line" , used for the Android apps Bimmertool Pro and Deep OBD,
• dedicated spare phone for Android OBD2 app usage (8" Android tablet, too, if traveling 100+ miles from home, also for OBD2 and offline maps)
• panel fasteners,
• spare fuses+terminals+extra wiring kit,
• 1 gallon of pre-mixed blue coolant,
• 10 quarts of Castrol 5W-40 Euro/Hi-mileage/LL oil + filter+ spare drain plug,
• many miscellaneous unnamed items & tools,
• even a 6"Hx10"Wx18"L treated wooden block (for a solid footing for my choice of jack).

Probably 200 lbs of gear. Overkill, just in case I have a problem away from my real tool sets, at the house.

I've been amazed over the years at what even reputable shops can miss. I think lot has to do with them moving too fast, confirmation bias, etc., and some with unfamiliarity, especially as vehicles age. These are the very reasons pilots use checklists!

Many years ago I had a reputable shop do some front suspension work and a valley pan in my X5 and they neglected to torque the subframe stiffener bolts. This will get your attention on the road.

Did you check to see if the loose wheel deformed the lug holes in the wheel?

I guess it can happen to any of us, I just got to use torque wrench next time. :D

Actually I didn’t, will do tomorrow, thanks for the heads up!

140Nm (~105ft.lbs)?

140ft.lbs is VERY tight- at least on our cars! ;)

(Maybe you are referencing a larger vehicle spec.)

unclear reference to a larger truck
 

I guess I didn't make the reference clear; the truck that I referred to was my '04 Chevy 2500HD WT, with eight-lug wheels. It does require 140 ft-lbs torque, which seems to have been exceeded on all three sets of new
tires I've had installed at Discount Tire and NTB. That's when I started carrying the breaker bar.

Previously, 1/2" diameter, 5-lug and even 6-lug Chevy trucks only required 90 ft-lbs (actually 65-90, prior to the mid-70's), and when they were overtightened, I could still get them loose. But, when the lug bolts/nuts went to 9/16" on the eight-lug wheels, it seems all the tire techs decided to use their most powerful impacts to secure them. I never expected the same on the X5.

I would check but most of the weight should be carried by the hub center even with a little looseness it should be very subtle if the cones get oblique.

I would check regardless of the odds.