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-   -   Sounds From the Rear: Explained (http://www.bimmerfest.com/forums/showthread.php?t=220181)

SCANDINAVIAN13 07-26-2007 07:07 AM

Sounds From the Rear: Explained
 
I think I've gone through pretty much all of the problems you can have with the rear end of the car that will make distinctive noises, so I'm going to lay some of them out for anyone who has problems in the future.

I'll start with the most severe:

My car sounds like...

...a helicopter:
Pull over now!!! The most probable cause of the sound is one or several loose lugs. Stop the car, bust out the BMW tool kit (the tire iron is actually over on the battery cover) and tighten all of the offending lugs. While you're at it, go ahead and check all of the rest of the lugs too. If the lugs work their way out far enough, the sound will get worse and the shaking will pick up. Eventually the lugs will snap and you'll note you'll be riding a bit lower on that side. By then, it's generally a bit too late - your car's on the ground.

...it has metal scraping around in back:
It might be that the rear shock mount (RSM) has failed. This failure, however might not have occurred at the shock mount itself, unfortunately. The metal scraping and knocking could mean the failure occurred at the frame mount. This is going to require some metal work to fix. Plan on spending a good amount on fixing it.
To prevent this, upgrade your shock mounts and re-enforce them! Re-enforcement plates are available at BavAuto, among other BMW parts shops.

...there's a slight knocking or squeak in back:
As mentioned above, there is probably a problem with the RSM. A knock means that the RSM has probably failed and the upper mount of the shock is just knocking around freely. Squeaking generally only occurs when the roads are wet, but can occur at other times, and generally means the same thing. Both the knocking and squeaking should co-incide with suspension actions, such as driving over bumps, or rough roads. This problem isn't as urgent as the above-mentioned, but since the mount has failed, it's possible that moisture can now get into the car, which can cause other problems. Get new rear shock mounts. Meyle makes a heavy-duty RSM that resists push through failures (most common type), yet retains the stock feel, unlike many of the urethane upgrades. If you're going performance, now is a good time to upgrade to urethane. When you replace the shock mounts, don't forget to buy a re-enforcement plate! Replacement RSMs are available at most all BMW part shops, and re-enforcement plates can be found at BavAuto, and maybe Pelican.

...it's running on off-road tires:
This is most likely a failure of the rear wheel bearing (RWB). The rear wheel bearing failure's sound can range from a grumble, to a growl, to a roar. When it gets bad, it will sound like you're riding in a Jeep with huge off-road tires. The sound will follow your car's speed, not the engine RPM. Generally, as you get faster, the sound gets louder. This is not always the case, however, as sometimes there is a point at which the sound will die down some. To check the speed correlation, bring the car up to highway speed and press the clutch pedal (if you're an AT, put the car in N - this is illegal in many states, so watch yourself) to let the engine spool down to idle, while your speed remains relatively high. If the sound remains strong, it's most likely the bearing. If the sound dies with the engine RPM, you've got something else wrong.
RWB fixes are nasty! They aren't super-urgent, but be aware that if the bearing finally fails completely and locks, you're not going to be getting anywhere very quickly and you'll probably need to replace the tire that just got dragged until you stopped. I drove on mine for a while before I replaced it; some 4,000mi, I think. That's not the smartest option, but I needed to save up for the parts and tool.

DIY GUYS: This fix is time-consuming and expensive! The tool to remove and press the bearings is around $250 itself. The bearings are around $30 each. If you have a while (and the patience!!) to do this job, this is your best option. You can do both bearings on the rear axle for the price of what most garages charge for one. Expect hang-ups if your car has not had much service in the rear. Frozen bolts, hubs and rotors all slow progress and are a general pain. Once you get it done, however, your car will sound like new again. The tool and parts are available at Pelican Parts (they have the best prices on this job, believe you me!).
You will need:
2 RWBs, 2 Circlips, 2 New Rotor Screws (one-use part, don't re-use the old one!) and the bearing press. A Bentley Manual is an absolute must! If you don't have one, PM me and I'll send you my write-up with alternatives, should one of the options not work.

NON-DIY GUYS: This fix is expensive! Expect the shop to charge around $300-350 (that's at independent shops). It will be a bit less on the second bearing if you're getting both done. BE AWARE that some BMW specialty shops may try and screw you. One BMW shop that I trusted quoted me at 7 hours of labour, plus over-priced parts, so watch yourself. I could've gotten the job done in 1 hour a side if I had a lift and shop tools. Seven is about what it took me in the end with socket wrenches, jack stands and a rubber mallet.

...it's hissing:
First, check and make sure you don't have a hole in your tires. If that's not the case, and it sounds more sandpaper-ish than high-pressure air, then it's probably something rubbing. More specifically, the brake rotor shields. If it's very light-sounding, it's probably fine. If it's more gouging or metallic-sounding, you should probably try to re-bend the shield so it's not rubbing so intensely. The best bet, however is just getting them replaced. The shields themselves are not too expensive, but the job is similar to the rear wheel bearing job, as the rotor will need to be removed and the hub will need to be pressed off to get to the brake shield. I haven't gotten a quote from a shop, but I'd expect labour to be the main cost in this fix.


I hope this clears up some of your sound worries. Good luck with the fixes!

Pirate_copy 07-26-2007 07:13 AM

Great thread buddy

Will try to get it sticky'd!

SCANDINAVIAN13 07-26-2007 07:18 AM

Awesome! Thanks Pete!

1canary 07-26-2007 09:38 AM

For what it's worth, replacing my OSF disc shield cost me 232 including new bearings at my local garage. Probably could have got it done a little cheaper but not enough time to look around, which I feel is usually essential.
Just so you have a guide price:thumbup:

320what? 07-26-2007 01:08 PM

whats the noise when driving on bad road like plastic beats creaking from the back? :) in sedan.

1canary 07-26-2007 02:15 PM

Not sure. Did have similar noise myself but more tinny than plastic sounding. Turned out to be the dust protection tube on shocker was split and rattling against the shocker. It then did it no matter what road surface I was on. Bl**dy annoying.

oakley 11-01-2007 12:41 AM

If only I had read the helicopter noise bit a few years back on my first bimmer before the wheel sheared off on the motorway destroying both my car and my insurance!! (not to mention the pants of both myself and passenger!!)

M Jakubowski 11-11-2007 08:00 AM

Great text, congratulations!

spanieldecks 11-26-2007 06:02 AM

'squeak'?
 
Hey there, great thread. I'm currently troubleshooting a load of small noises in a recently acquired '97 M3. Here's a tip for y'all, check that the door trims are tight against the panel. New plastic clips can be bought from the BMW stealer of pence... and removed door trim rattles instantly! When doing this, don't be afraid to 'muscle' the panel off in the first place.. it's damn tight"

I have a 'squeak' when pulling away or accelerating from it sounds like the rear seat. or perhaps below it. No knocks or anything when driving (had new bushes to fix that), just a one off 'squeak' when pulling away. even had the wife drive it with the rear seats out so that I could locate it... any ideas or similar experiences?

tonyyank 12-05-2007 07:05 PM

How much to fix the failure occurred at the frame mount.... I know I have this problem.

And if its not fixed, will it get worse ? Will I die one day driving down the road???

Any info would be great. I love the car except for that damn noise. And when you get on it from a roll, I can almost feel the car torque and shift in the rear end. :(

SCANDINAVIAN13 12-06-2007 09:17 AM

You sure it's the frame mount? As in, the metalwork of the body is now cracked - not the shock mount itself?
If so:
The longer you wait to fix it and continue to drive on it, the more the upper suspension link will knock around in there, which will probably make it harder to repair.
I've heard repair quotes for that from $200-300. It should be taken care of. It's not going to kill you, but it's certainly not good for your car.

From your signature pic, your lights need to be adjusted as well. Specifically the passenger side. There are some DIYs online, or you can take it in for about $20.

tonyyank 12-06-2007 03:33 PM

That pic was taken in the summer, its all fixed now :)

I had some podunk mech look at it and all he said was "Your rear end is almost off the frame" I immediatly left. This is just a fun car, I own it. I beat it, and it blows in the snow. Just seeing if i HAVE to fix it, or it SHOULD be fixed. If i drop the clutch at about 3K its like BANG!!! If I ease off the clutch, its just sqeeks. I fixed one of the RSM already that took another noise away lol I wish I knew who had this car from new, cause they have absolutly NO respect for a BMW. Dumbass!!! Weekly and Monthly maint. on any vehicle is a must. My truck feels bad for my little bimmer :)

oakley 12-22-2007 01:39 PM

Can u look at the rsm's and see that they have failed? If so wot and where should i be looking and what for?? Thanks :)

SCANDINAVIAN13 12-22-2007 11:19 PM

If you have pictures, sure.
What you're looking for is a push through. Reach up in the wheel well and grab the suspension rod (the shiny, silver part) and move it up and down. If there is no push through, the silver part should not be able to move. If the RSM failed, it will be able to move due to a push through. Chances are, if you're on the stock RSMs it's going to happen at some point, so it's best to just upgrade and re-inforce now before something happens later. BavAuto is where I went for my parts to fix the problem with an upgraded mount and a reinforcement plate.

oakley 12-23-2007 02:15 AM

Marvelous I shall take a look later and see if I have any movements...Im getting a banging noise when reversing at almost full lock....

PhilipWOT 12-24-2007 06:54 AM

Good write-up, but you forgot one:
It sounds like an airplane engine taking off when I slow down- Worn out LSD. Time for a rebuild or new diff fluid.

SCANDINAVIAN13 12-24-2007 12:50 PM

Haven't experienced that one yet, otherwise it would've been in there.

zetorung 01-17-2008 09:32 PM

Rattling sound
 
I had a rattling sound from the rear passenger side suspension, so I put it up on jack stands and put it in gear. It was the brake pad on the inside of the rotor, one of the clips holding the pad had come loose and was giving "wiggle" room. Didn't hurt the rotor, just went and bought a set of pads for the rear and problem solved.

To give you an idea of what it sounded like, if you put a small bolt into a beer bottle and shook it around, it would sound very similar.

Jboss12 01-26-2008 08:42 PM

there is something that looks like a valve on my stock exhaust pipe, passenger side. e36 328i 1997. exhaust only comes out one of the pipes from the muffler. IS DIS NORMAL???

oakley 01-27-2008 08:44 AM

yup its normal..closes at low revs opens at higher...Unless u do the golf t trick and get a better sound...Just search Golf t

Jboss12 01-31-2008 12:02 PM

ok thanks. i'm not too worried about is cause im getting a new exhaust system soon. How's the Ansa Sport system for my car?

Jboss12 01-31-2008 12:02 PM

.

W4YNE-4 02-12-2008 03:04 PM

Airoplane!!!
 
HAVE TO SAY I AM EXPIERENCING THE AIROPLANE SOUND MENTIONED ABOVE ITS BEEN DOIN IT FOR BOUT A MONTH NOW AND FUNNY ENOUGH TODAY MY DIFF DECIDED TO SPRING A WEE OIL/FLUID LEAK, OH THE JOHYS WANTED A NEW DIFF ANY WAY BUT COULD HAVE WAITED ANOTHER COUPLE OF MONTHS:mad:

-Matt- 03-01-2008 03:09 PM

I have one to add...

When driving slowly and with the drivers window open I have been noticing a rattling noise, especially when going over any bumps in the road.

Turns out that the spring to close the fuel filler flap had become worn and the flap was rattling about. It can probably be fixed just by bending the old spring a bit and applying a squirt of WD40 - failing that the part (#51171888374) is listed on realOEM as costing $0.33!

BMWredneck 03-05-2008 11:26 PM

could someone make a thread on "Sounds from the Front: Explained"?


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