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#1
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SLK Rear Noise
Hi All,
I was driving in Baltimore today when a new noise developed in the rear of my SLK32. At 60MPH, the noise almost sounds like helicopter blades. The frequency varies with the speed of the car, and I can hear it going slowly as low as 20MPH. The noise ends when I mildly use the brakes or gas. I notice it very much when I am coasting. I also noticed that when I drive over painted lines, the noise disappears. I cannot tell if it is driver or passenger side. Any suggestions as to what to look for? Thanks!
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Black '03 SLK32 AMG |
#2
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First thing I would look for is ridging, cupping, bulges or indents in the tires. Either out of balance, or even possibly a broken belt within the tire can cause these sorts of noises. Then I would move on to the brakes looking for calipers that are not fully retracting and barely touching the Rotors.
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1983 300D-Turbo - Deep Blue w Palomino MB Tex (total loss in fire 1/5/09 RIP) 1995 E320 W124 Polar White/Grey Mushroom MB Tex 2005 F150 Supercrew - Arizona Beige - Lear topper 1985 Piaggio Vespa T5 - Black and Chrome www.cphilip.com |
#3
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I looked at the tires, and there's nothing obviously wrong. I have a tire-salesman friend look at it too though. I don't think it's the tires though because that noise would persist when I'm pushing the brakes or gas, because the anomaly in the tire would still impact the road.
I'll also check out the brakes today, but can you help me understand why the noise would end in the brakes if I accelerate slightly? Thanks.
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Black '03 SLK32 AMG |
#4
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Oh yeah, and the tire's are new. Only 3000 miles on em.
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Black '03 SLK32 AMG |
#5
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Any chance this could be related to a flex disc issue or maybe some sort of CV problem? (directed at everyone else not MGPep) I haven't heard the noise yet but by the sound of it he could have a flex disc/plate getting ready to go.
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E30 B25 126.036 123.130 with 616-Frankenbenz (sold) 124.030-Greyhound (sold) 124.030-Schnauzer (sold) DERP DERP |
#6
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When I was taking the wheel off to inspect the calipers, I found that three of the lug nuts holding on the driver side rear wheel were missing. I suppose they vibrated out. I replaced them and made sure they were ridiculously tight. The sound went away. Thanks for the help though.
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Black '03 SLK32 AMG |
#7
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Quote:
Nice to hear that the problem is identified and fixed.
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1996 E320 since 1/16/08, 171K miles as of Feb 2011 --------------------------------------------------------- 1989 300CE - R.I.P. Dec 29 2007 Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE |
#8
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#1 on list of tools to buy: torque wrench!
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1980 500SE/AMG Euro 1981 500SEL Euro 1982 380SEL 1983 300TD 1983 500SEC/AMG Euro 1984 500SEC 1984 300TD Euro 1986 190E 2.3-16 1986 190E 2.3 1987 300D 1997 C36 AMG 2003 C320T 4matic past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350 |
#9
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worst part is we used mine last time we had the wheel off... 80lbs iirc but we didn't retorque them which was probably the culprit.
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E30 B25 126.036 123.130 with 616-Frankenbenz (sold) 124.030-Greyhound (sold) 124.030-Schnauzer (sold) DERP DERP |
#10
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Quote:
I went on a road trip right after I tightened the bolts. I checked them after the trip (700ish miles), and they were looser again. Would over-tightening have loosened the threads or something so that the bolts are more easily vibrating loose? I can settle with tightening the bolts every 500 mile if I have to though...
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Black '03 SLK32 AMG |
#11
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I'd worry about cracked wheel bolts. Once you get movement like that, it's easy to fatigue the bolts. Below is an example of a wheel hub unit where the lugs were loose.
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#12
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Even if I've just replaced three of the lug nuts?
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Black '03 SLK32 AMG |
#13
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On Mercedes (and many other cars) the lug bolt is a separate piece that threads into the hub through the wheel, not like in the picture you posted, even if the original bolts were somehow fatigued the three replacements would not have been which makes that an unlikely problem. at mrgpep I would just check them once a week for now to make sure this is just an isolated incident, it is not uncommon to have to re tighten after that many miles but if you keep finding them loose every week or two then the hub may have stretched or stripped threads (which is pretty unlikely since the bolts themselves are designed to be weaker than the hub)
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E30 B25 126.036 123.130 with 616-Frankenbenz (sold) 124.030-Greyhound (sold) 124.030-Schnauzer (sold) DERP DERP |
#14
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The remaining two took up the slack in load. Plus there was movement. Every text book mentions that fastener fatigue can only happen when there is movement within the clamped assembly. With fatigue you get no deformation of the part, so there is no gross warning of the failure. Only a close inspection can tell you if the remaining wheel bolts have fatigue cracks.
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95 E320 Cabriolet, 159K |
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