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audiophool audiophool is offline
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Default Motor mount failure = clunk on bumps? - 12-06-2019, 07:53 PM

As the title says^^

I put some B6 Bilsteins in my 535xi and immediately afterward I started getting a clunk over certain bumps. I went over the whole suspension with a fine tooth comb, and had the alignment tech check and he found nothing loose either. The bumps that aggravate the clunk are fairly shallow but long (if that makes sense) and aren't really speed-dependent. I don't hear any clunking on higher frequency bumps.

I checked the strut brace and a bunch of other things but everything is tight.

It occurred to me that if the mounts were going bad they might extend to their mechanical stops during certain g-loads on bumps where the mass of the engine works to overexend the mounts. The new shox are firmer than the worn out OE ones, so the clunks may not have been possible with those shox, hence first hearing after the B6.

You can hear it at about 1:31 on this clip: E60 clunk on certain bumps - YouTube



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Ripper61 Ripper61 is offline
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Default 12-09-2019, 12:15 PM

E60 535i, 110K miles. I started getting clunks/clanks over highway speed bumps at off-ramps and tollbooths. Soon after that came massive vibration at idle. I finally got tire of it and had both motor mounts replaced. Feel butter again.


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08 335Ci 08 335Ci is offline
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Default 12-09-2019, 05:59 PM

The old Chevy V-8's would let you know their motor mounts were bad by leaving you along side the road with a busted distributer cap.


No matter how fast I go there's always someone slower in front of me.

You can lead a horse to water but you can't make him Jet Ski.

'10 E92 335 M Sport, JB-4 G5 ISO, 3" CPE Charge pipe, WMI w/dual CM 5 nozzles, 3.5 Tmap, ARM Relocated Inlets (don't do it), VSRF Outlet, BEF, Front Strut Brace, SS brake lines, Drilled and Slotted Rotors, Anti-lag, OCC. Escort Max 360

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audiophool audiophool is offline
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Default 12-09-2019, 09:31 PM

Buddy's old '68 Dodge Polara let us know he'd broken an engine mount by tearing the hoses off the power steering and barfing fluid everywhere. The old school mounts had nothing to restrain their failure when the rubber let go.


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Default 12-10-2019, 10:23 AM

My 1985 325e would let me know by tearing the ground strap off the block, and also the alternator 'fan-pully' would cut through my coolant hose. Some strange issues for a kid to debug...




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chadillac2000 chadillac2000 is offline
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Default 12-10-2019, 10:51 AM

Considering you just put on a new suspension, I'd start there. I bet your motor mounts are fine. Double check that the end links on your sway bar are tight and that the top nut on the front struts are tight -- both will cause those type of noises.


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Default 12-10-2019, 11:37 AM

Quote:
Originally Posted by chadillac2000
Considering you just put on a new suspension, I'd start there. I bet your motor mounts are fine. Double check that the end links on your sway bar are tight and that the top nut on the front struts are tight -- both will cause those type of noises.

Nice work bringing this back on track.

Agreed. If mounts, and bumps make sounds, so likely would accell-engine brakes-acell-engine brake...




2008 335i Convertible, E93, N54, A/T (200,000+ km)
Wheels: 322 | Tires: R.275/35r18, F.245/40r18
TUNE: JB4/Trebila | 24 PSI | 100% Meth via dual CM5 | 94 Octane
BMS: JB4, Map 6 | WMI | 5" FMIC | OCC | DCI | Cowel Filters
RB: Inlets | PCV Valve
VRSF: DiPis | CP
HKS BOV
xHP Stage 3
NGK-97506 @ .020

Maintenance:
2018 - A/T Replaced | Ign Coils | Walnut Blast
2019 - Index 12 Injectors | VCG | OFHG & O-rings | TStat
2020 - OPG | Battery | IBS | Water Pump | Plugs | Alternator
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audiophool audiophool is offline
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Default 12-10-2019, 06:35 PM

Quote:
Originally Posted by chadillac2000
Considering you just put on a new suspension, I'd start there. I bet your motor mounts are fine. Double check that the end links on your sway bar are tight and that the top nut on the front struts are tight -- both will cause those type of noises.
I've been over it. Alignment shop has been over it. (Alignment shops are always happy to point out loose parts that might give them a chance to make you $$$pend more). There are no loose parts in the suspension. I know suspension noises, and this is not a suspension noise - way too dull and heavy.

I just picked a borescope - time to start looking for shiny spots on/around the mounts. Might get lucky and confirm the problem without tearing the 'skid' plate off.


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Default 12-11-2019, 09:57 PM

Hmmm, shiny spots. Maybe I'll rig the borescope and go for a drive.
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