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-   -   occasional strange clunk noise (http://www.maxbimmer.com/forums/showthread.php?t=145991)

ng78 09-26-2011 06:22 PM

occasional strange clunk noise
 
I'm just wondering if somebody out there has any idea of what this could be. About 5 or 6 times now, I'm driving along, at a low speed in traffic, and I get a loud clunk, feeling as though I've run something over, or perhaps some heavy metal object has fallen from the car. In all cases, when I look at the rear view mirror, or when I've been able to stop, there's no indication of anything at all, and the car continues to drive normally.

Sorry, but this is the best that I can describe - any ideas?

ng78 09-26-2011 06:22 PM

sorry - the car is a 1991 BMW 318iS

E36is 09-26-2011 06:25 PM

couple of things:

motor mounts
front strut bearing, RTABs
guibo
how tight are your wheel lugs? torque spec'd?

ng78 09-26-2011 06:28 PM

Motor mounts, wheel bearings, etc perhaps. When I'm back in Toronto I'll check the wheel lugs, but I don't think that might be it. The car drives tightly and doesn't show any signs of wheel or suspension issues.

I've had this car as a toy for 5 years or so and it's never let me down. Now that I have a car in Montreal for work and the BMW in Toronto when I'm in town, it's starting to be finicky lol.

Thanks for the reply!

Ceeker 09-26-2011 08:55 PM

usually, this is a motor mount issue. Get your friend to put the car in 1st gear with the clutch in. Stand on the break -make sure you also have a wheels chalked for safety under the front wheel. See if the motor moves DRASTICALLY when he's on the gas and backs off. If the motor rocks back and forth then you have a bad mount(s).

wheel bearings usually droan under load when turning.

Strut bearings usually clunk similar to CAB and can make noise while driving over bumps.

Trailing arm bushing don't clunk - they usually make the car unstable in the rear when driving aggressively changing lanes or cornering - giving a stepping out feeling of the back end. if anything it would be the rear sub frame bushings. This would also cause a clunking sound again when off and on the gas-under load.

check guibo as suggested and transmission mounts as well and "maybe" a bad u-joint but that would need to be pretty severe.

ng78 09-26-2011 11:04 PM

Thanks Ceeker. I'm leaning towards a motor mount based on yours and E36is' response. Hopefully I can get that checked out soon!

everlast 09-27-2011 12:22 AM

I vote rear sub frame, but motor mount could be too. Usually when they're broken you can visually see they've been severed in half. :D

ng78 09-27-2011 12:43 AM

The strange part of this is that it's very occasional, happening only a few times in the last couple thousand km's or so, and always in light acceleration at lower speeds it seems.

If this car starts costing me too much money, there might be a very clean E30 on the market soon :P

MaxBell 09-27-2011 08:00 AM

Mine did this and it was the centre support bearing. THe driveshaft was knocking under higher torque every one in a while.

The Twin 09-27-2011 08:57 AM

if the sound is comming from the back, don't rule out e-brake BS.

once it goes it creates a virtual symphony of metal/metal grinding and squealing.

ng78 09-27-2011 10:40 AM

Quote:

Originally Posted by The Twin (Post 1525862)
if the sound is comming from the back, don't rule out e-brake BS.

once it goes it creates a virtual symphony of metal/metal grinding and squealing.

Good point. I took the car to Bavarian Motors for the first time for an oil change and a quick overview. I never mentioned this particular clunking noise as it hadn't happened in a while, but they did say that the backing plates for the e-brakes were worn, and they will be replaced next time I'm in town.

E36is 09-28-2011 05:56 AM

^^ if the e-brake support bolt broke free you would constanting hear a clicking sound. Mine broke free and i thought the diff went because of all the grinding and clanking in the back (constant noise). $5.00 and a trip to homedepot cured that mess.

Ceeker 09-28-2011 07:54 AM

Quote:

Originally Posted by ng78 (Post 1525875)
Good point. I took the car to Bavarian Motors for the first time for an oil change and a quick overview. I never mentioned this particular clunking noise as it hadn't happened in a while, but they did say that the backing plates for the e-brakes were worn, and they will be replaced next time I'm in town.

Are you prepared for an expense when time comes to remove the backing plates? if they do it correctly, you'll need to remove the bearing to remove the backing plate. or they may cut and tack weld one back on. As mentioned a simple fix for this are a couple bolts and nuts and you're back in biz.

ng78 09-28-2011 10:43 AM

Quote:

Originally Posted by Ceeker (Post 1526052)
Are you prepared for an expense when time comes to remove the backing plates? if they do it correctly, you'll need to remove the bearing to remove the backing plate. or they may cut and tack weld one back on. As mentioned a simple fix for this are a couple bolts and nuts and you're back in biz.

Well, problem is I don't know enough about this and can only go on theirs or other mechanic's advice. I'd rather do it correctly, than a quick fix that will not permanently solve the problem. Unfortunately I'm not well versed enough to make that call in this case.

Right now it will cost me $650 or so.


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