Re: Help diagnose this @#$#%^@ E34 noise!

["Ron Buchalski" <rbuchals@xxxxxxxxxxx>]

>
>Date: Tue, 7 Dec 1999 22:09:17 -0800
>From: Jonathan Schwartz <jonathan@domain.elided>
>Subject: Help diagnose this @#$#%^@ E34 noise!
>
>Fellow BMW junkies:
>
>Over the past year or two, I've been living with the most annoying
>problem: A noise that I have not yet diagnosed.  I need expert help.
>
>Here's what I know:
>
>WHERE: The noise is coming from the engine compartment, driver side of my 
>e34
>
>WHAT: When it occurs, it lasts just a second in length.  It sounds
>like a small motor revving up and then back down again, with a low
>gutteral sound.  Kind of like an air gun, but 3 octaves lower.  I can
>feel the source of the noise as well, thru the gas pedal.
>
>WHEN:  It occurs nearly every time I start the car, back out and then
>take off.  It also occurs when a tire hits a pothole, and think that
>it is limited to the front passenger wheel.
>

Jonathan,

Does it always occur from a front wheel?

I have experienced a similar noise in my '93 525iT.  When the car is started 
in the morning, as I'm backing out of the driveway I'll hear a brief 
"whirring" noise, and feel a small vibration in the brake pedal at the same 
time.  I think that it's related to the ABS system, perhaps initializing the 
system.  It only happens the first time the brakes are used after starting 
the car.

I've also experienced it when hitting a bump, but only when I'm applying the 
brakes while hitting the bump.  And, in each case, I've been able to repeat 
it by going over the same bump and applying the brakes in the same manner.  
In my case, it's ABS kicking in on the one left front wheel which encounters 
the bump.  For one bump, it is a slightly depressed manhole cover.  If I'm 
braking for the stop light near this manhole, and the left front tire drops 
onto the manhole cover and experiences the slick surface of the manhole 
cover, the tire briefly locks up and ABS activates.  As soon as the tire is 
off the manhole cover, it stops.

In the other case, I was braking as I approached a stoplight, and 
encountered rippled asphalt.  The left front wheel encountering this ends up 
engaging ABS as it bounces over these ripples.

I'm beginning to suspect that the front shocks (or at least the left front 
shock) is showing signs of wear by not properly damping the motions of the 
wheel, and it only becomes obvious in these certain circumstances.  My car 
has 71k miles on it.

Does your car still have the original front shocks?  How many miles do you 
have on them?

- -rb

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