Mystery Noise

[Jonathan Schwartz <jbschwartz@xxxxxxxxxxxxx>]

 Thank's for the help last week with the under-the-seat vented battery=
 search.  Problem solved.

This week's challenge is to figure out exactly what is malfunctioning under=
 the hood that I believe is tied to the anti-lock braking system.  Nearly=
 every time I start the car and back up out of a parking space, driveway,=
 etc., I hear a short burst of sound from under the hood, together with a=
 vibration.  Perhaps it is coming from the front driver side.  The closest I=
 can come to describe it is the sound of someone pulling the trigger once on=
 an airgun, but a much lower octave.  (Brrrrrr!)  It usually occurs I take=
 my foot OFF the brake pedal (we've just backing up at 1mph).

I theorize that it is the antilock braking system malfunctioning in some=
 way.  Perhaps there's a hydraulic pump associated with the system that=
 kicks in to activate the brake cylinders. If there was such a pump that=
 turns on instantaenously...that would probably be it.  The brakes don't=
 actually lock up or get applied by the system when this happens.  I'm=
 thinking that somehow the system is starting up, then quit immediately...pe=
rhaps a bad sensor.

I've asked both the dealer plus my trusted mechanic..who both says thare=
 there  is no such pump.  I would get a code if the system malfunctioned. =
 They just scratched their head. So much for their help.  After a year of=
 this, I'm tackling the problem myself.

Unfortunately, it's really hard to tell what is making the noise while=
 backing up.

Any suggestions?

Thanks in advance.

Jonathan Schwartz

- ---------------------------- * * ----------------------------
Jonathan Schwartz, Software Licensing/Business Development
Schwartz & Company
ph (415) 381-1852      fax (415) 381-1855
817 Marin Drive Mill Valley  CA 94941    jbschwartz@domain.elided

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