[s-cars] Loud rattling

[Tom Green]

The stethoscope tool is probably a good idea, JR.  Or, a long
screwdriver with the blunt, plastic end to the ear works for some
Otherwise, it's pretty difficult to diagnose a noise from this  
distance.  :-)

And, let's don't put this story out piecemeal, like Paul Harvey does  
his--
and now, the rest of the story....  :-)  The details are important,  
like the
brake light comes on.  These fluid levels need to observed regularly,
and it needs to be second nature to check them every time you open
the hood.  After all, it only takes a quick glance to know the status of
every level.   With that, I would suspect the noise is probably a  
cavitation
like noise of bubbles collapsing in the pump, caused by insufficient  
fluid
and probably  dirty filter/fluid and screens in the banjo bolts.   
Just a guess,
though.

I like that better that guessing metallic noise in the pump as it grinds
itself to small pieces.  This could come later if you run the pump  
without
it's source of lubrication and cooling.  You get the idea?

The belt tensioner is for the serpentine belt that runs all the  
accessories,
and is almost in front of the hydraulic pump.  It has a spring for  
tensioning
the belt that runs on the idler pulley.  You can observe the  
tensioner with
the engine running.  If it moves around a lot and imparts a jerky  
motion to
the serpentine belt, then that could be causing the random noise.   
You can
observe it for correlation with the noise.  I'm thinking tensioner  
spring here,
because of the random nature but it could be the bearing in the idler  
pulley.
There are other accessories on this belt that could be making noise  
without
any immediately noticeable effect on engine operation.  If the  
tensioner is
faulty,don't put off replacement for long, as failure can dispatch  
shrapnel
and belt parts around the front of the engine and radiator.

Tom




Previoulsy written:
> Date: Mon, 16 Oct 2006 12:21:21 -0500
> From: JR <audiurs4 at mailforce.net>
> Subject: Re: [s-cars] Loud rattling
> To: Steve Voit <stevevoit at comcast.net>
> Cc: s-car-list at audifans.com
> Message-ID: <4533BF91.8060109 at mailforce.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Forgive my ignorance, but where is the idler/belt tensioner.  Is it  
> the
> timing belt tensioner?  I replaced the whole thing last year.  I'll  
> have
> to buy one of those stethoscopes that just have a metal rod on the end
> to try to pinpoint where the noise is originating from.  What's got me
> is that the car runs great.  No excess smoke or smell and no oil
> spitting out of the tailpipe.  The engine sounds fine other than the
> rattling.  maybe rattle is a bad word.  It sounds like metallic  
> popcorn
> popping when it's almost done popping.  You know towards the end of  
> the
> 3 minutes in the microwave it pops randomly and only pops a couple of
> times a second.  It's like that.  The only other odd thing that has  
> been
> happening lately is that the brake light has been coming on when I hit
> bumps or turn sharply and staying on for a bit when it does come on.
> Could that be related in any way?  That might just be the fluid  
> levels.
> I'll check them when I leave for lunch.
>
> JR
>
> Steve Voit wrote:
>> Hi JR:
>>
>> I'd replace the idler/belt tensioner assy.  The bearings fail in  
>> these; some
>> have replaced the bearing, some replace the assy that includes the  
>> spring
>> and bracketry (I did).  It presents itself as you describe - random,
>> metallic, sometimes quiet.  When it makes noise it was startling  
>> in nature.
>> Mine, too, came on with the advent of cold weather.  My mechanic  
>> thought I
>> was nuts but it has cured the problem.
>>
>> Steve Voit 95.5 S6 Seattle