Distributor rattling

Phil Rose pjrose at frontiernet.net
Tue Jan 27 16:01:00 EST 2004

At 8:29 AM -0800 1/27/04, Bernie Benz wrote:
>  > From: Phil Rose <pjrose at frontiernet.net>
>>  At 7:01 AM -0800 1/27/04, Bernie Benz wrote:
>>>  Bentley says tight enough that you can just twist its longest 
>>>span 1/4 turn.
>>>  This is not quite tight enough, IMO.
>>  I'll assume that you have "cured" (one or more) distributor rattle
>>  situations by retightening the timing belt to just beyond that "1/4
>>  turn" spec?
>Phil, you are introducing confusion into my belt tightness opinion!

Heaven forfend!

>   Not "just beyond", but less than 1/4 turn would be correct.

Yes, to avoid confusing the easily confused, I ought to have said 
retightening so as to permit _less_ than a 1/4 turn twist.

>I have never experienced the "distributor rattle" syndrome on either my 3B
>nor 7A, always running tight belts so, No, I have never cured a nonexistent

I wasn't expecting that you would have cured "a nonexistent 
problem"--just wondering if the _quantitative_ aspect of your 
"theory" (tighten somewhat beyond the 1/4-turn spec) was based on any 
BTDTexperiences.  I don't disagree with the belt-looseness 
theory--only question if there's any basis to assert that the  "1/4 
turn" (as opposed to 1/5 or 1/6) spec inherently fails to produce a 
properly tightened t-belt. It's just as easy to blame some weak 
fingers. Old Karl, the 300-lb Monkey Lad,, might bring the belt to 
much a different degree of tension (before reaching the same 
"1/4-turn" spec.) than does his new assistant, Gertrude (the 100-lb 
Monkey-Lass). So is the spec at fault? Well _yes_, but not because it 
needs to be changed to 1/5 turn instead of 1/4 turn. It needs to be 
something less subjective--especially for the DIY mechanic.  I 
suspect that the typical mechanic, wishing to avoid the rattle 
problem, might simply go much, much tighter than the 1/4-turn spec. 
But I've assumed that "overtightening" could have negative effects 
(i.e., excessive wear of bearings/bushings). Is this not the case 
with t-belts?

Anyway, in my previous post I described a beneficial effect (i.e., 
reduced rattling) after i installed a new belt which I adjusted to be 
tighter than the old belt had been (but still not more than the 
1/4-turn "spec"). So you respond with the opinion that in _my_ case 
the tighter belt must've had nothing to do with reducing distributor 
rattle (see last line, quoted below). Well, Bernie, were you just 
joking, or are you asserting that anyone who tightens the t-belt to 
the 1/4 turn spec will definitely have a  belt that is too loose?? 

>  > Of course the basic problem with Audi's (and most other)
>>  belt-tightening specs, is the lack of an objective means to establish
>>  the force--torque in this case--to be used. Over time...and many
>>  t-belt jobs...one presumably gets the required "feel" for belt
>  > tension, but otherwise...it's a pretty darn vague kind of spec.

>Also, there those DIYers among us insecure enough that they must use an
>uncalibrated torque wrench on every nut and bolt.

  Oh, dear me, I guess your point is that I'm too "insecure" to 
believe my (1/X-turn) finger-twisting will necessarily result in 
optimum belt tightness?? Yep, guilty as charged. We don't all have 
those calibrated fingertips, Bernie...

>  >
>>  Ingolstadt's assembly line possibly has a specialist (Karl, the
>>  300-lb Monkey Lad)  who does nothing all day but twist timing belts.
>>  ;-)
>>  Phil
>>  P.S. I used my own personal version of that  "1/4 turn spec" for the
>>  t-belt I replaced on the red car, last year; and there's been no
>>  significant distributor rattle. However it did rattle a lot before
>  > the belt change, and the old belt did seem quite loose.

>IMO, had nothing to do with the belt change.

I'd like to hear your "rationale" for that opinion.


Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net

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