On Sat, 14 Dec 1996, Wiesner Craig wrote:

> I have had a high-pitched hum coming from my '86 syncro Westy for a few
> minutes most mornings, but it always went away before I could figure-out where
> is was coming from.  
(snip)  
> 
> Well this little cylinder is humming away and annoying as hell!  It doesn't
> seem to affect the engine performance, but when I was playing with it it idle
> change a little.
> 
> Question:  What is this thing?  Is it suppossed to hum?  Should I replace it?
> 
> 
>          - Craig
    It is a vacumme accuulator. Or called, a Vacumme amplifier. It may 
    have a leak in it, or dirt or a small amount of water, that will cause 
    this problem. The reason for this, is the axle Lock,  or anything that 
    needs more vacume than the engine can supply at one time. 

    My axle lock in my 2 wheel drive work fine without it!. 

                     Eric