Posted by Bill Bethia on December 31, 1999 at 17:11:41:

I have a Crane boiler from the mid to late 70's and have replaced the pump and ignition coil
lately. I have also installed a spiral vent in the last year. The boiler ran and sounded fine after
these changes, until recently. It has began making a "shh shh shh shh" noise that sounds
kind of like a train starting to move. The pressure bounces from 12 to 20 psi in unison with
the noise. I have drained the system to check for blockage with no effect on the problem. I
have noticed that if I close the valve to the expanssion tank the noise stops immediatly.
However presure builds and I have to open the valve. This is the only thing I have found that
effects the noise. Raising and lowering base pressure have no effect, nor does closing
leggs of the system. The noice definatly comes from the boiler unit itself, not the pump or
pipes. Anyone got any thoughts???

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