TACO circulator pump running constantly
Our two year old TACO cartridge cirulator pump is running constantly and now very hot (moreso than the supply pipes) - probably been running that way for a couple weeks, at least. It's making a louder than normal sound as it runs, almost like sandy water/grinding noise.
While the boiler (Hydrotherm with 85,000 btu input) is old, it was moved and fully serviced two years ago, getting two zones (one for radiators upstairs, and one baseboard loop in basement, new TACO cartridge pump (#007-F5), Honeywell zone valves, new expansion tank, PRV, new feed shut-off valve etc.
The house is two story (and basement), and boiler pressure is 12 PSI (seems low, right?), yet the feed is open.
I've got service scheduled for two days from now. I do need heat, but wondering if I need to shut off the heat periodically, including the furnace circuit to give it a rest.
Also, any idea what the problem could be?