If your antenna is making noise whenever you turn your radio on or off, then the motor is fine but the plastic track that drives the antenna mast up and down is broken. You can find replacement antenna masts on ebay - http://www.ebay.com/itm/Mitsubishi-MONTE...53d&vxp=mtr - you'll have to disassemble the antenna to remove the parts of the existing plastic track that are inside the antenna, but if you're pulling the fender liner to disconnect it, you may as well pull it out and fix it while you're there.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes