Our 4 year old Maytag refrigerator (MTB2156GE) is not providing adequate cooling. We pulled it out and cleaned behind and below- all systems appear to be working, but even as we adjust thermostat for cooler temp, it remains tempid inside. Frig has also been making some loud noises- almost like the sound an empty plastic soda bottle makes when the air inside heats up and the plastic expands. Is there an online repair manual we can consult before calling in the expensive repair person?