I have a Scotsman ice maker that is making a ton of noise... I've vacuumed out the coils and snooped around under the cover. The fan that cools the coils is loose but there is no way I can get to it to tighten it up (too crammed in there)...

Any ideas??

What size and model number? If the condenser fan motor is loose and not turning properly, this will cause your head pressure to be to high in your refrigeration system. Sometimes you also need to blow out the condenser coils because a vacuum won't suck the dirt out of the condenser. Try to shine a flashlight through the coil, you should see the light at the other side of the coil. Having a clean condenser with the proper air flow is extremely important or your ice machine will fail.

Jack...
It's a Scotsman DCE33 (Scotsman United States - Oops!. I'll try blowing it out. It's not that the fan isn't working... When I turn it off and feel around with my fingers, the fan appears to be slightly loose and is causing the loud rattle at full speed. I'm sure it's because I haven't kept the coils free of dust (only cleaned it twice in 7 years)... But even spotless clean, I fear it's still going to rattle loudly until I get that fan tightened up? Agree? Disagree?

Sometimes the hub on the fan blades start to split and crack and it will have to be replaced with a new one. You can download service manuals at Scotsmans web page.
Scotsman United States - Manual Downloads

Hope this helps.