Recently my dryer started making a clicking noise, similar to when the button of a pair of jeans rattles around in the drum. Problem was, it was only sheets in there. I thought I smelled something, and the clicking was getting more frequent, so I pulled the dryer out from the wall. The top portion of the back of the unit is discolored and was too hot to touch - especially for something that says it has a 0 clearance on the back side.

My first thought was the lint trap or exhaust tube, so I checked both. The exhaust runs right through the wall to the outside, so that's easy to check. The lint trap was good, so I pulled the front off the unit and found a rather large piece of flexible foam in the blower cage. I removed that and some built up lint and figured that would have fixed the problem. Got it all put back together, and the thing is still overheating (and putting out a LOT of air at the vent outside). I put my meat thermometer (all I had available) up against the back of the unit after about 5 minutes of running, and it hit 220 degrees. The clicking is definitely a click rather than a rattle - like a relay switching on and off. It's randomly timed.

There are 6 screws at the back of the drum, and I'm guessing I have to remove those to get to the heating element. I wasn't sure if the inner or outer ones would do the trick, and I could only get one of the six to turn anyway on my first attempt. Any thoughts?

Picture of discoloration attached. Somehow the drywall hasn't yet been scorched.

Thanks!

Thanks! Do I have to remove all 6 screws from the drum to get it out? Is it difficult to put it back in once it's loose?

I've got the front panel off, and the belt loosened and off the drum. I can't get the drum to budge though. Is there some kind of trick to get it out?

Ok, I tested both thermostats with my multimeter, and they're both reading .5 Ohms. The element is giving me 12. I don't know what else to check at this point. There's a piece of fiberglass-looking fabric right above the element (I'm guessing as a shield of sorts) and it's clearly scorched.

I had no idea how simple dryers were really. So few components. Either way, I don't know what else I could test. Could the thermostats show continuity even if they're faulty?

From the diagram, I couldn't identify the 'hi-limit thermostat'. I have small safety thermostat (attached directly to the cabinet-maybe the high limit?) and another one directly facing the heating coil.

You have probably done this but if not clean and check you vent system.

If you are using a plastic vent hose get rid of it. They hold lint and also if you do have a lint fire. The hose burns and often so does the house.
Best is proper round vent lengths and the proper elbows but the collapsible metal/foil are Ok but a pain to work with.