On Tue, 6 Sep 2016 10:31:28 -0700 (PDT), wrote:

Yes it's normal to heat up, as the pistons are in motion they heat up as they are compressing air it generates a lot of heat! Notice the decals on the compressor stateing not to touch hot surface.

Golly Gee, life can be very interesting.

Put up a "Wet Paint" sign and watch people touch it.