I don't have a meat thermometer! How can you tell if a pork loin is done? (in a crock pot)
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The only way to be sure is to slice it through the center. Pork only needs to reach 144 degrees to kill its primary cause of food borne illness - the trichinosis worm. If the meat is slightly pink or white you are going to be way above that. Pork turns white at about 160 degrees.
I would let it rest for a few minutes before you slice it though, otherwise all of the juices are going to rush out through your cut.
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140 is just about the right temperature, and yes it should rest but slow cookers kind of take care of that. As far as trichinosis I don't think there has been a case more recently than the 1930's.