Hino J05E 195 L4 5.0L

Hello all, I am new to the site looking on some insight on a Hino 195 and I hope I'm in the right forum. Full disclaimer this is the first Hino I've worked on, however I work at a dealer on larger equipment. Background on truck is a municipal garbage truck with lots of idle hours and 84k. Complaint when purchased was the truck would run all day and towards the end of the day, it would run hot. Before the city put it up for surplus Hino diagnosed it as it needed a head gasket but the city sold it before the work was done. We bought it, I put it in time, pulled the head, took to machine shop, $50 bucks later it checked out. Reassembled, new head gasket, by the service book new seals, torqued everything, and put in new thermostat. With the truck back together, I replenished coolant into reservoir, pressure tested, checked out. First test drive, got about 10 miles and sat at about half on the temp gauge. Shortly after the temp gauge went away for a second or two and came back peaked with CEL on. My main concern is the fan on the truck. I know the fan kicks on at a certain temp but it never kicked on. There are two identical plugs on the water pump housing. Could those be swapped? Is it just an air pocket? I know there is a lot of gray area but maybe someones had some issues like this. What are some things I can check?