Brother-in-law ask me if I would put a thermostat 195* in his 98 F150. As it is not getting any heat, the temperature guage is in the normal range. I figured id help him out. Easy job, get it all done, run it to get it warmed up [17minutes], still no heat, it's a luke warm but no change from before, He also has a serpintine belt I put that on. No leaks top of the resorvoir. Noticed that the top rad hose isn't getting hot as usual as well as the heater hoses. Took the stat out check to see if it's opening fully or what, and did the hot water in pot test open right up water was at 197.6 digital meter, so that confirms the t-stat is good, now i'm thinking water pump but I would think the vehicle would overheat if that was the case but it is not, we made some dinner and let it idle for 1/2 hour temp guage normal, coolant full, top hose not hot, but warm. Scratch'in my head here. I'm gonna take the water pump off and look at it. I've never seen one for these engines, I'm a 78-96 bronco guru. But can fix anything. Are the pumps known to not last for this in these engines, It was replaced 9,000 miles ago as was the whole top end including the heads (stock). He fork a bunch of money to a idiot garage, only to take it back again for oil leak YIKES!. - Bob