It’s a 1989 Ford F-150 with 110,000 miles on it. 4.9L straight 6 engine. It’s a manual truck. It has had some issues with overheating. About 5 months ago started leaking coolant and over heating. Replaced the water pump (source of the leak), the thermostat, and the fan clutch (broke in the repair process). Since then, the temperature gauge inside the dashboard has not been reading properly but overheating seemed to have stopped from any other obvious signs. Fast forward a few month, truck was shipped from DE to CO and was fine for the most part(about a month). Recently replaced the oil pan gasket since. About a week after that it started running hot again. Replaced the Engine Coolant Temperature sensor and the temperature Sender to see if I could get an accurate temperature reading on the dash. The gauge moves a little more than it used to but still no accurate reading and the engine is still running hot. Not sure what else could help solve the gauge issue and the overheating issue.
Obviously the truck is over 30 years old. Your radiator could be clogged. As far as the gauge, carefully check the temperature gauge wiring. You could also check resistance of the new sending unit to make sure it's not defective. (There will be a specification in the shop manual.) It could be the gauge itself is bad. In that case the easiest thing to do might be to install an aftermarket temperature gauge.
If the radiator isn't clogged, get a new radiator cap and make sure all the air is properly bled out of the system.
