96 Ram 5.9 I changed the water pump, radiator thermostat, hoses.....fuel mileage dropped from around 15 to 10-12. Any idea what caused it? No codes showing so not sure if coolant sensor came unplugged. But that would show a code right?

 

Not necessarily....... The one you are interested in is cleverly concealed down by the thermostat housing. You know, behind/under the a/c compressor. (sorry man)

Check and make sure it is plugged in good.

Welcome to DF!

 

well we forgot the small bypass hose and the hose to the thermo stat is leaking a little so we are gonna check on that.