QuestionI have a 86 F250 with a 460 in it. I noticed that when I would turn on the heater the temp guage would jump up then climb back down. I put a new thermostat in it and a new radiator. Now it is running all the way in the H. When I take temp readings at the sensor port on the manifold it is showing 246deg. Yet lower hose is around 150, upper around 180. Any ideas?
AnswerHello,
246 degrees Fahrenheit is not very hot. What device are you using to measure the temperature?
Does the vehicle over heat? (boil over, or push coolant into the return bottle) or does the gauge just rise?
If your temperature reading is accurate, I suspect a faulty temperature sending unit. It may also be wiring or dash / gauge unit, but they rarely fail.
Check the plug and wiring to the sender ( located on the left front corner of the intake manifold. that is driver's side of engine near distributor.)
You can usually replace these without too much fuss. Make sure engine is cool, and pressure has been relieved. I put the rad cap back on and have the new sending unit at ready with a bit of Teflon sealant applied to the threads. remove old sender and quickly install new one. You should have very little coolant loss.
If you would like to know how to test the sender, and have a DVOM, I can supply the test procedures.
