Proper engine operating temp Ford 4.0

[Bluestream]

My VW Beetle was not putting out much heat, hooked up the scan tool and was running 167 to 177F with Original thermostat. Installed a new Stant 190f Thermostat and now it runs 205f consistently.

Checked my Ford Explorer and it was running 185 to 190F with a 10 year old Motorcraft 190F thermostat. Should this not be higher? Internet Search shows general normal temps 195 to 220F

So what should it be and is 10 years about the lifespan of a thermostat?

 

[Lyman]

Anything under 210 is good. Ford gauges are not the best. I say this from my experience owning both Rangers and an Explorer. I always ran a 195 Thermostat

 

[George7941]

My Sierra has a 195F Stant Superstat in it and it runs at a constant 194F (90C according to the ScanGauge). With the original GM stat in it, it also always ran at 194F. So your Ford is running normally if you go by the behaviour of my Sierra.

 

[Falcon_LS]

190ºF - 195ºF minimum once the thermostat opens up.

220ºF is a bit high, albeit still "normal" as in it isn't overheating. Even in 130ºF ambient though, my 4.0L SOHC never hit 220ºF. The highest I've seen on my ScanGuage-II has been 213ºF.

 

[VeryNoisyPoet]

Thermostats can and do get lazy or drift out of spec with age without totally failing. My 8+ year old 194F thermostat was opening at 180F, causing weak heater when cruising and large temp swings when traffic slowed since the fans only kick on at 220F. Sounds like you're having the same symptoms on the Explorer, though not as severe.

Thermostats are cheap enough so swap it and see if things improve. Exercise the new unit in boiling water first to make sure it opens and closes properly. Good time for a cooling system flush too if you haven't done that in a while. Even my "clean" system spat out some grit when I flushed it, and that's after regular coolant changes its whole life.

 

[Oildudeny]

98 F150 with 4.2 V6 ran at 195

 

[SteveSRT8]

If you have electric fans they can account for temp changes. My old Silverado had twin units and only one failed, we would have never noticed except for the mild swing in temp when there used to be none.

At ten years I would check the stat and all other cooling system components carefully.

 

[Bluestream]

My concern is its running too cold for maximum engine efficiency and fuel economy. My VW fuel economy went up when the engine began running hotter.

Stant web site says thermostat only begins to open at stated degree temp, and is fully open at 20 degrees higher than rated. If thats the case then the explorer is definitely running too cold.

 

[SHOZ]

I changed both OE Hyundai t-stats last year because they were lazy. Ran at 180F, which is their opening rating. The new run at 187F. Fan comes on at 208F.