Engine temp is erratic

[Ericw]

Engine temp will rise and fall from 195 to 225 rather quickly in line 5 minutes, back and forth, any ideas ? I do get a antifreeze smell from the front of the truck , but can’t find any leaks

 

[Louhound88]

Engine temp will rise and fall from 195 to 225 rather quickly in line 5 minutes, back and forth, any ideas ? I do get a antifreeze smell from the front of the truck , but can’t find any leaks

Is this happening while parked? Or just while driving?

Thermostat should open at 195 I believe, but if you're driving and the engine temp is climbing to 225 then dropping to 195, then I'm not sure what that is. Once I get up to temp my truck runs around 220. Coolant temp is lower. But while just parked and idling i'm not near those temps. I'd say look at your thermostat to see if it is working.

 

[Rick3478]

Thermostat sticking or installed backward?

 

[SD Rebel]

It shouldn't be moving like that in 5 minutes. The normal range is 205F - 230F before the fans kick on. But should be stable, moving around 10 to 15 degrees in normal driving, but not 30F.

It could be a faulty thermostat.

 

[User_3336]

Driving, my coolant temp initially goes from 195 to 210. Then back to 195, then seems to stay around 203 (sweet spot).

Stop at a red light and I've seen it go to 225-230 WITHOUT the a/c on.
If the a/c is on, it stays at 203 and the electric fans come on, and the grille shutters are fully open.

After the red light turns, it still stays around 203.

 

[User_3336]

Is this happening while parked? Or just while driving?

Thermostat should open at 195 I believe, but if you're driving and the engine temp is climbing to 225 then dropping to 195, then I'm not sure what that is. Once I get up to temp my truck runs around 220. Coolant temp is lower. But while just parked and idling i'm not near those temps. I'd say look at your thermostat to see if it is working.

HUH? What is the 220, then?

 

[HSKR R/T]

Stock thermostat is a 203-205 degree thermostat. When first warning up, it's not unusual to get temp swings as the thermostat opens and closes before coolant in entire system is equalized and thermostat stays slightly open. When thermostat first open, you can see up to 210 engine temp, then the cold water from radiator hits the system, and drops temp quickly. Thermostat shuts again, fluid in radiator is cooled, engine warms back up, thermostat opens again, letting slightly warmer coolant from radiator into system, cooling engine back off, but not quite as much. Thermostat closes again, cycle repeats until coolant in radiator reaches the thermostat temp where thermostat stays slightly open allowing enough flow to keep engine cool, and radiator warm.

If sitting in park, the electric fans don't turn on until around 220 unless A/C is on. Then coolant will warm up until fans come in bringing cool air through radiator and cooling coolant back off until it reached around 210 when fans will shut off