What is the normal coolant temp?

[sifan]

I just installed an Autometer coolant temp gauge to my 2003 Toyota Echo with 46k miles and 50/50 Toyota long life coolant right after a radiator flush. The coolant temp will remain around 190F when the car is fully warm up and moving on a 65F day. When the car is idling in a stop-and-go traffic, the temp will reach 205F. If I turn on the heat and fan to the max, the temp will drop back to 180F. Is it normal for the coolant temp reaching over 200F since water boils at 212F?

What is the temp when the factory coolant temp gague reach the red zone that are found in most of the car and trucks?

 

[Drew99GT]

The cooling system is pressurized which significantly raises the boiling point. Depending on what psi the radiator cap opens all the way, coolent will boil in an automotive engine at around 265-270 degrees.

Most cars have a 195 degree thermostat, so yes, it is very normal to have coolent temps well above 200 degrees. I'd imagine your car has a 180 degree thermostat though. The cooling fans on my moms Olds 88 for example, don't even come on till 215 so it pretty much always runs over 200 degrees since it has a 195 thermostat.

 

[Matt_S]

This is not to mention that the ethylene glycol in the coolant raises the boiling point signficantly by itself. Between that and the pressurization of the cooling system, you should never boil the coolant.

Those temperatures sound completely normal.

 

[sifan]

Thanks for the reply. I have another question.

I also installed an Autometer oil temp gauge. I notice the oil temp will stay around 180F. Why is the oil temp lower than the coolant temp? Shouldn't they be the same since both come in contact with the engine?

 

[Matt_S]

Not necessarily. The coolant temp is thermostatically controlled and is responsible for extracting the leftover heat from the combustion process. The oil will absorb heat from friction as it lubricates bearings and surfaces and will absorb some heat from the block and head as it flows through passages. It will shed some of that heat when it returns to the sump, but is not thermostatically controlled in most engines. The temperature will depend on the air temp and engine load.

 

[sifan]

This will explain why the oil temp did not drop a bit but the coolant temp did as I turned on the heat and fan to the max.

 

[cousincletus]

Also, the temp sensor is in or near the head for the water temp. Water temp can vary a lot between the water entering and exiting the engine. For example, grab hold of your upper rad hose, then the lower. You can leave your hand on the lower hose all day long but not the top hose.

 

[unDummy]

Sounds normal.
But, if you have E-fans, verify that they are cycling correctly. And, thermostats don't last forever. To me, thermostats are overlooked maintenance items that should be changed more frequently.

 

[MN Driver]

The 205 degrees is nothing to worry about, some cars like the 2002 Grand Am that I used to own would crawl 20 degrees above that before the radiator fan would kick on and cool things down, it seemed pretty hot to me but it was a normal thing for that model. My Toyota on the other hand stays within a 10 degree range once its reached operating temp, unless it is well below freezing in which I have seen it steadily drop on idle with the cabin heat on full.

 

[mechtech]

Some new cars come with 205F thrmostats to increase the thermal efficiency of the engine.
Everything seems just fine, in your engine.

 

[SHOZ]

Sounds perfectly normal. You radiator cooling fan should come on at 210F or so.

The t-stat only sets minimum temperature, the radiator and radiator cooling fan will determine the upper temperature.