Another issue is many gauges read only coolant temperature
What a surprise I got after fitting the temperature gauge; the engine was running at 110 to 115 °C. Thinking the car has blown a cylinder-head gasket, we decided not to drive the car until we had the problem sorted. After a visit to the dealership, it was confirmed there was nothing wrong with the engine and a warning light should illuminate in the instrument cluster when the engine is overheating. Is this normal with a 50:50 water-andantifreeze mix and a radiator cap of 20 psi? What would the boiling point be in this case? SAM KRUGER Port Elizabeth We also value a temperature gauge in the instrument cluster rather than a warning light. We suppose many manufacturers believe that few motorists monitor this meter and maybe a red light draws more attention than an analogue gauge reading in the red.
There are a couple of problems with temperature gauges, though. The voltage signal from the temperature gauge drive and realise that something serious is wrong.
A better solution is a sensor that is installed to read the engine’s metal temperature close to a cooling jacket (usually in the cylinder head). When the coolant is lost, the metal temperature keeps rising and the gauge shows an overheating engine. Oil temperature is also a good indication of engine temperature and it should normally be around 100 °C (oil temperatures above 130 °C are on the hot side).
The boiling point of pure water at 20 psi (1,4 bar) is around 109 °C. A 50:50 coolant mix raises the boiling temperature by another 6 to 15 °C depending on the specific antifreeze used.
Therefore, we believe that it is very unlikely that the Sonic is running at the high temperatures you mentioned. We propose that you check the calibration of the sensor. An easy check is to measure the temperature of the water in a boiling kettle, as it should be close to 100 °C under standard atmospheric conditions.