1988 Jaguar XJ40 3.6 Normal operating temperature

I have a 1988 Jaguar XJ40 with digi dash. If I go up a steep hill with the air con on and the external electric fan running the temperature will go up to 100 degrees Celsius. In normal conditions it runs at about 90 degrees Celcius but on hot days in South Australia it may go up to 95 degrees. Radiator, water pump thermostat all replaced and good. My question is 100 c to 105 c too hot for these engines or is this normal operating temperature.

Thanks for reading

'lo mate …

The first thing I would recommend is that you purchase a digital infrared thermometer laser temperature gun …

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These instruments are very accurate and amazingly inexpensive for what they do. With this you can read what the exact temperature is at various points around your engine and radiator. Remember the reading you get from the dash temperature gauge depends on the accuracy and condition of the engine sensor and wiring and also the calibration of the gauge itself, so plenty of room for error.

Running at 90-95C is perfectly normal. On a hot day with the engine under a heavy load even 3 bars above 90 (115C) wouldn’t really bother me if the temperature doesn’t stay there when you stop climbing that long hill.

Thanks Grooveman
I do have one of those Thermometers I use it to measure spark plug temperatures but that’s another story!

Yes the temperature does normalise once back to normal driving conditions so I won’t worry.

Just to give you an idea of what the dash marks represent on the digital temperature gauge …


Between 190 and 220 f is considered normal operating temperature range for the average car engine.
You’ll notice that the temperature gauge green bars don’t turn orange (warning) until 120 c (248 f),