Calibrating temp guage

[taz]

Hi Folks,
Hoping someone can help..

I've calibrated my guage so that it reads in middle of the green at 82degC, which is the thermostat opening temp. And it reads in the middle of the red at 100degC. Under pressure, I'm assuming the cooling system should able to handle 110 or even 120degC.

Does this seem about right?

It seemed like a good way to setup the temp guage however after starting her up and letter her idle for 10-15mins, the temp was creeping up into the red (<90degC).

Not quite what I expected since I have a re-cored radiator, although it is only a 2 core job.

I may try a 71degC thermostat, but I was just wondering if anyone new what temp these engines idle at with the cooling system in good condition?

Cheers,
Taz.

Oh and I calibrated the guage by first measing the sensors resistance in an oven, then replaced the sensor on the car with a potentiometer to see how the guage behaved, then I used a resister in parallel with the sensor to 'tune' the guage to what I want. For info my guage read in the middle of the green at 56ohms, 37ohms gave the boundary between the red and the green, and 90ohms the boundary between the blue and the green.

[stantondavies]

These temperature gauges are not scientific instruments taz, and I would not expect any great degree of accuracy from them. I have always learnt what is normal for the car and check any deviation from that norm.
I would expect the system to operate at around the 90deg C mark. There is always going to be a differential in temperature with the cooling system, the thermostat will probably have a 10+degC spread between fully open and closed.

[Deleted]

Remember also that plain water boils at 100 deg C in open air, a closed system with a 15 lbs pressure cap will boil at a higher temperature.
Add the correct concentration of antifreeze and that also has an effect on the boiling point of water.

With the Coupes, the needle in the green sector is a happy place to be, in the red is not happy.

Cheers

[Phil Nottingham]

Unless there are other signs overhrating like rough idling and water loss I would recalibrate it to a lower temp! They are no where near accurate gauges or linear in their scales.

If the stat is working correctly it would not recommend fitting a lower version as undertemp is as bad as undercooling

[Smallfry]

71 degrees is too cold. The engine works more efficiently at around 85 degrees, also the oil does not self clean until this sort of temperature, so it will be degraded quickly and cause premature wear.

[taz]

Many thanks folks,
Very helpful as always.
Cheers,
Taz.

[p5tgc]

Just a comment to reinforce the comment that these gauges are indicators and not scientific instruments.
In a previous job with a major car manufacturer I recall there were many complaints from customers that their new top of the range cars ran with their temperature gauges frequently hitting the red segment. After some time the engineering fix was released, a new Gauge, exactly the same in all respects except it had no red segment. No more complaints!