I think you can use thermocouple.

Approximately, how many degree you would measure?

Hi Hammam Hashfi Fadhlillah,

Temperatures around 400 to 450 degree would be fine. Are there any other instruments used apart from thermocouples? thanks.

Traditional thermocouples for on the road testing but thermal imaging is also used effectively in climatic chambers . We got useful models in combination with Simulation.

Ajeesh,

I admit, I have never had to instrument a vehicle engine.

But if I had to, I would:

a) Avoid thermocouples: small signal voltages are readily swamped by RF from spark plugs. J or K types would be most well-suited.

b) Favour thermistors: Cheap, simple to attach, and easy to interrogate.

c) Or even use Pt100 elements: Accurate, very wide temperature range, almost linear response.

For global measurements of the engine area I would probably hire an IR camera for a day or two to check for hot-spots or missing insulation.