Why does an 1991 Mazda Miata's engine gage run hot but the does not over heat?

It is weared that the engine reads hot but never overheats. I live in central florida and with the air off it reads hot. The antifreeze is good the belts and hoses are new. The oil is good. Could it be because of the car being so old that the gage is just malfunctioning? Any mechanics out there that can help?Why does an 1991 Mazda Miata's engine gage run hot but the does not over heat?
All of the answers above can't be right *if* your motor truly isn't overheating.



What I think is happening (from personal experience since this happened to me) is that your alternator is overcharging your electrical system %26amp; battery.



Your temperature gauge is simply driven off voltage and resistance. The temperature sensor is simply a thermo-resistor. Changing temperatures in the coolant changes the resistance value in the sensor. The varying resistance allow a different voltage reading to reach the gauge (or the ECU circuit that controls the gauge) thus changing the display.



If the alternator voltage is 16 volts instead of 14 volts, the voltage into this circuit will read higher and this will show as a higher temperature on the gauge even if the temp isn't actually hotter.



Have your alternator checked for a bad voltage regulator.
Seems like you're running hot but not hot enough to blow the rad cap.

With an old car, the ability of the coolant to cool the engine can be reduced. Deposits can reduce the diameter of cooling lines and ports in the engine and in the rad. The cooling fins on the rad may be corroded off or plugged. These things can prevent enough cooling from taking place.

Other possiblilties are a thermostat stuck closed, you can take it out and test it in hot water easily, or coolant with too much glycol, not enough water, should be 50/50.Why does an 1991 Mazda Miata's engine gage run hot but the does not over heat?
Thermostat may need to be replaced. Could be Head gasket, radiator, Blockage or dirt somewhere....
To add to everything else-

The operating temp. of the engine is determined by several things-

Thermostat installed

Radiator cap used

Heat exchange capacity of the radiator

Fuel mixture

Timing

I don't worry about an engine running at the warm end of the scale. I have two 90 Miata's and they both run at 3/4 scale.

But when they start to run consistently hot I check my spark plugs. This can tell me if the engine is running lean. If it is the I replace the gas filter (even if it is not due), and run some systems cleaner through it. If this doesn't fix it then I would have the fuel system checked to make sure the fuel system is at the specified pressure. If it isn't it could be a stuck fuel pressure regulator, or a weak fuel pump.

There is also a temp sensor on the rear of the block that is used by the ECM to determine the fuel mixture to use. I replaced this on one of my Miata's (150K miles) because I had a leak in the area and could not see not replacing it while I had it out. The engine did cool off a bit after it was replaced and the idle speed came down. Can't say if it affected operating temp or not (but it did improve performance).

FYI, I replaced the fuel pump/s at about 100K. I have not had a failure of my pressure regulator/s yet. I would not suspect a timing problem unless the timing has been tweaked. I am assuming that the cam timing is right also. I have not had an injector problem yet either (150K miles).

A good systems flush would not hurt next time you replace the antifreeze either.Why does an 1991 Mazda Miata's engine gage run hot but the does not over heat?
meybe the sending unit