High Temperature Gauge

Reasons the Temperature Gauge Reads High

If the temperature gauge reads high, it could mean your engine is overheating. Another reason your reading might be high is you could be losing coolant. A small leak or evaporation may cause your radiator to slowly lose coolant. A third reason your temperature gauge reads high could be because the thermostat is broken. If this is the case, you may need a coolant temperature switch replacement. The last reason the temperature gauge could read high is because of a water pump, or water pump gasket failure. If the water pump is malfunctioning, it may need to be replaced by a professional.

What to Do If Your Temperature Gauge is High

If your temperature gauge is reading high, it means your car is overheating. This is a very serious matter and you should never drive an overheating car. If your car starts to overheat, shut off the air conditioner and open the windows immediately. If this does not reduce the overheating, turn on the heater as high as it can go. If this still doesn't work, pull over on the side of the road, turn off the engine, open the hood carefully, and wait until the vehicle cools down. Never open the radiator cap while the engine is hot - coolant can spray and burn you. Once the vehicle has cooled, take the car to a mechanic right away so they can diagnose the problem. Cars are especially susceptible to overheating in hot climates, like what's common in cities like Los Angeles, Phoenix, Las Vegas, or Atlanta.
The temperature gauge is an important tool in your vehicle that shows the temperature of your engine's coolant. Contact YourMechanic and have your car inspected for overheating if it reads too high, as this can cause serious problems...

Reasons the Temperature Gauge Reads Cold

On most vehicles, the temperature gauge reads cold until the engine has run for a few minutes. If the temperature gauge still reads cold after the engine has warmed up, the gauge may simply be broken. Another reason the temperature gauge could read cold is if the thermostat in the vehicle stays open. With the thermostat stuck open, the engine can be overcooled, causing a low temperature reading. If this is the case, the thermostat may need to be replaced.

have you tried to check overheat gauge?? some temperature sensor? isn't that faulty?? I don't mean thermostat, but sensor...

is it really overheating, or gauge is showing overheating???

long time ago I had car that had same problem.... never overheated, but still signalized high temperature.....that time it was temperature sensor probably not compatible with correct one ....

I guess that depends on what 3/4 is temperature-wise. Engines normally operate in the 180-210 degree F range depending on the thermostat and whether there is a mechanical or electric fan. Mechanical fans keep the temperature more stable. If you feel that after what you have done that the temperature indication is still too high, the issue may be with the sending unit for the temp gauge or the gauge itself. Have the coolant temperature checked with a second temp device if possible, otherwise, try the sending unit first and see what happens.

The gauge is supposed to move. Between 190 and 210 degrees. About a 1/16 to 1/4 inch movement with the needle. If it goes from middle(200 degrees) to hot(260 degrees) and back. Check the coolant level. Air pocket in the engine. Low fans come on at about 210 degrees. High fans come on at 225 degrees. High fans come on when the A/C is turned on. And it works.

you might have an air lock in the water system.
start the car leave the cap off put you bower on hot and leave for 10-15 mins if should get the air lock out

It could well be a faulty thermostat- test or replace same.
Could also be a blocked radiator core, - check coolant or airflow is not restricted,
Ensure any radiator leaks are repaired,
Ensure coolant level is correct, without airlocks - bleed as necessary on re-fill,
Check operation of cooling fan - ensure fan runs at appropriate engine temperature - if not check sensor switch and associated relay operation.
Thermostat is located at the end of top radiator hose where it connects to engine housing.

Yes, it is possible the temp. sender is faulty, but I would do a cross check of the actual coolant temperature vs gauge reading using a cooking thermometer in the top of the radiator.
Take care not to get scalded - check it at about 180 to 200 deg.

It could be 3 things: Temp sensor, thermostat, or fan relay. Fans don't usually turn on until car has been idleing for a while. I first would change thermostat, then relay, then temp sensor. Coolant must be 50/50 mixture for water pump to have proper lubricant from antifreezer. Do not go any further than a 60water/40antifreeze mix

Sounds like you have installed a 'over-temperature switch' type sender unit- this type of sensor is only meant to control an over-temperature alarm indicator lamp that is either 'on' or 'off'.

The temperature gauge requires a 'variable resistance type' temperarure sensor to control the meter deflection.
When cold the temperature sensor is of high resistance, hence less meter deflection;
when hot temperature sensor is of low resistance, hence more meter deflection.

You need to procure a matching sensor to suit the type of gauge installed.

Is it possible you have connected to the temperature wrong temperature sensor? - most vehicles are fitted with both a gauge type (variable resistance) sensor to drive the temperature gauge, as well as a switch type (on or off) sensor to drive the overtemp indicator light.

how is the radiator and the thermostat?  Do the cooling fans come on?  Are you totally filling the cooling system and bleeding it?