I have a 98 Chevy cavalier that say it's hot from the temperature gauge but its not running hot. I've replaced thermostat the water pump the heater core radiator cap hoses & it still says that its hot

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.

Why can't the shop that worked on it figure it out?

While it doesn't seem likely, if you've changed, or had the thermostat changed.... I'd say you got a faulty thermostat. I am curious as to what your temperature gauge says the temperature of the engine and coolant is.. If your gauge is showing hot, I can think of two more possibilities... the water pump isn't pumping right... and, if the water pump isn't working right, the problem can be a cracked head or block, which can cause an airlock in the coolant system. Check the coolant or radiator cap.

I'm not sure about the electric fan relay or fuse are but you may want to have your radiator flushed. It's possible that some of the tubes in it are plugged up and so your cooling efficiency could be low.

Change the coolant sending unit for the gauge. Usually this is different than the Coolant Temp. Sensor which is for the pcm. Maybe the sending unit is no longer functioning correctly after overheating. Of course, a scanner could show the temperature as recorded by the CTS, or you could use a hand held infrared temperature device to get a better idea of the true temperature.

It sounds like you have a plugged or clogged heater core. If the heater control valve was bad, both hoses would be hot, or cool.

my car still hot .we change the water pump,thermostat,coolant temperature sensor ,rad cap,and still hot the gauge is up and down??????

hello.....
first in this problem you need to look for cheapest things to do which is start with you thermostat abd make sure its open and close by how much temp inside the eng. then u need to feel the input hose and the output hose which they come from the heater core they should have closely same temp . if there is non of them have any heat thats mean the water pump blower is broke and u have to replace the water pump, if one of the heater core hose hot and the other cold the problem in the heater core , about the A/C light is on the A/C comprasser shoul work with the heat becuase hot air + cold air = dry air which u need for ur front DEF

Sounds like the water pump.Check if you see coolant or coolant residue behind the water pump pulley.

have you replaced the coolant tempeture sensor.