Temperature needle stays on the hot , have changed temperature sensor but it still stays on the hot and the engine is not overheating or leaking anything..what is making it stay on the hot

There could be a few different issues that could cause the temperature gauge on your 2008 Ford Focus to read hot when the engine is not actually overheating. Here are a few things to consider:

Failed thermostat: The thermostat is responsible for regulating the flow of coolant through the engine. If the thermostat is stuck in the closed position, it could cause the temperature gauge to read hot even though the engine is not overheating.

Failed temperature sensor: The temperature sensor sends a signal to the temperature gauge to indicate the engine's temperature. If the temperature sensor is faulty, it could cause the temperature gauge to read hot even though the engine is not overheating.

Wiring issue: If there is a problem with the wiring that connects the temperature sensor to the temperature gauge, it could cause the gauge to read hot even though the engine is not overheating.

To determine the cause of the issue, it may be necessary to perform some diagnostic tests and possibly replace some components. A mechanic or a professional auto repair shop will be able to diagnose the problem and recommend the appropriate repairs. It's also a good idea to keep an eye on the engine temperature and take note of any other symptoms or issues you may be experiencing. This information can help the mechanic diagnose the problem more accurately

you have overheated the engine maybe thermostat or water pump fault

most likely your thermostste is not opening. when you start the vehicle does it climb slowely or just shoot streight to hot on start up. if it goes to hot right off the bat you need to change the sensor that runs from the cluster pannel to the waterpump houseing

Actually, by your very description of the symptoms the car IS overheating. The temperature gauge should NEVER be "in the red" as this is too hot for the engine. The "puttering" you describe is the engine laboring to stay running in the overheated condition. This is shortening engine life dramatically. It sounds like you may have a thermostat that is not opening completely, or a cooling fan that is not operating correctly. If a fan problem it could be either the fan motor itself or the coolant temperature sensor that turns the fan on. It is imperative that you get this looked at IMMEDIATELY. The engine on your Cadillac has aluminum heads and they are easily warped or cracked by heat. A third problem you could have is a low coolant level. Never trust the sensors in the overflow bottles. If the coolant in the reservoir gets depleted, then the system develops air pockets which cause overheating and erratic gauge operation. If this is your problem, topping off the reservoir and purging the air in the system should clear things up. Be advised, however, you should also be on the lookout for system leaks if this occurs.

if engine over heating coolant over flow jug will boil over you will see steam.sound like you have either faulty engine coolant temperature sensor or could have faulty fans relay or fuse or pcm problem if coolant fans dont turn on.have garage with code scanner that can do a snap shot on coolant temperature sensor check see how hot coolant temperature is see if coolant temperature over 220 degrees engine getting too hot.could have faulty water or blowed head gasket check engine oil on oil dip stick look milkly you have blowed head gasket. i use infra red laser thermometor check see how hot engine is over 107 celsius engine is overheating.

a leak in coolant system will cause air pocket in the coolant system around the engine coolant temperature sensor.coolant sensor is a thermistor in which when hot cool cause it resistance decrease which affect the voltage from sensor to pcm which will cause engine coolant to turn on.if coolant level okay,check coolant fan fuse and relay, if all is good,engine coolant temperature sensor could be bad or have vechicle code scan for pcm problems it control the coolant fan.fill coolant system to correct level make sure engine coolat reservoir is at full cold mark and not empty.fill coolant system check for leaks,refill coolant overflow jug back to full cold mark dont over fill, if coolant overflow stay empty you have leak either its leaking or you have radiator hoses or radiator leaking coolant.when coolant overflow jug run dry it cause air get in coolant system causing overheating problems.

Does the engine appear to be overheating? Signs of engine overheating are :
1. Sluggish engine operation when hot.
2. Detonation upon acceleration (pinging).
3. Coolant boiling in overflow tank.
If any of these symptoms are present, then place a cooking thermometer on the upper radiator hose where it connects to the engine. Tape the thermometer to the hose to hold it in place. Run the engine until operating temperature is reached. The temperature should stay between approx. 195deg.F and 225deg.F. If it goes over 230deg.F, then overheating is indicated. Before shutting off the engine, check to see if the engine cooling fan is running. If not, then turn on the AC switch and see if it comes on. If the fan still does not turn on, then a faulty cooling fan or fan circuit is indicated. Other causes of hard/no start when hot include :
1. Dirty air filter.
2. Bad temperature sensor (computer).
3. Bad map sensor.
4. Bad EGR valve.
5. Failing ignition module.
6. Leaking injector(s)
If the vehicle is used primarily as a work vehicle, then it might be overdue for an oil change.
If the oil is fuel soaked, then it can cause an over rich mixture during hot restart.
I hope that this information is helpful and thank you for using Fixya.com.
CAUTION : Be careful when working around a running engine. Keep hands and loose clothing away from moving engine parts and engine cooling fan.

code po 1258 is an overheating code, need to check why u r overheating, start simple, do u have fluid, has it been changed , might need thermostat, how old is truck,. is there a leak anywhere.do pressure check on radiator and see if it leaks, check radiator temperature vs engine temperature. get a thermo scanner they work good. point and it reads how hot . if motor is hotter replace thermostat. check make sure oil level is good. get back to me let me know what u find..

u might have a sticky thermostat try takin it out and boil a pot of hot water and place it in if it stays closed or open and doesnt move it needs to be replaced