Vehicle doesn't reach normal operating temperature
Heat is only "luke" warm
Usually the car would run cool, unless the thermostat is stuck partially open.
Two easy ways to tell are if the motor takes too long to warm up. This means the thermostat may be stuck open. If the motor gets hot and the top hose on the radiator is not warm the thermostat may be stuck closed.
Thermostat is stuck open Thermostat is stuck open
thermostat can be stuck open
Overheating if stuck closed, no engine heat if stuck open.
To test a thermostat remove it while the motor is cold and make sure it is not stuck open. If it is stuck open when cold it is faulty. If it it is closed put it in water on a stove with a thermometer and heat the water. It should open at the temperature it is rated for wich is usually stamped on the thermostat. If it does not open when heated it is faulty. Thermostats are cheap and do need to be replaced occassionally; if I decide to remove a thermostat i generally replace it with a new one for piece of mind.
A thermostat can be stuck open or closed. If the engine runs to cool it is stuck open. If the engine is running hot it is stuck closed. If you don't have these problems you should'nt have to change it.
Stuck open thermostat.
Could be a stuck open thermostat.
If the engine is overheating, the thermostat is stuck closed. If the heater is not putting out enough hot air the thermostat is stuck open. Change the thermostat as a normal part of maintenance when changing coolant.
The thermostat is probably stuck open, even when the engine is cold.
Low coolant or stuck open thermostat.Low coolant or stuck open thermostat.