The primary function of your engine's thermostat is to maintain a minimum operating temperature in your vehicle's engine. When you start your engine cold, the antifreeze coolant mixture is kept within the engine by the thermostat. When the coolant temperature reaches the specified opening point of the thermostat, it opens. The lower temperature coolant will then flow through the radiator to keep the engine at a temperature close to the rated temperature of the thermostat. Most of the today's trucks are designed to operate at a particular operating temperature which is controlled by your thermostat.
If a lower temperature thermostat has been installed, it will affect several systems in your vehicle. A vehicle with a computer controlled fuel injection will sense the lower temperature and compensate by making the engine run richer, causing excessive fuel consumption and possibly a high idle. A lower temperature thermostat will also decrease the amount of heat available to keep you warm and defrost your windshield.
If your thermostat is stuck partially open or completely open, you will have the same symptoms as an incorrect thermostat. However, a thermostat that is stuck only slightly open will cause double trouble. A thermostat that is stuck open will delay engine warm up. It may also not allow enough coolant to flow at high speed to keep the motor cool and may cause an overheating condition.
If the thermostat fails, your car may overheat. If you run without a thermostat, the computer will always execute the motor to run in enrichment or warm up mode, meaning your fuel economy will decline, and your engine will produce less power.
A thermostat can last many years, but it might be a good idea to have it replaced the next time your cooling system is serviced as a preventive maintenance procedure. Replacing the thermostat is a relatively straightforward and inexpensive repair. To do proper preventative maintenance, most manufacturers recommend a cooling system flush and refill every few years. Please check your service manual for the proper cooling system intervals and service requirement for your vehicle.
Is your Cummins Diesel Engine starting to run hotter than normal? Over time the thermostat's spring will start to fatigue and not properly function at the correct operating temperatures. These are direct replacement thermostats that will simply bolt right in place for a quick fix.