Cooling System Components - Thermostats

Replacement Thermostats

What does a Thermostat do?

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 today's trucks are designed to operate at a particular operating temperature which is controlled by your thermostat.

What happens if you do not install the correct thermostat?

If a lower temperature thermostat has been installed, it will affect several systems in your vehicle. A vehicle with 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.

What happens if the thermostat is not functioning properly?

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. An open thermostat will cause the unrestricted flow of your engine's coolant to occur.

If the thermostat is stuck in the open position the following conditions will be present:

  • Your engine temperature will read lower than the normal range.
  • Your engine is not providing the same level of fuel economy.
  • Your vehicle's heating system does not produce heat.
  • The automatic transmission is sluggish when has shifting into higher gears
  • A thermostat that is stuck open will delays engine warm-up.
  • It may also not allow enough coolant to flow at high speed to keep the motor cool.
  • An open thermostat may also cause an overheating condition.

These are all byproducts of an engine that is running too cool. It results in all sorts of inefficiencies within your vehicle. While this situation may not be life-threatening to your car, your comfort and fuel bills will suffer until you get it fixed.

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.

If the thermostat is stuck in the closed position the following conditions will be present:

  • The flow of coolant used to remove heat from the engine is blocked and the movement of the coolant cannot reach your radiator.
  • The coolant temperature gauge goes it into the red
  • The temperature warning light comes on
  • Steam or smoke comes from under the hood
  • Your engine overheats.
  • Your head gasket fails.
  • Severe internal engine damage occurs.

Thermostat Replacement

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 requirements for your vehicle.

Is your engine is 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.

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