Thermostat Replacement Service and Repair

Engine Thermostat Diagram and Operation

Thermostat Replacement Service and Repair

Thermostat Replacement Service and Repair

What is a Thermostat and what does it do?

A thermostat is a heat-controlled valve used in the cooling system of your car to regulate the flow of coolant between the engine and radiator. An additional thermostat may also be used in the cooling system for an electrical control circuit of the car’s climate control system to control the amount of heat supplied to the passenger compartment. The valve of the thermostat is designed to be completely open above a certain minimum temperature. On most vehicles, it about 190 degrees Fahrenheit. Some cars have a thermostat for regulating coolant through the oil cooler for the Automatic Transmission which may or may not be part of the Radiator Assembly. By regulating the amount of cooled coolant re-entering the engine from the radiator, it is possible to maintain the engine at optimum operating temperature.

What are Common Symptoms Indicate that you may need to replace the Thermostat.

  • Engine Overheats
  • Check Engine Light
  • Loss of coolant due to pressure relief of radiator cap due to overheating
  • Engine always runs colder than normal.
  • Heater does not blow hot air or get warm
  • Engine Runs Rough by running too cool or hot consistently


How important is a Thermostat Service or Repair

It is never good to have an over-heating engine. Delaying replacement of the engine thermostat and continuing to drive the car can only result in far more costly engine repairs or replacement. We strongly encourage you to stop driving your vehicle and have it towed to a quality repair shop. Many modern engine thermostats contain a sensor for the computer to determine if the thermostat is operating properly. Many modern cars have also eliminated coolant temperature gauge.  If your car gives you any warning indicators or check engine light related to your cooling system, get it checked immediately. Modern cars that don’t have a coolant temperature gauge in the dash are programmed to shut down the car’s engine when extreme over heating is detected and can often do so without much advanced warning. Typically, when such a situation occurs, severe and expensive damage has already occurred. Most motor oils need to be at least 175 degrees Fahrenheit to properly lubricate internal engine components. Continuing to drive a car with a thermostat that is always stuck fully open and allowing the engine to always run cooler than normal will result in extensive internal engine wear and damage.

General Repair or Service Procedure (NATEF Standards):

  • Pressure Test and inspect cooling system for leaks.
  • Check Codes and Data. Perform related actuator tests, if possible.
  • Replace Thermostat
  • Remove and replace water pump if failed
  • Fill with new coolant and bleed system
  • Install new Reservoir or Radiator Cap
  • Clear related engine codes
  • Test Drive car and review engine data


Additional parts and labor that may be needed:

Depending on the engine design additional parts and labor may be required

  • Replacement of the Water Pump should always be recommended with Thermostat Replacement.
  • Water pumps driven by timing belts will require timing belt, belt tensioner, and idler pulley replacement.
  • Drive belts may need replacement.
  • New Coolant (water) hoses may be needed
  • Vehicles with electric or computer controlled thermostats and coolant pumps will need to have computer initialization and adaptations reset


Preventative Maintenance Recommendations:

Have your coolant system flushed with new coolant every 4 years or 40,000 miles. This will insure proper ph balance of the coolant and prevent internal corrosion of components and extend their life. Always use manufacturer OEM or recommended Coolant (Antifreeze). It is no longer ok to use green coolant for general replacement. Exotic metals and materials in modern motors require special chemicals to preserve their operational life, which can only be provided by the proper OEM coolant.


Sprint Motorsports takes pride in caring for our customers, and we are invigorated by the opportunity to provide competent and comprehensive automotive repair services. We are the leading auto repair, tuning, car service, automotive performance shop in San Jose and adjacent areas while providing you personalized, detailed, and friendly service. Our relationships are built on trust, communication, integrity, and commitment to our purpose; to be the best auto repair shop we can be.


We stand behind our work with a 2 year warranty on repair work!!!*

To schedule an appointment for a Thermostat check and replacement, or other car repair, major or minor services, please contact service@sprint-motorsports.com or 408-831-3730. We welcome you to stop by our auto repair shop located at 2099 S 10th Street, Unit 40, San Jose, Ca 95112.  If you have any questions about your car’s repair needs, performance, or maintenance, ask our friendly and expert staff for assistance.