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FREQUENTLY Asked QUESTIONS - Thermostats

  • What is a thermostat? What purpose does it serve?
  • How does a thermostat work?
  • How often does a thermostat need to be changed?
  • When does a thermostat start to open?
  • When is a thermostat fully open?
  • Does Stant have a high flow thermostat?
  • Why does my engine overheat?
  • Why doesn't the passenger compartment in my car heat up?
  • Does Stant have a fail safe thermostat?
  • What does a jiggle pin do?
  • My thermostat has a jiggle pin but the Stant thermostat doesn't. Will a Stant thermostat still work?

What is a thermostat? What purpose does it serve?

The thermostat has two important jobs to perform; to accelerate engine warm-up and to regulate the engine's operating temperature. A quality thermostat ensures excellent fuel economy, reduces engine wear, diminishes emissions and blow-by, improves cold weather drivability, provides adequate heater output, and detours overheating. This is accomplished by blocking the circulation of coolant between the engine and radiator until the engine has reached its predetermined temperature. The thermostat then opens as required in response to changes in coolant temperature to keep the engine's temperature within the desired operating range. return to top

How does a thermostat work?

"Usually located within a metal or plastic housing where the upper radiator hose connects to the engine, most of today’s thermostats utilize the "reverse poppet" design, which opens against the flow of the coolant. Thermostats have a wax filled copper housing or cup called a "heat motor" that pushes the thermostat open against spring pressure.

As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within 3 or 4 degrees F. of the thermostat preset/rated temperature which is usually marked on the thermostat, the thermostat begins to unseat so coolant can start to circulate between the engine and radiator. It continues to open until engine cooling requirements are satisfied. It is fully open about 15-20 degrees above its rated temperature. If the temperature of the circulating coolant begins to drop, the wax element contracts, allowing spring tension to close the thermostat, thus decreasing coolant flow through the radiator. "

How often does a thermostat need to be changed?

Stant recommends the thermostat be changed when the coolant is changed or whenever an over-heating of the engine has occurred.

When does a thermostat start to open?

The thermostat starts to open at the rated temperature, plus or minus 2 degrees (F).

When is a thermostat fully open?

The thermostat is usually fully opened at 15 - 20 degrees (F) above the opening temperature.

Does Stant have a high flow thermostat?

Yes. Our Superstat™ thermostat has the highest flow of any thermostat available in the aftermarket.

Why does my engine overheat?

There are several possible reasons for an engine to overheat. Stant recommends that you start with the easiest to diagnose possible reasons at the top of the chart and work down until you find the solution(s) to your problem. Depending on your skill and experience level, it may be best to leave some of the diagnosis and repairs to a professional mechanic. CAUTION: Working on a hot engine can cause burns. Use extreme caution or allow the vehicle to cool completely prior to starting work on it.

Why doesn't the passenger compartment in my car heat up?

There are several possible causes for not getting heat in the passenger compartment of a car. Stant recommends that you use the chart below, starting at the top, where the problems are easier to diagnose and repair.

Does Stant have a fail safe thermostat?

All thermostats will fail in either a closed or open position; there is no such thing as a thermostat that will fail in a “safe” position. Although some brands may claim a thermostat fails in a safe position, it simply locks itself open while it is in a full stroke open position. It will not spring open if it fails in a closed position.

What does a jiggle pin do?

It helps bleed the cooling system of trapped air by allowing air to pass into the radiator and released from the system.

My thermostat has a jiggle pin but the Stant thermostat doesn't. Will a Stant thermostat still work?

Yes. Many thermostats have a “jiggle pin” that allows trapped air in the cooling system to pass through the thermostat and be released from the system. Some Stant thermostat do not use have a jiggle pin. These thermostats will have a "bleed notch” or other method of removing air from the system.