The thermostat is a valve that stays closed until the engine reaches operating temperature, then opens to let coolant flow to the radiator. Stuck closed, the engine overheats. Stuck open, it never warms up, your heat is weak and fuel economy suffers. AutoTech Clinic replaces thermostats at our Dearborn shop, usually the same day.
A thermostat is an inexpensive part that protects an expensive engine, and it is one of the first things we test when a car overheats or runs cold.
- How Long
- About 1 to 2 hours on most vehicles.
- Same Day
- Usually finished the same day.
- Vehicles
- Foreign and domestic, cars through trucks.
Signs You Need Thermostat Replacement
- The temperature gauge climbing quickly after startup
- The gauge sitting below normal and the heater blowing cool
- The engine taking a very long time to warm up in cold weather
- A check engine light with a coolant temperature or thermostat code
- The upper radiator hose staying cool while the engine runs hot
- Fuel economy that dropped in cold weather with no other change
What We Do
- 01
Watch Live Temperature Data
We monitor coolant temperature on the scan tool through warm up and watch where it stabilizes against the specification.
- 02
Feel the Hose Transition
A simple and reliable test: the upper radiator hose should stay cool until the thermostat opens, then get hot quickly. A hose that warms slowly from the start means a thermostat stuck open.
- 03
Check the Cause
Thermostats stick because of corrosion from old coolant or debris from a failing part. We look at the coolant condition so the new one does not stick too.
- 04
Replace With the Right Rating
Thermostats have a specific opening temperature for your engine. A colder thermostat does not help cooling and will set a check engine light.
- 05
Refill, Bleed and Verify
We bleed the system, bring the engine to full temperature, confirm the fan cycles and recheck the gauge and vent temperature.
Running Cold Costs You Money
A thermostat stuck open is less dramatic than one stuck closed, so people live with it. The engine never reaches its designed temperature, which means the computer keeps the fuel mixture richer than it needs to be, and your fuel economy drops noticeably.
It also means weak heat and a slow defrost, which in a Dearborn January is a genuine safety issue. The part is inexpensive and the job is usually quick.
Why We Check the Coolant Too
Thermostats stick because of corrosion and debris, and both come from coolant that has lost its additive package or from mixing incompatible coolant types.
If we find brown, rusty or sludgy coolant we will tell you, because fitting a new thermostat into a dirty system is a short term fix. A flush at the same time costs little and protects the repair.
What Affects the Cost
We quote your vehicle specifically after inspecting it, because these are the things that move the number up or down:
- Access, which ranges from a ten minute part to one buried under the intake
- Whether the thermostat comes as a complete housing assembly
- Coolant replacement at the same time
- Hoses and clamps that are brittle and should be replaced while open
- Vehicles with electronically controlled thermostats, which cost more
Call (313) 277-7200 with your year, make and model and we will tell you what to expect before you come in.
Why AutoTech Clinic
AAA Approved
An inspected facility that has to meet AAA standards for equipment and training.
Photos First
You see what we found and approve the price before anything is taken apart.
Same-Day Service
Parts on hand for the vehicles we see most, so you are not waiting on a delivery.