Whether you can drive your car safely with a bad thermostat depends entirely on how the valve failed. A mechanic should inspect the vehicle before long-distance travel, as driving with a faulty thermostat can result in severe and expensive engine damage.
Cost for a car thermostat replacement is on average £150, with prices ranging from £95 to £215. Ultimately, the cost of replacing the thermostat depends on your car and what parts your car's manufacturer recommends using for the replacement.
When a car's thermostat goes bad, it usually gets stuck either completely closed or fully open. A closed thermostat traps heat, causing the engine to rapidly overheat and risk severe damage. An open thermostat lets coolant flow continuously, causing the engine to run too cold, decreasing fuel efficiency, and disabling cabin heating.
Disconnect the old thermostat and unscrew the mounting plate. Check the new thermostat instructions for compatibility and wiring guidance. Connect the labeled wires to the new thermostat. Attach the new mounting plate to the wall.
How can you tell if a thermostat is bad?
Replacement of thermostat unit
Upgrading to a new thermostat (unit + installation) typically runs $140 to $350, depending on model and complexity. There is also a broader range—$80 to $440—with variations based on location and type of thermostat.
A car thermostat typically lasts 10 years or about 100,000 miles. Often, they do not need to be replaced on a strict schedule and will function for the entire lifespan of the vehicle unless they become stuck, corroded, or leak.
A bad car thermostat usually gets stuck open or closed. Common symptoms include a temperature gauge that spikes or drops erratically, an overheating engine, weak cabin heat, poor fuel economy, or a lingering check engine light.
If the thermostat gets stuck in the closed position, coolant can't circulate through the engine, causing it to overheat. Engine overheating is serious and can lead to catastrophic damage, such as warped cylinder heads, blown head gaskets, or even engine failure.
Car thermostat replacement time is 30 to 60 minutes, depending on the make of the car. It will cost you around $190 to $350, including labor. Thermostat repairs usually take more time, requiring extra time to diagnose and analyze the vehicle's thermostat. It can take up to 2 hours.
Yes, a bad thermostat is a very common cause for a check engine light. The Engine Control Unit (ECU) constantly monitors the engine's temperature using coolant sensors. If the thermostat is stuck open or closed, the temperature will fall outside the normal operating range (usually 195°F to 220°F), triggering the light.
Upgrading your thermostat is a simple yet highly effective way to improve the efficiency of your HVAC system. A modern thermostat provides better control over your home's heating and cooling, resulting in increased comfort and energy savings.
If the thermostat is stuck shut it will not allow the coolant to circulate through the radiator. The engine will overheat and the water around the block may even boil, effectively meaning it is running dry. There will be a noticeable loss of power as it gets too hot and if the engine is left running it could seize.
One of the most common thermostat-related problems that homeowners run into involves incorrect temperature readings. A thermostat that displays incorrect temperature readings can cause significant heating issues. There are several potential causes of an incorrect temperature reading, starting with improper placement.
A bad T-stat can also force coolant out of radiator cap do to the higher coolant pressure than cap is rated for when over heated. You can also do a pressure test of the cooling system.
Check if the thermostat is stuck open.
The most basic test you can do is to start the engine on your car and allow it to idle for 10-20 minutes to reach its optimal running temperature. After several minutes, you will see that the temperature goes high while the engine is operating.
To verify if your car's coolant is circulating, perform a temperature check by comparing the heat of your upper and lower radiator hoses, or use the heater test. These checks require no special tools and only basic observation.
Mechanical Wear: Like any moving part, the thermostat can experience mechanical wear and tear, leading to reduced performance and reliability. Coolant Issues: Using the wrong type of coolant or neglecting regular coolant changes can lead to problems with the thermostat and other cooling system components.
A failing thermostat usually shows clear signs: the HVAC or engine behaves erratically, the screen is blank, or the temperature in your home/car does not match the settings.
A car thermostat typically lasts about 10 years or 100,000 miles. Rather than replacing it on a strict schedule, mechanics usually treat it as an "inspect-and-replace-as-needed" part. However, many professionals recommend replacing it proactively alongside major cooling system services, like a coolant flush.
Generally, repairing a thermostat costs around $200 to $500. This is the price range you'll find for most vehicles, although some may be higher or lower depending on the circumstances. But if we're talking complete replacement, expect the price to increase by $50.
A bad car thermostat usually fails by getting stuck open or closed. Key warning signs include a temperature gauge that spikes into the red (stuck closed) or stays near cold, poor cabin heating, fluctuating temperatures, or a "Check Engine" light.
Driving with a bad thermostat depends on how it failed: if stuck closed, only 5–10 minutes before severe overheating/engine damage. If stuck open, you can drive short distances to a repair shop, but it will run cold, hurt fuel efficiency, and potentially damage the catalytic converter over time.
Overheating is the most common symptom of a failing thermostat. Due to corrosion or aging, your car's thermostat can get stuck in a closed position. If this happens, the thermostat will not let the coolant reach the radiator, and, as mentioned above, the engine will overheat, causing severe damage.