Thermostat Replacement Cost UK
A thermostat replacement at a UK independent garage typically costs £150 to £300. On older cars where the thermostat is a simple unit in an accessible housing, it can be as little as £90 to £150. Modern cars with integrated plastic housings and electronic map-controlled thermostats sit at the top of the range.
What it costs
The price spread comes down to design. An old-school wax thermostat is a £15 part under two bolts. Many modern engines use a complete plastic housing with the thermostat sealed inside, sometimes with a heating element and wiring, and the whole assembly gets replaced.
| Job | Typical price (independent) |
|---|---|
| Simple thermostat, easy access (older cars) | £90 to £150 |
| Integrated thermostat housing, plastic assembly | £150 to £250 |
| Electronic (map-controlled) thermostat | £200 to £300 |
| Coolant refill and bleed | usually included |
Symptoms
A thermostat fails in one of two directions. Stuck open, the engine takes ages to warm up, the heater blows lukewarm, fuel economy drops and the temperature gauge sits below normal. Stuck closed, the engine overheats quickly, often within a few miles. Many modern cars will also log a fault code and put the engine light on for a thermostat that opens too early, which is a very common MOT-season discovery.
Why it fails
The wax element inside a traditional thermostat wears out and stops responding accurately to temperature. On modern cars the bigger problem is the plastic housing itself, which goes brittle with heat cycles and starts leaking coolant at the seams or around the sensor. Electronic thermostats add a heater circuit that can fail electrically even when the mechanical part still works.
Can you drive with it?
Stuck open, you can drive, but you are wasting fuel, wearing the engine faster from running cold, and on many cars you will fail the MOT if the engine light is on for it. Stuck closed, no. Overheating a modern alloy engine even once can warp the head, and that repair costs ten times the thermostat. If the gauge climbs into the red, stop.
How to avoid overpaying
If the garage has the cooling system drained for any other job, a coolant leak, a radiator, a water pump, ask them to price the thermostat at the same time. The part is often the smallest cost of the job and the coolant drain and bleed labour is shared, so adding it while the system is open can cost £40 to £80 instead of £150 plus. Also ask whether the fault is the thermostat or just its temperature sensor, because on some cars a £25 sensor gets misdiagnosed as a £250 housing.
Common questions
How do I know if it is the thermostat or the water pump?
A thermostat problem usually shows as wrong temperature behaviour with no leak, either slow warm-up or fast overheating. A water pump problem usually shows as a coolant leak or noise at the front of the engine. A garage can confirm with a pressure test and live temperature data.
Can a faulty thermostat fail the MOT?
Not directly, but if it triggers the engine management light, that is an MOT fail on cars from 2003 onwards. A stuck-open thermostat is one of the most common causes of that light.
How long does a thermostat replacement take?
From under an hour on an easy older car to 2 or 3 hours where the housing is buried under the intake or other components, plus time to bleed the cooling system properly.