Regulates coolant flow between the engine and radiator by opening and closing at a specific temperature, ensuring the engine operates at its optimal temperature for efficiency, emissions, and longevity.
$150 – $400
Total Cost
As needed (typically 80,000 – 150,000 miles)
Replace Interval
Moderate
DIY Difficulty
Fix Within a Week
If It Fails
The thermostat is a valve that regulates engine coolant flow. It stays closed when the engine is cold (allowing it to warm up quickly) and opens when the engine reaches operating temperature (allowing coolant to flow through the radiator).
Parts Cost
$15 – $80
Labor Cost
$100 – $250
Replace immediately if stuck closed (engine overheating). Replace within a week if stuck open (engine running cold). Proactively replace with any water pump or timing belt service.
German cars use electronically controlled thermostats that cost more but allow precise temperature management. Replacement is $200-$500.
VW/Audi thermostats are often integrated into the water pump housing. When the housing cracks, the thermostat is replaced along with it.
Honda thermostats are simple, reliable, and cheap — typically $15-$25 for the part. Easy DIY replacement on most models.