Whether you're handling routine maintenance or diagnosing an overheating issue, replacing a thermostat is a straightforward but essential repair.
Note
Always check your owner’s manual for the thermostat’s location and the correct replacement part for your vehicle.
What to Expect
- Time Needed: 30-60 minutes
- Difficulty: Moderate
- Average Cost: $45
Source: 2025 Fleet Benchmark Report
What You’ll Need
New thermostat (check owner’s manual for correct type)
Gasket or sealant (if required)
Coolant (for refill)
Socket wrench set
Drain pan
Funnel
Shop rags & gloves
How to Replace a Vehicle Thermostat
Step 1: Drain the Coolant (If Needed)
- Park the vehicle on a level surface and allow the engine to cool.
- Place a drain pan under the radiator.
- Open the radiator drain plug or remove the lower radiator hose to drain enough coolant for thermostat access.
Step 2: Locate and Remove the Thermostat
- Follow the upper radiator hose to where it connects to the thermostat housing.
- Remove the bolts securing the thermostat housing and lift the cover.
- Take out the old thermostat and note its orientation.
Pro-tip
Some thermostats have a specific direction for coolant flow. Pay attention to this, as installing it backward can cause overheating.
Step 3: Install the New Thermostat
- Place the new thermostat in the same position as the old one.
- If required, apply a new gasket or sealant to the thermostat housing.
- Reinstall the housing cover and tighten the bolts evenly to prevent leaks.
Step 4: Refill Coolant & Bleed Air from the System
- Refill the radiator with coolant to the recommended level.
- Start the engine and let it idle with the radiator cap off to allow air bubbles to escape.
- Once the coolant level stabilizes, replace the radiator cap.
Step 5: Test for Proper Operation
- Monitor the temperature gauge to ensure it reaches normal operating range.
- Check for leaks around the thermostat housing.
- Take a short drive and confirm the heater is working properly.
Avoid These Common Mistakes
- Installing the thermostat backward. Most thermostats are directional. If installed incorrectly, coolant won’t flow properly, leading to overheating or poor heater performance.
- Not bleeding air from the cooling system. Trapped air can cause hot spots in the engine and lead to overheating. Always run the engine with the radiator cap off until air bubbles stop rising.
- Skipping the gasket replacement. If your thermostat requires a gasket, reusing the old one can lead to coolant leaks. Always replace it or apply sealant as specified.
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FAQs
How do I know if my thermostat is bad?
Signs include engine overheating, temperature gauge fluctuations, poor heater performance, or coolant leaks near the thermostat housing.
How often should I replace my thermostat?
Most thermostats last 50,000 to 100,000 miles, but if it sticks open or closed, replacement is needed immediately.
How much does it cost to replace a thermostat?
A DIY replacement costs $20 to $60, while a professional repair typically ranges from $150 to $400, depending on labor rates and vehicle type.
Can I drive with a bad thermostat?
It’s not recommended. A stuck open thermostat can cause poor fuel efficiency, while a stuck closed thermostat can lead to overheating and engine damage.
What type of coolant should I use after replacing my thermostat?
Use the manufacturer-recommended coolant listed in your owner’s manual. Mixing different coolant types can cause sludge buildup and reduce cooling efficiency.
