🔧 Thermostat - Replacement

The thermostat controls engine coolant flow so your CX-5 can warm up correctly and stay at the right temperature. If it is stuck open or closed, you can get poor heat, overheating, or a check engine light.

Difficulty Level: Intermediate | Estimated Time: 2-3 hours

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⚠️ Safety & Precautions

• Work only on a completely cold engine. Hot coolant can cause serious burns.
• Use eye protection and gloves. Coolant splashes are irritating and slippery.
• Coolant is toxic to people and animals. Catch it in a drain pan and clean spills right away.
• Do not open the radiator cap on a hot engine.
• Battery disconnect is not required for this repair.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• Ratchet
• Short extension
• Drain pan
• Flat-blade screwdriver
• Pliers
• Torque wrench
• Funnel
• Safety glasses
• Gloves
• Jack stands
• Floor jack (rated 3-ton minimum)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Thermostat - Qty: 1
• Thermostat housing gasket or seal - Qty: 1
• Engine coolant (Mazda FL-22 equivalent) - Qty: 1-2 gallons
• Radiator drain plug washer - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Let the engine cool completely.
• Raise the front of the vehicle only if needed for easier drain access.
• Have a clean container ready to catch coolant.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Drain the coolant

• Use a drain pan under the radiator drain area.
• Open the radiator drain plug slowly and let the coolant drain out.
• If needed, remove the radiator cap only when the engine is fully cold.
• Save the coolant if it is clean.

Step 2: Remove the intake duct or access parts in the way

• Use a flat-blade screwdriver and 10mm socket to remove the air duct or nearby covers blocking access to the thermostat housing.
• Move the parts aside carefully so you do not crack any plastic clips.

Step 3: Disconnect the thermostat housing connections

• Use pliers to release hose clamps on the thermostat housing.
• Twist the hose gently before pulling it off the housing.
• Be ready for a little more coolant to spill.

Step 4: Remove the thermostat housing

• Use a 12mm socket, ratchet, and short extension to remove the housing bolts.
• Lift the housing away and remove the old thermostat and seal.
• Note the thermostat orientation before removal.

Step 5: Install the new thermostat

• Install the new thermostat in the same direction as the old one.
• Install the new thermostat housing gasket or seal.
• Make sure the sealing surface is clean and dry before reassembly.

Step 6: Reinstall the thermostat housing

• Set the housing in place by hand first.
• Use a 12mm socket to tighten the bolts evenly.
• Torque to 10-12 Nm (89-106 in-lbs).

Step 7: Reconnect hoses and reassemble

• Push the hoses fully back onto the housing.
• Use pliers to move the hose clamps back into place.
• Reinstall the intake duct and any covers using a 10mm socket and screwdriver.

Step 8: Refill and bleed the cooling system

• Use a funnel to refill with the correct coolant.
• Fill slowly to reduce trapped air.
• Start the engine and let it idle with the heater set to hot.
• Watch the coolant level and top off as air escapes.
• Install the radiator cap once the level stabilizes and no more air burps out.

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✅ After Repair

• Check for coolant leaks at the thermostat housing and hoses.
• Watch engine temperature during the first test drive.
• Confirm the heater blows hot air and the temperature stays steady.
• Recheck coolant level after the engine cools down.

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💰 DIY vs Shop Cost

Shop Cost: $350-$650 (parts + labor)

DIY Cost: $70-$160 (parts only)

You Save: $280-$490 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.