🔧 ILX - Thermostat Replacement

The thermostat controls coolant flow so your engine warms up quickly and then stays at the right operating temperature. Replacing it means draining some coolant, removing the thermostat housing at the lower radiator hose, installing the new thermostat with a new seal, then refilling and bleeding air from the cooling system.

Assumption: Your ILX has the common K24 layout where the thermostat sits in the housing at the engine end of the lower radiator hose.

Difficulty Level: Intermediate | Estimated Time: 1.5-3 hours

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⚠️ Safety & Precautions

• ⚠️ Never open the radiator cap on a hot engine; hot coolant can spray and burn you.
• ⚠️ Support the car with jack stands if you raise it; never rely on a floor jack alone.
• ⚠️ Keep hands clear of the radiator fan; it can turn on unexpectedly.
• ⚠️ Catch and dispose of coolant properly; it’s toxic to people and pets.
• Battery disconnect is not required, but if your hands will be near the fan wiring, disconnect the negative battery terminal for extra safety.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 2-ton minimum)
• Jack stands (rated 2-ton minimum)
• Wheel chocks
• Drain pan (at least 10-quart)
• Funnel
• 8mm nut driver
• 10mm socket
• 12mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3" extension
• 6" extension
• Torque wrench (5-60 Nm range)
• Slip-joint pliers
• Hose clamp pliers
• Trim clip removal tool
• Plastic gasket scraper
• Shop towels
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Engine thermostat - Qty: 1
• Thermostat O-ring seal - Qty: 1
• Honda/Acura premixed coolant (Type 2 equivalent) - Qty: 1-2 gallons
• Lower radiator hose clamp - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and place wheel chocks behind the rear wheels.
• Let the engine cool fully (minimum 2-3 hours). The upper radiator hose should feel cool.
• Set the climate controls to Heat = HI and Fan = Low so coolant can flow through the heater core during bleeding.
• If you raise the front of the car, use a floor jack and support it with jack stands at the proper jack points.
• Place a drain pan under the radiator area before opening any drain or hose.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the intake duct for access

• Open the hood and use an 8mm nut driver to loosen the intake duct clamps.
• Use a 10mm socket and 1/4" drive ratchet to remove any intake duct mounting bolts, then lift the duct out.
• Take a photo first for reassembly.

Step 2: Drain coolant from the radiator

• Remove the radiator cap only if the engine is cool. Use nitrile gloves and turn it slowly to relieve any leftover pressure.
• If equipped with an under-cover, remove clips/bolts using a trim clip removal tool and 10mm socket.
• Position your drain pan under the radiator drain.
• Open the radiator drain using slip-joint pliers if needed, and let coolant drain.
• Close the drain when finished (snug only; do not over-tighten plastic drains).

Step 3: Locate the thermostat housing

• Follow the lower radiator hose to the engine; the thermostat sits behind the housing where that hose connects.
• Use a flashlight to identify the housing bolts and hose clamp position.
• Use shop towels to protect nearby connectors from spilled coolant.

Step 4: Remove the lower radiator hose from the housing

• Use hose clamp pliers to compress the spring clamp and slide it back on the hose.
• Twist the hose gently to break it loose, then pull it off the housing.
• Hose clamp pliers are pliers that lock the clamp open so you don’t fight spring tension.

Step 5: Remove the thermostat housing

• Place the drain pan under the housing; more coolant will spill.
• Use a 10mm socket, 3/8" drive ratchet, and a 3" extension to remove the housing bolts.
• Pull the housing straight off. If it sticks, tap lightly with your hand—do not pry hard on aluminum.

Step 6: Replace the thermostat and seal

• Note how the old thermostat sits (spring side toward the engine) before removing it.
• Remove the thermostat and the old O-ring seal by hand.
• Clean the mating surfaces using a plastic gasket scraper and shop towels.
• Install the new thermostat and new O-ring seal. Make sure the seal is fully seated and not twisted.

Step 7: Reinstall the thermostat housing

• Reinstall the housing by hand-starting the bolts to avoid cross-threading.
• Use a torque wrench and 10mm socket to tighten evenly.
• Torque to 12 Nm (9 ft-lbs).

Step 8: Reconnect the lower radiator hose

• Push the hose fully onto the housing until it seats against the stop.
• Use hose clamp pliers to position the clamp back in its original spot.
• If the clamp feels weak or distorted, replace it with the new lower radiator hose clamp.

Step 9: Refill coolant

• Insert a funnel and slowly refill the radiator with Honda/Acura Type 2 equivalent premixed coolant.
• Fill the overflow reservoir to the MAX line.
• Reinstall the radiator cap once the radiator stays full.

Step 10: Bleed air from the cooling system

• Start the engine and let it idle. Keep the climate set to Heat = HI.
• Watch the temperature gauge and look for leaks at the housing and hose.
• After a few minutes, the upper radiator hose should get hot as the thermostat opens.
• Shut the engine off, let it cool, then recheck the reservoir level and top off as needed using a funnel.
• Bleeding means removing trapped air so the engine doesn’t overheat.

Step 11: Reinstall the intake duct and under-cover

• Reinstall the intake duct and tighten clamps using an 8mm nut driver.
• Reinstall the under-cover using a trim clip removal tool and 10mm socket.

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✅ After Repair

• Let the engine reach normal operating temperature and confirm the heater blows hot air.
• Check for leaks around the thermostat housing and the lower radiator hose connection.
• After the next full cool-down (later the same day or next morning), recheck the overflow reservoir and top off to MAX.
• If the temperature gauge rises abnormally or you get no heat, shut it down and re-bleed (air is likely trapped).

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💰 DIY vs Shop Cost

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

DIY Cost: $60-$180 (parts only)

You Save: $290-$470 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3 hours.

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🎯 Ready to get started?

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