🔧 Outback - Thermostat Replacement

Your Outback’s thermostat controls coolant flow to keep engine temperature stable. Replacing it usually means draining some coolant, swapping the thermostat and seal, then refilling and bleeding air so the engine doesn’t overheat.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

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⚠️ Safety & Precautions

• 🔥 Never open the radiator cap on a hot engine; let it cool fully.
• 🧪 Coolant is toxic—keep away from kids/pets and dispose properly.
• 🛠️ Support the vehicle on jack stands; never rely on a jack alone.
• ⚡ Battery disconnect is not required for this job.

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🔧 Required Tools

You'll need the following tools for this repair:

• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• Safety glasses
• Nitrile gloves
• Drain pan (at least 2-gallon)
• 10mm socket
• 3/8" ratchet
• 3/8" extension (6")
• Torque wrench (3/8")
• Hose clamp pliers
• Flathead screwdriver
• Trim clip removal tool
• Funnel
• Spill-free funnel kit (specialty)
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Engine thermostat - Qty: 1
• Thermostat seal (O-ring/gasket) - Qty: 1
• Engine coolant (Subaru Super Coolant equivalent, premixed) - Qty: 2 gallons
• Lower radiator hose clamp - Qty: 1 If yours is weak/rusted

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Let the engine cool completely (upper radiator hose should feel cool).
• Set the cabin heat to HOT (this helps coolant flow through the heater core during bleeding).
• Have a drain pan ready and plan where you’ll recycle used coolant.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise the front and remove the lower splash shield

• Use a floor jack (rated 3-ton minimum) to lift the front, then set it on jack stands (rated 3-ton minimum).
• Use a trim clip removal tool and flathead screwdriver to remove the clips/screws holding the lower engine splash shield (undertray), then remove the shield.

Step 2: Drain coolant to below thermostat level

• Place a drain pan (at least 2-gallon) under the radiator/engine front area.
• Slowly loosen the radiator cap to the first stop to release any residual pressure, then remove it fully. Use nitrile gloves and safety glasses.
• From underneath, use hose clamp pliers to move the lower radiator hose clamp back, then carefully twist and pull the hose off to drain coolant into the pan.
• Tip: Twist the hose to break it free.

Step 3: Remove the thermostat housing cover

• Follow the lower radiator hose to the engine-side connection (thermostat housing area).
• Use a 10mm socket, 3/8" ratchet, and 3/8" extension (6") to remove the thermostat housing cover bolts.
• Pull the cover off carefully—more coolant may spill, so keep the drain pan positioned underneath.

Step 4: Replace the thermostat and seal

• Remove the old thermostat and the old thermostat seal (O-ring/gasket).
• Wipe the sealing surfaces clean using shop towels. Do not gouge the metal.
• Install the new thermostat and new seal.
• Make sure the thermostat’s air-bleed “jiggle valve” (small loose pin/valve) is positioned at the top (12 o’clock) when installed.

Step 5: Reinstall thermostat cover and torque bolts

• Reinstall the housing cover.
• Start the bolts by hand first to avoid cross-threading.
• Use a torque wrench (3/8") with a 10mm socket to tighten evenly: Torque to 10 Nm (7.4 ft-lbs).

Step 6: Reconnect the lower radiator hose

• Push the hose fully onto the fitting.
• Use hose clamp pliers to move the clamp back into its original position.
• If the clamp feels weak or doesn’t clamp evenly, replace it with the new lower radiator hose clamp.

Step 7: Refill coolant and bleed air

• Install a spill-free funnel kit (specialty) or a funnel at the radiator fill neck.
• Slowly add engine coolant (Subaru Super Coolant equivalent, premixed) until full.
• Start the engine and let it idle. Keep the cabin heat set to HOT.
• As it warms up, watch for air bubbles escaping into the funnel and keep topping off so the radiator stays full.
• Carefully squeeze the upper radiator hose a few times to help push trapped air out.
• Once the engine reaches operating temperature and you feel heat from the vents, reinstall the radiator cap.
• Fill the coolant overflow reservoir to the proper “FULL” mark.

Step 8: Reinstall the undertray and lower the vehicle

• Reinstall the splash shield using the trim clip removal tool and flathead screwdriver.
• Use the floor jack (rated 3-ton minimum) to lift slightly, remove jack stands (rated 3-ton minimum), then lower the vehicle.

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✅ After Repair

• With the engine running, check the thermostat housing and lower hose area for leaks.
• Test drive and confirm the temperature gauge stays normal (no overheating).
• After it cools completely, recheck the radiator level and overflow reservoir and top off if needed.
• Over the next 1–2 drives, recheck for small leaks and coolant level changes (leftover air can burp out).

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💰 DIY vs Shop Cost

Shop Cost: $250-$500 (parts + labor)

DIY Cost: $35-$90 (parts only)

You Save: $160-$465 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 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.