🔧 Forester - Radiator Hose Replacement

Replacing a radiator hose stops coolant leaks and prevents overheating. On your Forester there’s typically an upper radiator hose (engine to radiator) and a lower radiator hose (radiator to engine), and the steps are very similar for both.

Difficulty Level: Intermediate | Estimated Time: 1.0-2.0 hours

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⚠️ Safety & Precautions

• ⚠️ Never open the radiator cap on a hot engine; hot coolant can cause severe burns.
• ⚠️ Keep coolant off belts and electrical connectors; wipe spills immediately.
• ⚠️ Coolant is toxic—catch it in a drain pan and dispose of it properly.
• ⚠️ If you raise the front end, support it with jack stands before going underneath.
• 🔋 Battery disconnect is not required for this job.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• Drain pan (at least 10-quart)
• Funnel
• Spill-free coolant funnel kit (specialty)
• Hose clamp pliers (specialty)
• Channel-lock pliers
• Pick tool
• Flat-blade screwdriver
• 10mm socket
• Ratchet
• Extension (3-inch)
• Trim clip removal tool
• Rags

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Upper radiator hose - Qty: 1
• Lower radiator hose - Qty: 1
• Radiator hose clamps - Qty: 4
• Engine coolant (Subaru Super Coolant equivalent, blue premix) - Qty: 2-3 gallons
• Distilled water - Qty: 1 gallon

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📋 Before You Begin

• Park on level ground, set the parking brake, and let the engine cool completely (preferably 2+ hours).
• Set the cabin heat to HOT (so coolant can circulate through the heater core during bleeding).
• If you’ll be working from below, chock the rear wheels with wheel chocks and raise/support the front using a floor jack and jack stands.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the lower engine cover (undertray) if needed

• Use a trim clip removal tool to remove plastic clips.
• Use a 10mm socket with a ratchet and 3-inch extension to remove any 10mm bolts.
• Set the undertray and hardware aside where you won’t lose them.

Step 2: Safely relieve cooling system pressure

• Place a rag over the radiator cap area.
• Slowly loosen the cap only if the engine is fully cool; use a rag for grip and splash protection.

Step 3: Drain enough coolant to get the hose off without a huge spill

• Position a drain pan (at least 10-quart) under the radiator drain area.
• Open the radiator drain to lower the coolant level; use a flat-blade screwdriver only if needed for the drain fitting.
• Drain until the coolant level is below the hose you’re replacing (upper hose = drain a little; lower hose = drain more).

Step 4: Remove the radiator hose clamps

• Use hose clamp pliers (specialty) to squeeze the spring clamp tabs and slide the clamp back onto the hose.
• If your hose uses screw-style clamps, loosen them with a flat-blade screwdriver.
• Tip: Take a quick photo for clamp positioning.

Step 5: Remove the old hose

• Twist the hose to break it free. Use channel-lock pliers gently if it’s stuck.
• If it’s really stuck, carefully work around the hose end with a pick tool to loosen it (don’t gouge the radiator or engine outlet).
• Pull the hose off and let remaining coolant drain into the drain pan.

Step 6: Inspect and clean the hose connections

• Wipe the radiator and engine hose nipples with rags until clean and smooth.
• Check the radiator neck for cracks or heavy corrosion; don’t reinstall a hose onto a damaged neck.

Step 7: Install the new hose and clamps

• Slide new radiator hose clamps onto the new hose before installing the hose.
• Push the new hose fully onto the radiator/engine fittings until it seats against the stop/bead.
• Use hose clamp pliers (specialty) to position spring clamps in the same location as original (behind the bead on the fitting).

Step 8: Refill coolant

• Close the radiator drain.
• Install a spill-free coolant funnel kit (specialty) at the radiator fill neck and add engine coolant (Subaru Super Coolant equivalent, blue premix) using a funnel as needed.
• Fill the overflow reservoir to the FULL line.

Step 9: Bleed air from the system (critical)

• Start the engine and let it idle with the funnel in place; keep the heater set to HOT.
• As it warms up, watch for air bubbles in the funnel and keep coolant level topped up.
• Carefully squeeze the upper radiator hose by hand to help push trapped air out.
• Once the cooling fan cycles on/off and bubbles slow way down, shut the engine off and let it cool.
• Top off the radiator and overflow reservoir as needed.

Step 10: Reinstall the undertray

• Reinstall the undertray using the 10mm socket, ratchet, and trim clip removal tool (to re-seat clips).

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✅ After Repair

• Start the engine and check both ends of the replaced hose for seepage while idling.
• After a short drive, recheck for leaks and confirm the temperature gauge stays normal.
• When fully cold (next morning), recheck the overflow reservoir level and top off if needed.
• If you hear gurgling behind the dash or the heater blows cold, you likely still have air—repeat the bleed step.

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💰 DIY vs Shop Cost

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

DIY Cost: $50-$180 (parts only)

You Save: $200-$320 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-2.0 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.