🔧 Forester - Radiator Hose Replacement

This guide covers replacing the upper and/or lower radiator hose on your Forester. A radiator hose carries coolant between the engine and radiator, and it should be replaced if it is swollen, cracked, leaking, soft, or oil-soaked.

Difficulty Level: Beginner | Estimated Time: 1-2 hours

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⚠️ Safety & Precautions

• ⚠️ Only work on the cooling system when the engine is completely cold. Hot coolant can cause serious burns.
• ⚠️ Do not remove the radiator cap while the engine is hot or warm.
• ⚠️ Coolant is poisonous to people and animals. Catch all drained coolant and dispose of it properly.
• ⚠️ Keep coolant off belts and painted surfaces. Rinse spills with clean water.
• ⚠️ Battery disconnect is not required for this repair.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Drain pan 2-gallon minimum
• Flat-blade screwdriver
• Slip-joint pliers
• Hose clamp pliers (specialty)
• 10mm socket
• 3/8-inch ratchet
• Plastic trim clip remover
• Funnel spill-free coolant fill kit (specialty)
• Shop towels
• Flashlight

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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, if replacing lower hose
• Radiator hose clamps - Qty: 2 per hose
• Subaru Super Coolant premix or equivalent blue phosphate-based coolant - Qty: 1-2 gallons
• Distilled water - Qty: 1 gallon, if using concentrate only

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📋 Before You Begin

• Park your Forester on level ground and set the parking brake.
• Let the engine sit until it is fully cold, ideally several hours.
• Open the hood and locate the hose you are replacing.
• The upper radiator hose runs from the top of the radiator to the engine.
• The lower radiator hose runs from the bottom of the radiator to the engine water pump area.
• A hose clamp is the spring or screw-style band that squeezes the hose tight onto the metal or plastic fitting.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Let the Engine Cool and Remove the Radiator Cap

• Put on safety glasses and nitrile gloves.
• Confirm the engine is completely cold by carefully touching the upper radiator hose with your gloved hand.
• Use your hand to slowly remove the radiator cap.
• If you hear pressure escaping, stop and wait longer before continuing.

Step 2: Position the Drain Pan

• Place the drain pan 2-gallon minimum under the lower radiator area.
• Use a flashlight to locate the radiator drain plug at the lower radiator tank.
• If access is tight, use the plastic trim clip remover to remove lower splash shield clips as needed.

Step 3: Drain Some Coolant

• Use your hand or a flat-blade screwdriver if needed to carefully open the radiator drain plug.
• Drain enough coolant so the level is below the hose you are replacing.
• For upper hose replacement, draining about 1 gallon is usually enough.
• For lower hose replacement, drain the radiator fully.
• Close the radiator drain plug by hand until snug. Do not overtighten plastic drain plugs.
• Plastic plugs crack if forced.

Step 4: Remove Any Access Pieces if Needed

• Use a 10mm socket and 3/8-inch ratchet to remove any air intake duct fasteners blocking hose access.
• Move the duct aside gently.
• Use the plastic trim clip remover for any plastic clips.
• Keep all bolts and clips in a small tray or safe spot.

Step 5: Loosen the Hose Clamps

• If your Forester has spring clamps, use hose clamp pliers or slip-joint pliers to squeeze the clamp ears together.
• A spring clamp is a factory clamp that opens when squeezed and tightens by spring pressure.
• Slide each clamp back several inches onto the hose.
• If screw clamps are installed, use a flat-blade screwdriver to loosen them.
• Take a photo before removing parts.

Step 6: Remove the Old Radiator Hose

• Use your hand to twist the hose gently to break it loose.
• If it is stuck, use a flat-blade screwdriver very carefully between the hose and fitting to loosen the rubber edge.
• Do not pry hard on the radiator neck because it can crack.
• Pull the hose off both fittings and aim any remaining coolant into the drain pan 2-gallon minimum.
• If the hose will not come off, use the flat-blade screwdriver to work around the edge again, then twist and pull.

Step 7: Clean and Inspect the Hose Fittings

• Use shop towels to wipe the radiator neck and engine-side fitting clean.
• Use a flashlight to inspect for cracks, corrosion, leftover rubber, or broken plastic.
• If the radiator neck is cracked, the radiator must be replaced before installing the hose.
• Do not use grease, oil, or sealant on the hose ends.

Step 8: Install the New Radiator Hose

• Compare the new hose to the old hose before installation.
• Use your hands to slide the new hose fully onto the radiator fitting and engine fitting.
• Make sure the hose is not twisted or rubbing against belts, pulleys, fans, or sharp edges.
• Use hose clamp pliers or slip-joint pliers to move spring clamps back into their original clamp marks.
• If using screw clamps, tighten them with a flat-blade screwdriver until snug, but do not crush the hose.
• Clamp behind the raised bead.

Step 9: Reinstall Access Pieces

• Reinstall any air intake duct pieces removed earlier.
• Use a 10mm socket and 3/8-inch ratchet to tighten the fasteners snugly.
• Reinstall plastic clips using your hand or the plastic trim clip remover.

Step 10: Refill the Cooling System

• Install the funnel spill-free coolant fill kit into the radiator filler neck.
• Slowly pour Subaru Super Coolant premix or equivalent blue phosphate-based coolant into the funnel.
• Fill until the radiator stays full and the funnel has coolant in it.
• Fill the coolant overflow reservoir to the “FULL” mark.
• If using coolant concentrate, mix only with distilled water to the correct 50/50 ratio before filling.

Step 11: Bleed Air from the Cooling System

• Leave the funnel spill-free coolant fill kit installed.
• Start the engine and let it idle.
• Set the cabin heater to full hot and blower to low.
• Watch for air bubbles coming up through the funnel.
• Use your gloved hand to gently squeeze the upper radiator hose several times to help move trapped air.
• When the radiator fan cycles on and warm air blows from the heater, most air has been removed.
• Keep the funnel filled so air is not pulled back into the system.

Step 12: Cap the Radiator and Check for Leaks

• Turn the engine off.
• Use shop towels to clean spilled coolant around the radiator neck.
• Remove the funnel spill-free coolant fill kit following the funnel tool instructions.
• Install the radiator cap by hand until fully locked.
• Use a flashlight to inspect both hose ends for leaks.

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✅ After Repair

• Run the engine until fully warm and confirm the temperature gauge stays normal.
• Check that the heater blows warm air. Cold air can mean trapped air in the cooling system.
• After the first drive, let the engine cool completely and recheck the coolant level in the radiator and overflow reservoir.
• Top off with the same coolant if needed.
• Inspect the hose clamps again after the first heat cycle.
• Dispose of old coolant at a recycling center or auto parts store that accepts used coolant.

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💰 DIY vs Shop Cost

Shop Cost: $180-$350 per hose, parts + labor

DIY Cost: $35-$120, parts only

You Save: $145-$230 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1-1.5 hours.

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🎯 Ready to get started?

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