This procedure covers the replacement of heater hoses on the 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine, including coolant draining, hose removal, and system refilling.

Warnings

Tools required

Parts

• Heater inlet hose × 1 — Use OEM specification
• Heater outlet hose × 1 — Use OEM specification
• Hose clamps (if replacing) × 4 — Worm gear or constant tension type
• Coolant (if needed for top-off) × 1 — Motorcraft Orange Coolant

Fluids

• Motorcraft Orange Coolant — 2 qt

Preparation

1. Ensure engine is completely cold before beginning work
2. Park vehicle on level ground and set parking brake
3. Disconnect negative battery cable to prevent accidental fan activation
4. Remove engine cover by pulling upward on cover - it is retained by grommets
5. Place drain pan under radiator drain plug location
6. Take photos of hose routing and clamp positions for reference during reinstallation

Procedure

1. 1

   Drain cooling system
   Locate the radiator drain plug on the lower passenger side of the radiator. Slowly open the drain plug and allow coolant to drain into the pan. Once draining slows, close the drain plug and torque to specification. If replacing only heater hoses, partial drain is sufficient - you do not need to drain the entire system.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)
2. 2

   Remove air intake components for access
   Disconnect the mass airflow sensor electrical connector. Loosen the hose clamp at the throttle body. Remove the air intake tube by releasing clamps and lifting upward. Set aside in a clean area. This provides necessary access to the heater hoses at the firewall and engine connections.
3. 3

   Locate and access heater hoses
   Identify the two heater hoses running from the engine (passenger side near thermostat housing and water pump area) to the firewall connections. The inlet hose connects to the water pump/thermostat housing area, and the outlet hose returns from the heater core. Trace both hoses completely to confirm routing before removal.
4. 4

   Remove heater hose at firewall connections
   Using hose clamp pliers, compress and slide the spring clamps away from the firewall connection points (or loosen worm gear clamps if equipped). Gently twist and pull the hoses off the heater core pipes at the firewall. Have shop towels ready as residual coolant will drain. If hoses are stuck, use a plastic pry tool to carefully break the seal - do not use excessive force that could damage heater core pipes.
   ⚠Heater core pipes are fragile. Excessive force can break the pipes inside the firewall, requiring expensive heater core replacement.
5. 5

   Disconnect heater inlet hose at engine
   Locate the heater inlet hose connection at the thermostat housing or water pump area on the passenger side of the engine. Compress or loosen the hose clamp and slide it away from the fitting. Twist and pull the hose off the fitting. Allow any remaining coolant to drain into your pan.
6. 6

   Disconnect heater outlet hose at engine
   Locate the heater outlet hose connection point (typically at the water pump or lower coolant passage). Compress or loosen the hose clamp and slide away from the connection. Remove the hose from the fitting, again collecting any residual coolant. Remove both hoses completely from the vehicle.
7. 7

   Inspect fittings and prepare new hoses
   Inspect all heater core pipes and engine fittings for corrosion, damage, or residue buildup. Clean fittings with a wire brush if needed - they should be smooth and free of debris. Inspect new hoses to ensure they match the old hoses in length, diameter, and bend configuration. Transfer any insulators or protective sleeves from old hoses to new hoses if applicable.
8. 8

   Install new heater inlet hose
   Route the new heater inlet hose from the engine connection to the firewall, following the exact path of the original hose. Slide new hose clamps onto the hose before installation if using worm gear type. Push the hose firmly onto the engine fitting first, ensuring it is fully seated past the bead. Then connect to the firewall fitting, again ensuring full engagement.
9. 9

   Install new heater outlet hose
   Route the new heater outlet hose from the firewall to the engine connection point. Install hose clamps before connecting if needed. Connect the hose to the firewall heater core pipe first, pushing firmly until fully seated. Then connect the engine end, ensuring the hose is fully engaged on the fitting.
10. 10

    Secure all hose clamps
    Position all hose clamps approximately 1/4 inch from the end of each hose, centered over the fitting bead. If using spring clamps, position them properly and compress to secure. If using worm gear clamps, tighten to the specified torque. Ensure clamps are not overtightened, which can damage hoses.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
11. 11

    Reinstall air intake components
    Reinstall the air intake tube, ensuring all connections are properly aligned. Tighten the throttle body hose clamp securely. Reconnect the mass airflow sensor electrical connector until it clicks into place. Verify all intake components are secure.
12. 12

    Refill cooling system
    Using a funnel, pour Motorcraft Orange Coolant into the coolant reservoir and radiator fill neck (if accessible). Fill the reservoir to the COLD FILL mark. Start the engine and allow it to reach operating temperature with the heater set to maximum heat. Monitor coolant level and add as needed as air purges from the system. Squeeze heater hoses to help release trapped air.
    ⚠Monitor engine temperature closely during refill process. If temperature rises abnormally, shut off engine immediately to prevent overheating.
13. 13

    Burp cooling system and check for leaks
    With the engine at operating temperature, rev the engine to 2000-2500 RPM several times to help purge remaining air. Turn off the engine and allow to cool. Check coolant level when cold and top off to the COLD FILL mark if needed. Inspect all heater hose connections for signs of leakage. Wipe connections dry and check again after a short test drive.

Reassembly

1. Reinstall engine cover by aligning grommets and pressing down firmly until seated
2. Reconnect negative battery cable
3. Verify all tools and parts have been removed from engine bay
4. Properly dispose of old coolant and used heater hoses according to local regulations

Verification

• Start engine and verify heater produces hot air at idle and at higher RPM
• Check for coolant leaks at all four heater hose connections (two at firewall, two at engine)
• Verify coolant level is at COLD FILL mark when engine is cold
• Confirm no check engine light or temperature warning lights are illuminated
• Test drive vehicle and monitor temperature gauge - it should remain in normal range
• Recheck all connections after first drive and top off coolant if level has dropped slightly

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