Heater Hoses

Replace the heater inlet and outlet hoses connecting the engine cooling system to the heater core, including draining coolant and refilling the system.

Warnings

Tools required

Parts

• Heater inlet hose (5/8" or 3/4" depending on routing) × 1 — Gates 18236 or equivalent
• Heater outlet hose (5/8" or 3/4" depending on routing) × 1 — Gates 18236 or equivalent
• Hose clamps (worm-gear style) × 4 — Use OEM specification

Fluids

• Ethylene glycol green 50/50 coolant — 4 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level ground and apply parking brake
3. Place drain pan beneath radiator drain petcock on driver's side of radiator
4. Open the hood and secure it in the open position
5. Locate the heater hoses: one runs from the intake manifold or cylinder head to the heater core inlet on the firewall, the other returns from the heater core to the water pump

Procedure

1. 1

   Drain the cooling system
   Open the radiator drain petcock located at the bottom of the radiator (typically driver's side, but may vary by radiator type). Turn counterclockwise to open. Allow coolant to drain into the pan until the level drops below the heater hose connections. You will need to drain approximately 2-3 quarts. If desired, remove the radiator cap to speed draining, but only after confirming the system is completely cool.
2. 2

   Remove the heater inlet hose clamp
   Locate the heater inlet hose connection at the intake manifold fitting (typically near the thermostat housing/front of engine on the 302). Verify the actual fitting location on your vehicle before proceeding. Using hose clamp pliers or a flat blade screwdriver, loosen the worm-gear clamp securing the hose to the engine fitting. Slide the clamp back along the hose away from the connection point at least 2 inches.
3. 3

   Remove the heater inlet hose from engine
   Twist the hose back and forth while pulling to break it free from the engine fitting. If the hose is stuck due to age, carefully use a utility knife to make a single lengthwise cut in the last inch of hose on the fitting, being careful not to score the metal nipple. Remove the hose and any remaining rubber from the fitting. Residual coolant will drain; have towels ready.
4. 4

   Remove the inlet hose from firewall connection
   At the firewall heater core inlet connection, loosen the worm-gear clamp using a screwdriver or pliers. Slide the clamp back along the hose. Twist and pull the hose off the heater core nipple. If stuck, use the same cutting technique as in the previous step. Remove the entire inlet hose.
5. 5

   Remove the heater outlet hose clamp at water pump
   Locate the heater outlet hose connection at the water pump (driver's side of engine, front). Loosen the worm-gear clamp and slide it back along the hose at least 2 inches away from the water pump fitting.
6. 6

   Remove the heater outlet hose from water pump
   Twist and pull the outlet hose off the water pump nipple. If stuck, carefully cut the last inch of hose lengthwise to remove it without damaging the fitting. Clean any old rubber residue from the water pump nipple with a rag.
7. 7

   Remove the outlet hose from firewall connection
   At the firewall heater core outlet connection, loosen the worm-gear clamp with a screwdriver or pliers. Slide the clamp back and twist the hose off the heater core nipple. Remove the entire outlet hose. Inspect both heater core nipples on the firewall for corrosion or damage.
8. 8

   Clean all hose connection points
   Using a rag or wire brush, clean all four hose connection points: the engine intake manifold/cylinder head fitting, the water pump nipple, and both heater core nipples on the firewall. Remove any old rubber, corrosion, or debris. The surfaces should be smooth and clean for proper seal.
9. 9

   Install new heater inlet hose
   Slide a new worm-gear clamp onto the inlet hose with the screw mechanism accessible. Route the new inlet hose from the engine fitting to the heater core inlet on the firewall, following the original path. Push the hose firmly onto the engine fitting until it bottoms out (approximately 1.5 inches onto the nipple). Position the clamp 0.5 inches from the end of the hose and tighten securely with a screwdriver until snug but not overtightened.
10. 10

    Connect inlet hose to firewall
    Slide a new clamp onto the firewall end of the inlet hose. Push the hose firmly onto the heater core inlet nipple until it seats completely. Position the clamp 0.5 inches from the hose end and tighten securely with a screwdriver. Ensure the hose routing does not contact any sharp edges or hot exhaust components.
11. 11

    Install new heater outlet hose
    Slide a new worm-gear clamp onto the outlet hose. Route the new outlet hose from the water pump to the heater core outlet on the firewall, following the original path. Push the hose firmly onto the water pump nipple until fully seated. Position the clamp 0.5 inches from the hose end and tighten securely.
12. 12

    Connect outlet hose to firewall
    Slide a new clamp onto the firewall end of the outlet hose. Push the hose firmly onto the heater core outlet nipple until fully seated. Position the clamp 0.5 inches from the hose end and tighten securely. Verify both heater hoses have adequate clearance from moving parts, belts, and exhaust manifolds.
13. 13

    Close radiator drain and refill cooling system
    Close the radiator drain petcock by turning clockwise until snug. Using a funnel, pour fresh 50/50 ethylene glycol green coolant into the radiator until it reaches the bottom of the filler neck. Fill slowly to allow air to escape. Install the radiator cap.
14. 14

    Bleed air from cooling system
    Start the engine and allow it to idle with the heater controls set to maximum heat and fan on. Watch the temperature gauge. As the thermostat opens and air bleeds from the system, the coolant level may drop. Turn off the engine when it reaches normal operating temperature (approximately 10-15 minutes). Allow to cool for 30 minutes, then recheck radiator coolant level and top off as needed.

Reassembly

1. Verify all four hose clamps are tightened securely
2. Confirm proper coolant level in radiator after bleeding procedure
3. Inspect all hose connections for coolant leaks after the first heat cycle

Verification

• Start the engine and allow it to reach normal operating temperature while monitoring for leaks at all four hose connections
• Verify heater produces hot air when controls are set to maximum heat, confirming proper coolant flow through heater core
• Check for any coolant drips on the ground after the vehicle has been parked overnight
• Recheck radiator coolant level after 24 hours of driving and top off if needed
• Verify engine temperature gauge reads normal during operation with no overheating

More procedures for this vehicle