Heater Hoses

Replace the heater inlet and outlet hoses connecting the engine water pump and intake manifold to the heater core, including draining and refilling the cooling system.

Warnings

Tools required

Parts

• Heater inlet hose (5/8" diameter) × 1 — Use OEM specification or Gates 18404
• Heater outlet hose (5/8" diameter) × 1 — Use OEM specification or Gates 18404
• Worm gear hose clamps (5/8" - 1" range) × 4 — Use OEM specification

Fluids

• DEX-COOL Extended Life (Orange) — 2 qt

Preparation

1. Park vehicle on level ground and allow engine to cool completely (minimum 2 hours after last operation).
2. Place drain pan beneath radiator drain petcock on passenger side of radiator lower tank.
3. Remove radiator cap slowly to release any residual pressure.
4. Locate heater hoses: inlet hose runs from water pump to heater core inlet (upper connection on firewall passenger side), outlet hose runs from heater core outlet (lower connection) to intake manifold.
5. Verify replacement hoses match original routing and length before beginning work.

Procedure

1. 1

   Drain cooling system
   Open the radiator drain petcock by turning counterclockwise. Allow approximately 3-4 quarts of coolant to drain into the pan. Close the petcock once coolant flow stops. This partial drain is sufficient for heater hose replacement without removing all coolant from the block.
2. 2

   Access heater hose connections at firewall
   From the engine bay, locate the two heater core connections protruding through the firewall on the passenger side, near the blower motor housing. The upper connection is the inlet, the lower is the outlet. You may need to remove the air cleaner assembly for better access.
3. 3

   Remove inlet hose clamps
   Using a flathead screwdriver or hose clamp pliers, loosen the worm gear clamps at both ends of the heater inlet hose (water pump to firewall inlet connection). Slide the clamps away from the connection points along the hose. Be prepared for residual coolant spillage.
4. 4

   Remove heater inlet hose
   Twist the inlet hose back and forth while pulling to break the seal at both connections. Remove the hose from the water pump nipple and the heater core inlet. If the hose is stuck, carefully cut it lengthwise with a utility knife and peel it off without damaging the metal nipples.
5. 5

   Remove outlet hose clamps
   Locate the heater outlet hose connecting the lower firewall connection to the intake manifold fitting (located near the thermostat housing/water outlet at the front of the intake). Loosen the worm gear clamps at both ends using a flathead screwdriver and slide them away from the connections.
6. 6

   Remove heater outlet hose
   Twist and pull the outlet hose to remove it from the heater core outlet and intake manifold connection. Again, if stuck, carefully cut and peel the old hose rather than risk damaging the fittings.
7. 7

   Clean hose connection surfaces
   Inspect all four metal hose nipples (water pump, intake manifold, and both firewall connections) for corrosion, damage, or old rubber residue. Note the available nipple length, as engagement depth is limited to the length of each fitting. Clean surfaces with a shop towel. Ensure no debris will interfere with the new hose seal.
8. 8

   Install new inlet hose clamps
   Slide two new worm gear clamps onto the new heater inlet hose before installation, positioning one clamp approximately 2 inches from each end of the hose.
9. 9

   Install heater inlet hose
   Route the new inlet hose from the water pump nipple to the upper heater core connection at the firewall. Push the hose firmly onto each nipple until it bottoms out (approximately 1.5-2 inches of engagement on each fitting). Ensure the hose routing does not interfere with belts, pulleys, or other moving components.
10. 10

    Secure inlet hose clamps
    Position each clamp approximately 0.5 inches from the end of each nipple, centered over the hose bead. Tighten the clamps until snug using a flathead screwdriver. Do not overtighten; the hose should compress slightly but not bulge excessively.
11. 11

    Install new outlet hose clamps
    Slide two new worm gear clamps onto the new heater outlet hose before installation, positioning one clamp approximately 2 inches from each end.
12. 12

    Install heater outlet hose
    Route the new outlet hose from the lower heater core connection at the firewall to the intake manifold fitting. Push the hose fully onto each nipple with the same 1.5-2 inch engagement. Verify the hose does not contact the exhaust manifold or other heat sources.
13. 13

    Secure outlet hose clamps
    Position and tighten each clamp on the outlet hose using the same technique as the inlet hose: 0.5 inches from the nipple end, snug but not overtightened.
14. 14

    Refill cooling system
    Using a funnel, pour conventional ethylene glycol (green) coolant into the radiator until the level reaches the bottom of the filler neck. Start the engine and allow it to warm to operating temperature with the radiator cap off. Add coolant as the level drops during thermostat opening and air purging. Monitor heater hose connections for leaks.
15. 15

    Bleed air from system
    With the engine at operating temperature, turn the heater controls to maximum heat and fan speed. Feel both heater hoses; both should be hot, indicating proper coolant flow. Continue adding coolant to maintain proper level. Once the coolant level stabilizes and no air bubbles emerge, install the radiator cap.

Reassembly

1. Reinstall air cleaner assembly if removed during procedure.
2. Check all hose clamps one final time for proper tightness.
3. Wipe down engine bay and firewall area to remove coolant residue.

Verification

• With engine at operating temperature, visually inspect all four hose connections for coolant seepage or drips.
• Verify heater output is strong and hot when heater controls are set to maximum, confirming proper coolant circulation through new hoses.
• Check coolant level in radiator after engine cools; top off if necessary.
• Re-check hose connections after 50-100 miles of driving and retighten clamps if needed.

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