Heater Hoses

Replace heater hoses on the 2007 Ram 3500 with 5.9L Cummins diesel engine to restore proper coolant flow to the heating system.

Warnings

Tools required

Parts

• Heater inlet hose × 1 — Use OEM specification
• Heater outlet hose × 1 — Use OEM specification
• Hose clamps (assorted) × 4 — Use OEM specification
• HOAT coolant concentrate × 1 — Mopar OAT or compatible

Fluids

• HOAT coolant 50/50 — 4 qt

Preparation

1. Park vehicle on level surface and allow engine to cool completely for at least 2 hours
2. Verify coolant temperature is cool to the touch at radiator cap
3. Place drain pan under vehicle near radiator petcock
4. Remove negative battery cable to prevent accidental fan activation
5. Remove engine cover if equipped

Procedure

1. 1

   Drain cooling system
   Slowly remove the radiator cap by turning counterclockwise. Open the radiator petcock/drain located at the bottom of the radiator (verify side) and drain coolant into the drain pan until the level drops below the heater hose connections. Close petcock when coolant level drops below heater hose connections. Close petcock when coolant level drops below heater hose connections.
2. 2

   Access heater hoses at engine
   Locate the heater hoses on the engine. On the 5.9L Cummins the inlet (supply) hose typically connects near the rear of the cylinder head and the outlet (return) hose connects to the water pump area; verify actual routing on your vehicle before disconnecting. Use a flashlight to trace the hoses from the firewall to their engine connections.
3. 3

   Remove inlet hose clamp at engine
   Using hose clamp pliers or a flat blade screwdriver, loosen the clamp securing the heater inlet hose to the water pump or thermostat housing connection. Slide the clamp back along the hose at least 2 inches away from the fitting.
4. 4

   Remove inlet hose from engine
   Twist the hose back and forth while pulling to break the seal and remove it from the fitting. If the hose is stuck, carefully use a pick tool between the hose and fitting to break the seal. Allow remaining coolant to drain into the pan. Inspect the fitting for damage or corrosion.
5. 5

   Remove outlet hose clamp at engine
   Locate the heater outlet hose connection on the cylinder head or block. Loosen the clamp securing the outlet hose using hose clamp pliers or screwdriver. Slide the clamp back along the hose away from the fitting.
6. 6

   Remove outlet hose from engine
   Twist and pull the outlet hose to remove it from the engine fitting. Use a pick tool if necessary to break the seal. Allow coolant to drain completely.
7. 7

   Access heater hoses at firewall
   Move to the firewall where both heater hoses pass through to connect to the heater core (typically on the passenger side of this vehicle). Locate where both heater hoses pass through the firewall to connect to the heater core. There may be a rubber grommet surrounding the hoses at the firewall penetration.
8. 8

   Remove hose clamps at firewall
   Loosen the clamps at both heater core connections where the hoses connect to the metal pipes protruding from the firewall. Slide clamps back along the hoses. Note the routing and orientation of both hoses for proper installation.
9. 9

   Remove old heater hoses
   Twist and pull both hoses from the heater core pipes at the firewall. Remove the hoses completely from the vehicle. If hoses are severely deteriorated, they may need to be cut away with a utility knife. Clean all fitting surfaces with a shop towel to remove old coolant residue and debris.
10. 10

    Install new inlet hose
    Route the new heater inlet hose from the firewall connection to the water pump or thermostat housing, following the same path as the original. Ensure the hose does not contact sharp edges or moving components. Slide new clamps onto the hose before connecting. Push the hose firmly onto both fittings until it bottoms out, approximately 1.5-2 inches onto each fitting.
11. 11

    Install new outlet hose
    Route the new heater outlet hose from the firewall to the cylinder head or block connection, matching the original routing. Slide new clamps onto the hose. Push the hose firmly onto both fittings until fully seated. Verify hoses do not contact exhaust components, belts, or pulleys.
12. 12

    Secure all hose clamps
    Position all four clamps approximately 0.5 inches from the end of each hose on the fitting. Tighten each clamp securely using hose clamp pliers or screwdriver until the hose cannot be twisted by hand. Do not overtighten spring-type clamps. Ensure worm-gear clamps are tightened evenly.
13. 13

    Refill cooling system
    Mix HOAT coolant (Mopar 5-year/100,000-mile, MS-9769) to 50/50 ratio with distilled water, or use pre-mixed 50/50 HOAT coolant. Using a funnel with adapter, slowly fill the cooling system through the radiator cap opening. Fill until coolant reaches the bottom of the filler neck. Allow time for coolant to settle and air bubbles to escape. Add coolant as needed.
14. 14

    Burp cooling system
    With the radiator cap still off, reconnect the negative battery cable. Start the engine and allow it to idle. Monitor coolant level and add as needed as air pockets are purged. Run the engine until the thermostat opens (coolant temperature reaches approximately 180°F) and the upper radiator hose becomes hot. Turn on the heater to maximum heat and high fan speed to purge air from the heater core.
15. 15

    Final fill and inspection
    With the engine still running, add coolant to bring the level to the bottom of the filler neck. Install the radiator cap and allow the engine to reach full operating temperature. Check all hose connections for leaks. Shut off the engine and allow it to cool. Recheck coolant level in both the radiator and overflow reservoir when cold, topping off as necessary.

Reassembly

1. Reinstall engine cover if previously removed
2. Verify all tools and shop towels are removed from engine bay
3. Properly dispose of old coolant according to local regulations
4. Check coolant level in overflow reservoir and fill to cold mark if needed

Verification

• Start engine and verify heater produces hot air at all fan speeds
• Check for coolant leaks at all four hose connections with engine at operating temperature
• Verify coolant level remains stable in overflow reservoir after multiple heat cycles
• Confirm upper and lower radiator hoses become hot, indicating proper coolant circulation
• Monitor coolant temperature gauge to ensure normal operating temperature is maintained

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle