Ford Mustang (1999-2004) Service Manual: Heater Hose Coupling

Special Tool(s)

Remover, Heater Hose Inlet Tube 412-042 (T85T-18539-AH)
Disconnect Tool, Heater Hose 412-127


Item Specification


CAUTION: Do not attempt to install a new bushing, spacer or O-rings in the heater hose coupling; damage to the heater hose coupling can result. If the heater hose coupling is the cause of a coolant leak, the affected heater hose must be replaced as an assembly.

1. WARNING: The engine must be off, fully cool and the cooling system fully depressurized before attempting to disconnect any heater water hoses. Failure to comply with this warning can result in serious injury or burns from hot liquid escaping out of the engine cooling system.

Depressurize the engine cooling system.

2. Push the heater hose toward the tube to fully expose the locking tabs.

3. NOTE: When compressing the white coupling retainer with the special tool, the special tool must be perpendicular to and on the highest point of the coupling.

NOTE: If the heater hose coupling is accessible, the retainer tabs can be compressed by hand to disconnect the heater hose.

Push the special tool over the coupling retainer windows to compress the retainer locking tabs.

Heater Hose Coupling

4. NOTE: A slight twisting motion while pulling on the heater water hose may be necessary to assist in the removal.

Pull the heater hose away from the heater core tube.

Heater Hose Coupling

5. Spread the retainer tabs apart and slide the retainer off the tube.

  • Discard the retainer.

Heater Hose Coupling


1. Clean the tubes and lubricate with coolant hose lubricant or plain water.

2. Install a new coupling retainer (18D434) into the heater hose coupling housing.

Heater Hose Coupling

3. Push the heater hose coupling onto the tube.

Heater Hose Coupling

4. Make sure the heater hose coupling is fully engaged by lightly pulling on the heater hose.

    1. Install the A/C tube lock coupling spring. 2. Lubricate the inside of the coupling with PAG Refrigerant Compressor Oil (R-134a Systems) or equivalent. 3. CAUTION: Use only the new O-ring seals ...

    Air Conditioning Line (Peanut) Fitting
    Disconnect 1. CAUTION: Support the female fitting with a wrench to prevent the tubes from twisting. Remove the nut from the peanut fitting. 2. Pull the peanut fitting apart. 3. CAUTION: Do not us ...

    Other materials:

    Cleaning leather seats
    • Remove dust and loose dirt with a vacuum cleaner. • Clean spills and stains as quickly as possible. • For routine cleaning, wipe the surface with a soft, damp cloth. For more thorough cleaning, wipe the surface with a mild soap and water solution. In C ...

    Fuel Charging And Controls
    The fuel injection supply manifold (9F792): delivers fuel to the fuel injector. receives fuel from the fuel supply line. The throttle body (9E926): controls air supply to the upper intake manifold (9424) by positioning the throttle plate. connects the ...

    Driving through water
    WARNING: Drive through water in an emergency only, and not as part of normal driving. WARNING: Engine damage can occur if water enters the air filter. Note: Driving through deep water may allow water into the transmission or air intake and can cause internal v ...