How to Replace a Radiator or Heater Hose - dummies

How to Replace a Radiator or Heater Hose

By Deanna Sclar

The basic process of changing a hose is quite simple. If the hose is a radiator or heater hose, to catch the coolant and water that will run out of the system, you’ll need a bucket or pan that holds at least two gallons of liquid and will fit under the radiator drain valve (called the petcock) that drains the radiator.

Follow these steps to replace a radiator or heater hose:

Make sure that the parking brake is on and that the car is in Neutral or Park before you start work.

  1. Remove the pressure cap from the radiator or coolant reservoir and place a bucket or drain pan under the radiator drain valve.

    You’ll need a bucket or pan that holds at least two gallons of liquid.

  2. Open the drain valve.

    Allow the coolant to drain into the container, and then close the valve.

  3. Remove the clamps at both ends of the hose.

    Clamps are cheap so buy new ones. If you can’t remove them easily, cut them off.


  4. Twist the hose to remove it, and use the container to catch the liquid that drains from it.

    Be gentle when removing the hose. If you’re not careful, you could damage the radiator.

  5. Clean the fittings.

    Use any degreaser or just a damp clean rag to clean the fittings that the new hose will attach to.

  6. Install the new hose.

    Attach and clamp one end securely in place before you tackle the other end. Make sure that the hose won’t interfere with any moving parts or touch the engine when it’s hot, and that the clamps are tight.

  7. If the coolant that you drained is fairly new and your container was clean, pour the liquid back into the system; otherwise, refill the system with a 50/50 mix of fresh coolant and water.

    Be sure to dispose of the old stuff safely.

  8. Start the engine and add more water and coolant as the level in the radiator drops.

    Don’t fill the radiator to the top of the neck or the coolant reservoir up to the “MAX” line until the thermostat opens. When the upper hose is hot, the thermostat has opened. Then it’s okay to top off the radiator or the reservoir.

  9. Replace the pressure cap.

    If your engine is the type that needs to be bled, do so now, following the instructions in the owner’s manual or service manual for your vehicle.

Before you consider the job complete, run the engine and double-check that the clamps are nice and tight so that no liquid leaks out.