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How to Repair a Car Heater Hose

It's a good idea to keep a heater hose repair kit in your car (and learn how to use it) in the event of a roadside disaster.

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Heater hose repair - overheating carPhoto: Shutterstock

How to Prepare for Emergency Heater Hose Repair

You’re driving along running just a bit late for an appointment when steam starts belching up through the edges of the hood. Your car has just blown a heater hose and the coolant is vapourizing as it drains onto the hot engine. Well, we can’t make you feel any better about what just happened, but we can help you get back on the road in a reasonable amount of time.

If your car is more than six years old, no doubt your radiator and heater hoses have seen better days. The next time you’re in the auto supply store, pick up a kit containing a heater hose coupling and a pair of clamps. This heater hose repair kit doesn’t cost much and it’s a good insurance policy. Just be sure you also carry a flashlight, a pocketknife and a set of screwdrivers. (Check out more essential tools no DIY mechanic should be without.)

Here’s everything you’ll need to carry out DIY heater hose repair: 

  • Heater hose coupling
  • Hose clamps
  • Water or coolant
  • 4-in-1 screwdriver
  • Flashlight
  • Rags
  • Pocketknife

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Heater hose repair - lift car hoodPhoto: Shutterstock

Open your hood and let everything cool down


Don’t mess with the radiator cap or other parts just yet! Avoid touching anything until you can do so comfortably as you risk getting a serious burn. You might have to wait as long as 45 minutes before you assess the damage. As the engine cools, look for splits or tears in the hoses. The telltale signs of a blown hose will be coolant splashed over the engine and under the hood. This alone doesn’t mean you have a blown hose, however. It could be a faulty thermostat that caused the radiator cap to release. If the cap has a pressure-release flap that’s released, your engine may have only overheated, but if the cap is intact and you can see a leak in the heater hose, you’ll be able to fix it. Once the engine is cool, remove the radiator cap. Put the cap back on after the fix.

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Car heater hose repair - look for the leakPhoto: FamilyHandyman.com

Look for a leak along the length of your heater hose

Carefully examine the hose from the water pump back to the heater core inlet and outlet near the firewall (the backside of the engine compartment).

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Cut out bad section of car heater hosePhoto: FamilyHandyman.com

Cut out the bad section of hose

The leak may be at a fitting on the water pump or even at the heater core. If this is the case, you won’t need to use the coupling; just cut the bad end off the hose, stretch the hose and reclamp it to the fitting. If the leak is along the hose, cut it at the leak and remove the bad section.

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Heater hose repair - push hose onto couplingPhoto: FamilyHandyman.com

Push the hose firmly onto the coupling

Apply coolant to the coupling as a lubricant. Insert one end and tighten the clamp on it. Then slip the second clamp over the hose and push the other end of the coupling into the hose.

Find how to replace a coolant hose with these expert instructions.

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Heater hose repair - tighten clampsPhoto: FamilyHandyman.com

Tighten the clamps

Make sure the hose is slipped onto the coupling and tighten both clamps. Don’t cowboy the hoses; they may be fragile and in need of replacement. Add water to your reservoir or radiator, or drive (no longer than 10 minutes!) to the nearest place you can get coolant. This fix isn’t permanent, so make an appointment to have your hoses and coolant checked before your next scheduled maintenance appointment.

Check out 100 more car repairs you can do on your own.

Originally Published on The Family Handyman