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How to Repair a Car Heater Hose

A heater hose repair kit is great insurance against roadside disaster

car hoseFamily Handyman
A leaking heater hose will stop your car dead in it's tracks, but with a basic repair kit you can fix the hose yourself, even out in the middle of nowhere, and be driving again in an hour.

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Time
An hour or less
Complexity
Beginner
Cost
Less than $20

Emergency heater hose repair

Open your hood and let everything cool down

Don’t mess with the radiator cap or anything yet! Don’t touch anything until you can do so comfortably. You could get a serious burn. You might have to wait as long as 45 minutes. 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.

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 (backside of the engine compartment).

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.

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.

Hose coupling

Hose couplings come in several sizes. Check your hose before buying.

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.

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 vaporizing 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 6 years old, no doubt your radiator and heater hoses have seen better days. Next time you’re in the auto supply store, pick up a kit containing a heater hose coupling like the one shown and a pair of clamps. The kit doesn’t cost much and is a good insurance policy. Just be sure you also carry a flashlight, a pocketknife and a set of screwdrivers (essential tools to always have on board). See what you should do if your car is blowing cold air, too.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you startyoull save time and frustration.

  • 4-in-1 screwdriver
  • Flashlight
  • Rags
You’ll also need a pocketknife

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Heater hose coupling
  • Hose clamps
  • Water or coolant