How to Replace the Heater Hoses in a GMC Sierra

Heater hoses are an often overlooked, but integral part of your GMC Sierra's cooling system. Due to their rubber composite composition, they're highly susceptible to splitting, cracking and bulging. If you don't replace the heater hoses when they first start showing signs of wear, they will eventually leak and can cause the cooling system to fail.

Things You'll Need

• Bucket
• Sealable container
• Screwdriver or pliers
• Knife
• Gasket sealer
• Heater hoses
• Hose clamps (optional)
• Coolant

Instructions

1. Position a bucket with a capacity of at least two gallons underneath the radiator and directly below the drain plug. On the GMC Sierra, the drain plug is usually on the bottom passenger side of the radiator.

2. Open the drain plug and allow the cooling system to drain completely. Once complete, pour the old coolant into a sealable container for proper disposal.

3. Loosen the hose clamps and pull them back from their connections to the engine and the heater core. You'll need either a screwdriver or pliers, depending on the type of hose clamp. The heater core is behind the engine and up underneath the windshield. The heater hoses dead end at the firewall between the engine and passenger side of the GMC Sierra.

4. Make a few lengthwise slices on the heater hose with a knife. You should never try to pull or twist the hose off without these cuts, as that can damage the heater core.

5. Remove the old heater hoses and scrape away any leftover debris on the fittings. Next, place a bit of gasket sealer on the fitting but don't place any on the inside or outside of the new hoses.

6. Place the hose clamps on the new heater hoses and slide them into place over the fittings. You may want to replace the clamps as well, as they can wear down over time and also cause leaks. Be certain there's enough hose on the fittings to secure the clamps.

7. Tighten the hose clamps, refill the radiator with fresh coolant and start the engine of the GMC Sierra. Let it run for about 15 minutes to check for any leaks from the new heater hoses.

Tips & Warnings

• Some heater hoses vary in size. Therefore, you should measure the inner circumference of the new hose and compare it to that of the old hose.

• Never open a hot or warm radiator, as the internal pressure can cause an eruption and burn anyone in the area.

• Be very careful with coolant, as it's extremely toxic to pets and people alike.