Checking and Changing Hoses

Tools, Parts & Products

non-hardening gasket sealer
adjustable pliers
slip-joint pliers
repair manual

An important part of a maintenance check should be inspecting water hoses for signs of deterioration. Overlooking a bad upper or lower radiator hose or heater hose can lead to overheating problems.

The first thing to check for is leaking hoses. If you see antifreeze anywhere, a hose is seeping or leaking and must be replaced immediately. Hoses that prove to be excessively hard, brittle, soft, mushy or swollen must also be changed. Squeeze and bend the hoses to look for cracks in the middle of the hose. Cracks at the ends are usually quite obvious. If in doubt about the condition of any hose, replace it now to avoid any future problems (especially in hot weather).

Obtain the correct hoses for your car at an auto parts store, or check websites of hose manufacturers like Gates or try Rock Auto Parts. It may be cheaper to buy the hose locally to save shipping, but these websites can help determine proper part numbers. Also, it seems like Rock Auto has worked out many cross-applications to determine which current hoses fit specific older cars.

If you need to replace heater hoses, measure both the length and inside diameter of the old hose. Heater hose comes in ½-, 8- or ¾-inch sizes and is usually sold by the foot. On some cars, the inlet hose could be a different size than the outlet hose, so don’t measure only one and assume they’re the same.

You should also plan on replacing old hose clamps, which tend to weaken and corrode with age. If your car is restored and you want an authentic look under the hood, look for hobby suppliers who sell original equipment reproductions. Whatever style of clamp you purchase, stay away from cheap look-a-like clamps, as many don’t work as well as name-brand hoses.

To replace a hose, let the car cool completely so you don’t get scalded by hot antifreeze. Place a drain pan or bucket under the radiator. Then open the petcock or valve near the bottom of the radiator. If you’re going to install new coolant, dispose of the old coolant immediately, as it’s poisonous. Keep pets away from the old coolant; they tend to like its sweet taste.

Remove the hose clamps from your old hose with pliers or a screwdriver, depending on the style of clamp. Then twist and pull the old hose loose. If it won’t come off easily, you may have to split the old hose with a knife or blade cutter. Sometimes a hose will pull off better with pliers than by hand. Then remove the hose and carefully scrape the metal (or plastic) hose fittings clean. Before installing a new hose, apply a small amount of non-hardening gasket sealer to the fitting only. Don’t put sealer inside the hose, as any excess amount could get into and clog the cooling system. The sealer will also help the hose slide onto the fitting.

Slide the new clamps onto your new hose before you slide the hose onto the fittings. Make sure the hose ends slide over the fittings far enough to allow the hose clamps to grab the fitting and make a tight seal. Now move the hose clamps near the ends of the hose and tighten the clamps. Fill the radiator with coolant and start the car to check the cooling system for any leaks. Recheck the coolant level after the engine has achieved its proper operating temperature.

John “Gunner” Gunnell is the automotive books editor at Krause Publications in Iola, Wis., and former editor of Old Cars Weekly and Old Cars Price Guide.

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