How to Test a Vehicle's Water Pump
- 1). Listen for squealing, chirping, ringing or humming coming from your water pump. If you hear a noise but can't tell where it's coming from, then take the tip of a very long screwdriver and press it firmly onto the water pump. Press your ear firmly to the rounded end of the handle as though you were trying to shove it into your head. The solid screwdriver will conduct any noise in the pump directly into your skull and inner ear, allowing you to precisely pinpoint the source of the noise.
- 2). Open the radiator cap, start the engine and bring it up to operating temperature. Look down into the open radiator cap at the water in the reservoir, and at the upper radiator hose input, if possible. After the engine warms up, you should see water steadily flooding into the radiator, not trickling, especially when you rev the engine up a little. Trickling or no water flow might also indicate a bad thermostat, but either way, something is going wrong.
- 3). Rev the engine up a little and watch for steam coming out of the upper radiator hose or radiator cap without an accompanying rush of water. If the thermostat is stuck halfway open, the water pump will build up pressure on the bottom of the thermostat and try to force water through it. That water won't go through, but an increase in downstream pressure can force the pressurized water stream to rapidly decompress on the radiator side of the thermostat. This decompression can create a gout of steam -- something a bad water pump won't do. So, steam equals bad thermostat.
- 4). Determine whether or not you have a leak around the water pump, since this is where failures usually start. Clean the area around the water-pump-to-block gasket and the bottom of the shaft with dish detergent and water, then thoroughly dry it off with compressed air or a towel. Fill your hand with baby powder and toss it on, under and around the water pump. Some of it will soak into existing water or grease, but keep applying powder until you have a dry, uniform dusting. Start the engine and allow it to idle and get up to temperature. Leaks may only occur under pressure, so heat is essential here.
- 5). Watch around the pump for streaks or dark spots in the powder. If your pump is leaking, then the powder will tell the tale. If, after 15 to 20 minutes of idling, you see no streaks or other obvious signs of leakage, then the leak -- if any -- is coming from somewhere else. That doesn't mean your water pump is fine -- just that it's not leaking. Turn the engine off, hose it clean and give it some time to cool down and dry off. Don't hit the hot exhaust manifolds or electronic equipment with water.
- 6). Remove the belt and check the water pump shaft. Grasp the pulley with both hands, if possible, and try to wiggle it back and forth, up and down and in and out. Any used water pump will exhibit a bit of shaft play, but if yours move more than 1/16-inch in any direction then it's time for a new pump.
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