My 2014 F150 started leaking coolant and I determined it was the water pump. This being my first time to swap out a water pump, I watched YouTube videos, reviewed the Haynes manual, and read online forums.

When the parts arrived from RockAuto, I got to work gaining access to the water pump and proceeded to remove the 4 mounting bolts. Next, I grabbed the pump and tried to pull it out. It barely budged, so I sprayed penetrating oil on the seal thinking that was causing it to stick and it finally started to come out at the top end. The bottom end remained stuck, which was very frustrating. So I grabbed a hammer and proceeded to beat the neck of the pump but it still wouldn’t come out.

At one point, my wife asked if I removed all the bolts. I hastily pointed out that all four bolts had been removed and went back to swinging the hammer.

After taking a much needed break, I came back to the truck and happened to look again at the bottom right side of the pump from a slightly different angle. I could see the head of a bolt! I removed that bolt and the pump came out easily. I soon realized there are two identical looking bolts located side by side. I had mistakenly removed the wrong bolt in the beginning.

Lesson learned is to verify all mounting bolts are truly removed before hitting anything with a hammer. More importantly, it’s okay for your significant other to ask questions. It can save you hours of stress and frustration.

Adam in Texas

Stricter emissions/fuel economy regulations, systems that stop/start engines in traffic, customers who expect vehicle interiors to warm up quickly and other factors led to modern engines that reach operating temperature faster and tightly maintain that temperature. A switch to electric water pumps was logical because they make it easier to instantly vary the flow of coolant by changing the speed and/or duty cycle of the water pump's electric motor.

What may be surprising is that some mechanical, belt-driven water pumps are computer controlled as well. These variable (switchable) water pumps will have a pulley for the serpentine belt but will also have an electrical connector or vacuum hose port. The pump's impeller spins continuously, but when the computer wants to reduce coolant flow (increase engine temperature), it activates a mechanical door (shroud, shutter...) that essentially walls off the impeller. The spinning but now isolated impeller just churns the surrounding stagnant coolant like an egg beater.

Here are some of the mechanisms a switchable water pump may use to open and close its internal door:

• Electromagnetic clutch that operates similarly to the radiator fan clutches that have been around for more than half a century. When temperature rises to a certain level, a thermal coil spring engages the clutch on a belt-driven radiator fan. Similarly, the computer switches a solenoid on/off to operate the water pump's clutch.
• An electrohydraulic actuator/valve routes pressurized coolant through the correct passageway to move the pump's internal door or shroud.
• Vacuum directly sucks the door mechanism into position, or a vacuum diaphragm moves the door's open/close linkage.

Problems arise when a variable water pump's internal mechanical door wears out and intermittently or permanently blocks coolant flow to/from the impeller. The computer sees the engine is overheating but may not know the pump's internal door is stuck and not responding to the electric or vacuum switch. The computer may generate general cooling system trouble codes, it may run the electric radiator fan(s) continuously, it may initiate some type of limp-in mode... The driver should notice temperature warning lights and/or a high temperature gauge reading.

Both the computer and car owner may have a harder time diagnosing the problem if the electric switch or vacuum diaphragm in the water pump fails in such a way that coolant begins to leak into a wiring harness or gets sucked up into a vacuum reservoir or some other piece of seemingly unrelated vacuum plumbing. Disappearing coolant and/or coolant showing up in wiring or vacuum lines could be a switchable water pump problem.

Watch for serpentine belt-driven water pumps that have vacuum fittings or electrical connectors on them. These pumps are most common on European brands (Audi, Jaguar, Mercedes- Benz, Volkswagen...). See the water pump(s) your specific vehicle uses under "Cooling System" in the RockAuto.com catalog.

Tom Taylor,
RockAuto.com

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