Let It Flow

4 years ago How-To

Water pump


The water pump is the heart of the cooling system for any engine. It works to pump coolant through the engine in order to remove the heat. It also pumps coolant into the radiator to remove heat throughout the engine. This component is as critical to the cooling system as the oil pump is to the lubrication system. Unfortunately, the water pump operates in a slightly harsher environment than its lubricating counterpart, which may result in water pump issues over time and miles of operation.

Aside from material (many water pumps now use aluminum castings as opposed to cast iron), not much has changed with water pumps over the years. Basically, it’s an impeller inside of a housing that circulates the coolant through the engine. In popular inline 4-cylinder overhead cam (OHC) engines, the water pump is driven by the timing belt, while on V-style engines, it is driven by a V-belt via a pulley mounted on the pump shaft flange.

HEMI engine water pumpWATER PUMP BASICS

A centrifugal water pump (1), such as the one used on HEMI® V8 engines (see Figure 1), circulates coolant through water jackets, passages, intake manifold, radiator core, cooling system hoses and the heater core (this allows the passenger compartment to be heated). The pump is driven from the engine crankshaft by a single serpentine main drive belt.

The impeller (2) is pressed onto the rear of the shaft and it rotates on bearings pressed into the housing (3). The housing has two small holes to allow seepage to escape. The water pump seals are lubricated by the antifreeze in the coolant, eliminating the need for additional lubrication. The water pump is mounted directly to the timing chain cover. It is equipped with a non-serviceable integral pulley.


If the coolant temperature rises above normal, a problem with the water pump may become evident. While the water pump might not necessarily be the source of the problem, it’s not a bad place to look first. So, start by checking for cracks in the housing, and then look for coolant leaks.

When a water pump fails, it is likely that the shaft seal is bad. If the shaft seal is bad, a trail of dried, thick deposit of glycol on the pump body is a tell tale sign. When the leak is severe, the coolant will find its way onto the ground under the vehicle. When coolant is found on the ground, don’t assume that the water pump is bad. Check to make sure. The coolant leak might be from a coolant hose or a hose connection.

If the primary weep passage is plugged, coolant might leak through the secondary weep hole and collect in the valley of the engine. This coolant will eventually run out the backside of the engine. A leak of this type might give a false indication that an engine block core plug might be leaking on the backside of the engine. If this condition is found, clean the primary weep passage of debris.

Note: It is normal for the water pump to weep a small amount of coolant from the primary weep hole; this will look like a black stain at the weep hole; this is not a sign of pump failure; the trail of thick deposits is the sign of seal failure which requires pump replacement.

Other types of water pump failure are (1) the impeller rubbing on the inside of the cylinder block and (2) an excessively loose or rough turning bearing. Both of these conditions are a sign of failure that requires pump replacement.


Water pump replacement is more straightforward on the HEMI V8 engine due to the fact that this particular engine is not transverse mounted, as is the case with many other models with 4- and 6-cylinder engines. As a result, access to the water pump is less cluttered, making the replacement procedure much easier than it would be on transverse-mounted engines.Close up of HEMI engine water pump

While the replacement procedure is straightforward, several components must be removed in order to gain access to the water pump. First, remove the air cleaner body, the resonator-mounting bracket and the cooling fan assembly. Next, drain the cooling system and then remove the serpentine belt. Remove the heater tube bolt and disconnect the engine coolant temperature (ECT) sensor wire harness connector.

Refer to Figure 2; remove the upper radiator hose from the thermostat housing (1) and move to the side. Remove the bolt and the idler pulley (5). Next, remove the belt tensioner assembly (4). Remove the lower radiator hose from the water pump and move it out of the way. Remove the upper stud bolt (2) and the water pump mounting bolts (6). Carefully remove the water pump (3) from the cover while removing the metal bypass tube.

Before installing the new water pump, clean and inspect the mating surfaces of the timing chain cover. Again, refer to Figure 2. Install the new water pump (3) and tighten the bolts (6) to the proper torque specification. For our subject vehicle, a 2014 Dodge Challenger, the correct torque for the water pump mounting bolts is 18 ft.-lbs. Install the upper stud bolt (2).

Next, install the lower radiator hose to the water pump, then install the upper radiator hose to the thermostat housing (1). Install the belt tensioner assembly (4) and tighten that bolt to 30 ft.-lbs. Install the idler pulley (5) and tighten that bolt to 21 ft.-lbs. Connect the ECT wire harness connector. Then, using a new O-ring, install the heater tube.

To complete the installation, install the serpentine belt, the cooling fan assembly and the air cleaner body. Evacuate the air from the cooling system and refill it with the proper coolant. Start the engine and bring it to normal operating temperature. Check for any cooling system leaks.



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