How to Install a 4.6 Northstar Water Pump

The 4.6l Northstar engine drives the water pump with a small belt on a pulley attached to the camshaft on the back of the cylinder head. General Motors introduced the Northstar engine in Cadillac's in 1993 and designed it to survive cooling system problems that cause overheating, such as a water-pump failure. When the engine starts to overheat, the Northstar's computer limits the vehicles speed and uses an air-cooling strategy of alternating which cylinder bank is firing to limit damage until the Northstar's cooling system is repaired.

Instructions

Disconnect the negative battery cable from the battery for safety while replacing the Northstar 4.6-liter engine's water pump.

Open the radiator cap. Open the radiator drain on the driver's side lower corner of the radiator and drain the coolant into the coolant drain bucket.

Remove the air cleaner cover screws, using the flathead screwdriver. Pry the air-intake hose from the throttle bore. Remove the air-cleaner cover and air-intake hose assembly from the vehicle.

Remove the black, steel water-pump belt guard using a 10mm wrench to remove the retaining bolts. The water-pump assembly is located at the end of the cylinder head, where the engine and transmission bolt together. The oil dipstick tube is bolted to the water-pump housing.

Pry the water-pump belt tensioner up and remove the water-pump drive belt.

Squeeze the hose clamp on the lower radiator hose with the pinch-clamp pliers and remove the hose. Repeat for the smaller bypass hose. Both hoses attach to a cover bolted to the water-pump assembly. The cover also houses the thermostat.

Remove the 10mm bolts retaining the water-pump cover to the housing and remove the water-pump cover.

Install the water-pump-removal tool. The tool consists of two parts: a toothed cup and a retaining bar. Insert the cup over the water pump impeller. Engage the teeth with the water-pump retaining tabs at the back of the housing. Install the retaining bar to hold the cup in place. Install two of the 10mm water-pump retaining bolts finger tight. Insert a 1/2-inch-drive ratchet into the square hole of the tool.

Turn the 1/2-inch-drive ratchet clockwise. Remove the water-pump-removal tool and the water pump from the water-pump housing.

Install a new O-ring on the new water pump. Lubricate the O-ring and the mounting ears of the water pump with silicone grease. Insert the water pump into the housing.

Mount the Northstar water-pump tool over the water pump. Turn the ratchet counterclockwise until the water pump retaining tabs are fully engaged with the water pump housing. Remove the water pump tool.

Install the water-pump cover. Reinstall the lower radiator hose and coolant bypass hose.

Reinstall the belt. Pry the belt tensioner up for slack to allow the belt installation. Seat the belt fully into the grooves of the camshaft pulley, water pump pulley and tensioner pulley before releasing the tensioner.

Reinstall the belt guard and air-cleaner assembly.

Close the radiator drain. Refill the cooling system with antifreeze.

Reconnect the negative battery cable.

Start the vehicle and allow it to reach operating temperature. Check for leaks and top off the cooling system reservoir bottle to the "Full Hot" mark.