The fan clutch is responsible for pushing radiator fluid through the water pump, which keeps the engine cool. Specialty tools are needed to remove the fan clutch from the water pump. A malfunctioning fan clutch can cause the engine to overheat because of poorly circulating radiator fluid. Although this installation is a challenging process, following the instructions that come from a repair manual such as the Haynes manual can make the process a lot easier.
Remove the intake baffle by removing the bolts that attach it to the radiator support. On 2002 model Trailblazers you will also have to remove 4 push pins that hold the baffle to the support.
Disconnect the transmission lines from the support bracket by removing the hose clamps. Depending on the year of the vehicle, some clamps can be removed by hand and others will need to be removed with a Phillips-head screwdriver.
Disconnect the clutch electrical connections with your hand. This connection is located next to the radiator fan shroud.
Drain at least 1 gallon of fluid from the radiator. This will prevent any spillage in the upcoming steps. Use needle-nose pliers to loosen the butterfly drain plug on the bottom of the radiator and let the fluid drain into a bucket. With the fluid drained, tighten the drain plug with the needle-nose pliers.
Remove the upper radiator hose and wipe up any excess fluid that might have spilled. Use the Phillips-head screwdriver and remove the hose clamps from each end of the hose.
Remove the fan clutch from the water pump housing using a fan clutch wrench. This is a specialty tool that can be rented or purchased from any automotive store.
Remove the fan clutch from the water pump housing. With some models you may have to remove the radiator fan shroud. If you must remove the shroud, unbolt the shroud from the radiator by using a socket on the four bolts. They should be 1/2-inch bolts; a bolt is located in each corner of the shroud.
Remove the fan from the fan clutch by removing the 4 bolts on the backside of the fan. The bolts are 3/8-inch bolts.
Install the fan to the new fan clutch and tighten down the bolts with the ratchet and a 5/8 socket. Note that the 5/8 nut may also be a 11/16 nut.
Install the fan clutch to the water pump housing and tighten down the clutch with the fan clutch wrench. Reinstall the fan shroud and tighten down the 4 bolts that hold it in place. Reattach the upper radiator hose and tighten down the hose clamps with the Phillips-head screwdriver.
Reinstall the transmission cooler lines and reattach the electrical connection to the fan clutch. Refill the radiator fluid and hand-tighten the radiator cap.
Check all the connections and make sure that all the pieces have been reinstalled. Make sure that the fan clutch is tightened down to the specifications in the manual, and that all the hose clamps are tight.
