How to Change a Water Pump on a 3.9 V6 Chevrolet Engine
The 3900 V6 engine is used is several of the company’s vehicles, from sedans to vans. This tutorial is specific to the 2007 Chevy Uplander van, but many of the steps will apply to another vehicle.
The job takes about three hours and an intermediately skilled mechanic should not have any problems doing the work. I had not worked on a vehicle in nearly 20 years, and I accomplished the task with only one issue—the serpentine belt—and I’ll explain in the steps below how to avoid the problem I had.
Step 1: Make sure the water pump needs to be replaced. This may sound overly simplistic, but look for a couple of clues.
The first one is your engine will overheat (don’t let it get too hot as it will ‘blow’ the engine). In my situation, the vehicle would run about 10 minutes, and then start getting hot.
Look for leaks around the water pump. The water pump is located just above – and to the right – of the crankshaft pulley. It is above – and to the left – of the air conditioner compressor.
Step 2: Remove all the items blocking access to the water pump. In the 2007 Uplander this is three or four items. The first is the fuse box. This is removed by taking off the cover to expose two small nuts that attach the box to the fender wall. Once those are removed the fuse box can be positioned out of the way. The next item to remove is the cross bar. Two bolts connect it to the front of the engine compartment and a third bolt secures it to the fender wall area. Lastly remove the battery. This will give you enough room to maneuver, but if you want a little more access, you can also detach the windshield wiper fluid container.
Step 3: Loosen the four bolts securing the pulley to the water pump. Leave one bolt in until after the serpentine belt is removed.
Step 4: Remove the serpentine belt. This is done by placing a 3/8 inch racket or breaker bar in the tension pulley. If you are standing in front of the vehicle, it will be about a foot behind the craft shaft pulley—parallel to the water pump. It is a tight fit. Once the ratchet is attached to the pulley, pull it clockwise (toward you) to loosen the belt. When you slide the belt off, do it slowly, to keep it wound around all the other pulleys. It will save you time in the long run.
Step 5: Remove the final bolt from the pulley cover to remove it from the water pump. If the pulley sticks, use a long-handled screwdriver or a pry bar to force it off.
Step 6: Remove the five bolts that secure the water pump to the engine block.
Step 7: Remove the old water pump. Clean the surface where the gasket seals. You may also want to flush out the cavity to remove any build up.
Step 8: Attach the new pump, making sure the new gasket is aligned correctly. Finger tighten all the bolts then stagger the tightening process with a ratchet to ensure the gasket seals. Do not overtighten.
Step 9: Reattach the pulley. Tighten the bolts to about 5 PSI. Again, do not overtighten.
Step 10: Reattach the serpentine belt. This is the only place I ran into trouble because I let the belt slip off and had to figure out how to rewind it. The basic rule of thumb is smooth pulleys get the backside of the belt while grooved pulleys get the front (ribbed) side. If the belt falls off, one trick I learned the hard way is attach the belt from behind on the pulley located directly below the alternator. If you wind it from the front, it will not work.
Step 11: Install the battery to start the engine and to check for leaks.
Step 12: Add anti-freeze (to check for leaks) and let the engine run for 15-20 minutes. Watch your temperature gauge during this process. If it continues to overheat (as mine did, see below), then you also have another issue – possibly a bad thermostat or a blockage in the coolant system.
Step 13: If there are no leaks, and the engine is not overheating, reattach the crossbar and the fuse box.
Step 14: Ensure the antifreeze level is correct and test drive the vehicle at road speed to make sure all is working smoothly.
Step 15: After the engine has cooled (possibly next day), double check anti-freeze levels to make sure coolant level is correct.
If Your Engine Still Overheats: Removing Air From the Coolant System
After I installed the water pump, the engine still overheated. This was due to air being trapped in the coolant system. You can solve this a couple of ways. One is fill the overfill tank and let the engine set overnight. The antifreeze will ‘seep’ into the system forcing the air out. Another approach is to fill the radiator, leave the cap off and let the engine run, adding antifreeze as needed. I ended up doing both approaches since I changed out the thermostat and flushed the heater lines. Both methods worked for me.