The following information will guide you through the procedure of changing the water pump on the Buick 3800 engine. This information can also be found on Padgett's website.

The main cause of water pump failure is a defective front seal. However, it is possible for the pump to start making a rattling noise due to a bad bearing before the seal fails. If you hear an unexplained rattling at the front of the engine check the pump by removing the belt and moving the water pump pulley from side to side. If you feel excessive movement, replace the pump.



Water pumps, (Bosch 97134), for the 3800 engine are so inexpensive there is no reason to use a rebuilt pump.

Tools Needed:

• Breaker bar & 18mm socket (to take tension off the belt)
• Rachet, 4" extension, 10mm & 13mm sockets
• Screwdriver (to remove the hose clamps on the bypass hose if needed)
• Soft Mallet (might be needed to break the pump loose)
• Torque Wrench (recommended but optional)

It is not necessary to remove the radiator hoses in order to change the water pump.

1. Drain the cooling system. It should be drained down to beneath the bottom of the water pump. If not drained it will come out when the pump is removed.

2. Remove the bolts from the belt pulley. There are four screws (10 mm socket) that hold the pulley wheel on the water pump hub. This is easiest done with the serpentine belt helping hold the pulley from turning.

3. Remove the bolts  holding the water pump. There are four screws that require a 10 mm socket (4" extension is needed for socket wrench to clear other sharp items), three on top and one at bottom center. These are followed by four larger screws that take a 13 mm socket, two at either end.These may be gummed up and come out tight.

4. Remove the pump from the block. When all eight bolts have been removed, all that is holding the old pump on is the gasket. Unfortunately some sealers are a lot like glue. In this case a few sharp raps on the hub with a soft mallet should pop it loose.

Do not try to pry between the timing cover and the pump because the cover is soft aluminum and scores easily. Remember the guide pins allow it to be removed straight out only.

5. Prepare the block. Getting the block surface really clean by using an assortment of scrapers and Emory cloth is one of the most important steps in this process. This will take a considerable amount iof time if the gasket is stuck to the block with some types of sealer.

• Use chisel scrapers to remove the gasket material paying particular attention to the area around the two guide pins. Take care not to gouge nicks in the serface.
   
• Use razor blade scrapers to remove all remaining traces of gasket or sealant from the timing cover.
   
• Repeat and continue until there is nowhere on the mating surface that you can catch a fingernail.
   
• Once scraped completely smooth, use Emory cloth to create a uniform surface.
   
• Wash surface with solvent to remove all particles
   
• Optional - Depending on how the bolts felt coming out you might need to run a tap through the 8 threaded holes. Clean taps after each hole.

6. Check the bypass hose. The photograph below shows a small bypass hose that runs between the intake manifold and the water pump housing. It should be replaced while the pump is off if needed. It is very hard to replace the hose with the water pump installed.

While you have the coolant drained you should also check the upper radiator hose and the lower radiator hose. It could save you some trouble in the future.

Reassemble

1. Prepare the gasket.  Since a gasket should have been included with the pump, that is what I use (do not care for "make your own" silicone) but first I apply a thin layer of axle grease to the whole gasket. This has two purposes: a decade hence when a new pump may be needed, the old one will come off easily and cleanly. Also the grease will help the gasket to stick on the block while attaching the water pump.

2. Put the gasket in place. Use the guide pins as, well, guides. (see photo above) Have screws handy and place new water pump in place over gasket and guide pins. I begin with two of the larger screws, one in each end, just finger tight to hold the pump in place. Next screw in the other six finger tight.

3. Snug down the screws. First the smaller screws and then the larger ones. Then tighten alternatively with a 1/4" driver. Final torque spec is 8 lb-ft for four smaller screws and 22 lb-ft for four large ones. Hub is 10 lb-ft. Do not play Godzilla (and if surface is properly prepared, you will not need to.)

4. Install the hub pulley. Snug the screws down but don't try to tighten them completely,

5. Install the serpentine belt. There should be a sticker on the hood showing the proper routing.

6. Tighten the hub pulley screws They should be torqued to 10 lb-ft.  Don't over tighten.


7. Refill the radiator and run at idle, revving a couple of times to 2500ish rpm to burp the system. Refill again, it should need about a gallon to five quarts. Once the radiator is full, replace the cap (to build pressure), let the engine run up to operating temperature, and check for leaks (fixing one thing may expose others).

If no leaks are found then all that remains is cleanup and putting tools away.