Step by step How To: Changing Water Pump on GP

I found lots of threads of people asking about changing the water pump on the GP, so here's my experience on a 98 Grand Prix GT 3800.

1) Drain the radiator. There are two ways to do this, either use the petcock valve, or remove the bottom hose. The drain plug/petcock valve is on the bottom driver side of the rad, it’s cheap plastic junk, hard to get to, and I broke mine. I recommend removing the bottom hose from the radiator and draining it that way, it’s much safer to do.

If you want to remove the petcock, it has plastic "ears" on it, and you need to turn it 1/4" turn counterclockwise. It will "pop" when you make that turn. Next, you pull it out of the radiator about 1/4" and it will begin draining. I got mine open OK using pliers, but busted the ears off when trying to close it.

2) Loosen the 4 bolts on the water pump pulley. You will remove the pulley and install it on the new pump. Just loosen the bolts 1/4" turn with the belt still on, this will prevent the pulley from turning.

3) Remove serpentine belt. (They should beat the person who designed the plastic petcock with this belt).

4) Remove 4 bolts and the pulley and set aside.

5) Remove two power steering pump bolts (15mm). You must do this because one of the bolts for the water pump is behind the PS pulley, and you can’t remove it without moving the PS pump out of the way. The bolts on the PS pump are in the 12 o’clock and 6 o’clock position. There is a large access hole in the PS pump pulley. Just line it up, slip in a long socket and remove them. Let the PS pump rest on the oil filter housing.

6) Remove water pump. There are 4 large bolts (15mm) and 4 small bolts (3/8") on the water pump. After the bolts are all out, I placed a length of pipe on the water pump and gave it a couple taps with a hammer and it popped right off.

7) Remove old gasket. The tool of choice IMO is a razor blade like you’d use to remove a winshield inspection sticker. Be careful not to score the mating surface. Remove old gasket and dry off surface.

8) Seat the new gasket and water pump in place, install all the bolts.

9) Reinstall the PS pump and tighten bolts.

10) Install pulley on water pump

11) Install serpentine belt.

12) Tighten bolts on water pump pulley if needed

13) Close petcock valve or reattach bottom hose, fill with coolant.

Q.

1. Is it necessary to drain the coolant completely (about 2 gallons)? Can I get by with just 1 gallon via petcock valve?

2. No RTV sealant on water pump gasket?

3. No pulley puller is involved, right?

4. Serpentine belt tool is the only specialized tool.

1. Even when you drain the rad, there will still be coolant that drains out of the engine block when you pull the WP out. I guess it depends on how big of a mess you want to make, and how much coolant you want all over your engine. I just drained it all, and used about 2 gal of water/Dexcool mix to refill.

2. Since I purchased an AC Delco WP with gasket, the gasket came with a thin dry bead of sealant on it already. It seals up nice as is.

3. Correct, no pulley puller needed. Just four bolts to remove/reinstall.

4. Actually, no special tools is needed for the serpentine belt. A 15mm socket is used on the idler pulley to release the tension and remove the belt. I have a 2' length of pipe I put on the ratchet for greater leverage. Piece of cake.

4. Actually, no special tools is needed for the serpentine belt. A 15mm socket is used on the idler pulley to release the tension and remove the belt. I have a 2' length of pipe I put on the ratchet for greater leverage. Piece of cake.

Wouldn't the coolant recovery tank be in the way of your socket and ratchet? My further question is when you do the 2 PS pump bolts, does the coolant tank need to come off? Just undo the 2 tiny bolts on top of strut tower to move the coolant tank out of the way, right? Thanks,

I guess it depends on what year the car is. As an owner of a 97, 98, and 02 GP, there are differences among them. On the 98, nothing was in the way, not even the coolant tank, in fact, it's over on the driver side. My instructions were right on, I left nothing out.

You are right about the variation on diff. model years. I just came back from my car and an hour of looking at the engine...

For my 2001 GT, the coolant recovery tank needs to come off and just unbolt the 2 10mm bolts on the strut brace and lift the tank up. Once the tank is out and the belt is off; replacing PS, WP, or alternator is a breeze.

Another difference between my car vs. yours. My petcock has 1/4 square hole and I must use a 1/4 extension (no socket) ratchet to turn it open/close... I just realize that my radiator cap is leaking (slowly) since I drained & refilled my coolant and reused the cap.