I have a coolant leak and I belive I need to replace the water pump, A 2004 GMC P-up 4.3 V-8

If coolant is leaking from the water pump, it's a gasket or pump seal that's bad.

The water pump is in front of your motor. If the coolant is leaking from under the water pump, then the gaskets on your pump need to be replaced. Depending on how many miles you have on your vehicle, you're better off replacing the whole pump, plus the belts and thermostat. Yes, new gaskets come with the pump.

Please get a Coolant pressure test done which will expose the real leak.

I’m happy to assist further over the phone at https://www.6ya.com/expert/uttamjeet_2f3adc18600f8ede

Check for water laying in the heater core box.Most likely the heater core is leaking.

I was going to say water pump but no block the water inlet to throttle body and let run a while can you smell a sweet smell or steam comming from your tail pipe Next is a die test you can do . Put the die in your rad and go for a 5 mile ride now use a cheep black lite $3.00 at lowes the leak will show up. good luck CJ

It Depends on which engine you have, this is how it goes for both. I use a little RTV with a new ring as well.

THERMOSTAT REPLACEMENT (4.2L ENGINE)
Removal Procedure
1. Remove the necessary coolant from the radiator.
2. Remove the generator.
3. Loosen the outlet hose clamp at the thermostat housing. Remove the outlet hose from the thermostat housing.
4. Remove the thermostat housing bolts.
5. Remove the thermostat housing from the engine block.
6. Clean all of the surfaces of the thermostat housing.
7. Clean the sealing surface of the engine block.
Installation Procedure
1. Install the thermostat housing to the engine block.
2. Install the thermostat housing bolts.
Tighten: Tighten the bolts to 10 N.m (89 lb in).
3. Lubricate the inner diameter of the radiator hose with engine coolant.
4. Install the outlet hose to the thermostat housing. Secure the hose with the clamp.
5. Install the generator.
6. Fill the cooling system with specified coolant and concentration. Follow the correct cooling systen bleed procedure for your engine.
7. Inspect all sealing surfaces for leaks after starting the engine.
THERMOSTAT REPLACEMENT (5.3L ENGINE)
1. Drain Radiator and remove the radiator outlet hose.
2. Remove the water pump inlet bolts.
3. Remove the water pump inlet and thermostat from the water pump.
Installation Procedure
IMPORTANT: The thermostat is not serviceable separately. The water pump inlet and thermostat must be replaced as an assembly.
1. Install the thermostat and thermostat housing to the water pump.
2. Install the thermostat housing bolts.15 N.m
3. Install the radiator outlet hose.
4. Fill the cooling system with specified coolant and concentration. Follow the correct cooling systen bleed procedure for your engine.
5. Inspect all sealing surfaces for leaks after starting the engine.

Check the radiator and hoses for leaks. Also, look at the water pump and see if any coolant is leaking out of the vent or "weep" hole. If coolant is leaking from the weep hole, the water pump is defective and will need replaced. When checking hoses, look for cracks and leaks, especially around the hose clamps. Hope this helped and best wishes.

I belive they didn't reset the oil light timer. I belive the sequence is 1. key on (not acc with engine off)
2. step on the brake pedal 5 times within 10 seconds. 3. key off. 4. start car. 5. check if the light went out. you may have to try it a few times to get it.

The coolant is more than likely leaking from the water pump "weep" hole. If you were to remove the water pump pulley you would be able to see the coolant track and weep hole.
The leak is an indicator that the seal and/or bearing is wearing out and the water pump needs to be replaced.
If you have some common tools, time and patience, you would be able to change the pump your self. It requires draining the cooling system, removing accessory brackets and hardware then removing and replacing the water pump.
Good luck, let me know.
Regards,

sounds like intake or water pump