Is changing the water pump on a 98 malibu 4cyl like a 7hr job?

replace thermostat did bleed coolant system check coolant level.because if not engine could have overheated and blowed headgaskets warp or cracked the heads check engine compression.sound like engine got too hot.

When you change a water pump on a vehicle with a timing belt
you change the tensioners & idler pulleys as well

Using the wrong oil & not changing it every 4000 miles or less
causes the tensioners to stick

If your engine is running fine with no miss in it possibilities could be radiator fan or water pump if the radiator fan is working fine it could be the water pump. I have seen a water pump after removing it where the fins on the pump were completely worn out causing the overheating.Let me know how this turns out for you thanks.

Have to look at the new pump,some are a splined shaft that just slides on to the gear ,those are fairly easy,if the new pump has a gear on the end the whole front cover and timing chain has to come off ,big job.

Check that the Negative ground cable was hooked back up properly.
Sounds like a bad connection.

Are you sure it's the oil pump, Most of the time it's the oil sensor that has gone bad. Just trying to save you lot's of job since the oil pump is at the bottom of the engine in the oil pan. You can check by having the engine running and looking down the hole where the oil filler cap goes. Rev the engine up a bit and you should see oil splashing around which means your oil pump is working. Your oil pressure is created by the crank shaft. Good luck 

you have too change the whole assembly
pull the wheel pull the callipilar pull the callipliar mount pull the rotor pull the half shaft nut then take the three bolts out of the hub assembly and pull it less than hour job !!!!

water pump is no big deal ,thermostat that a bigger job there not mush room to work but why the timming chain were i work the owner got a taxi fleet all maliby from 200 to 2003 i never say in my mechanical career or needed to change a timing chain on a malibe those years some of malibu has close to 600,000km change a lot of intake gasket but timing chain never please tell why the shop whant to change the timing chain do you now the shop good thanks pierre

Hi....
On your 2004 Santa Fe.
The water pump is not driven by the Timing belt.
Is not stricttly nessesary to replace togheter. they are individual.
But I recomend replace the timing belt when you replace the water pump. Because for get axces to the water pump,
you need to remove all the Timing covers.
Is just a few more minutes to remove the Timing belt.
Inspect the Engine seals, cam and crank Replace if need.
My PC show me a 2.4L 4cyl. for 2004 santa fe.

Ok.. The labor for that job Removing the Timing belt and water Pump ...IS:
2.8 hours. just the water pump 2.4 hours.

OK.. I hope this help on your question...
Thank you for use fixya..

2.4 timing chain