I bought a 2001 Chevy Malibu a few days ago the guy I bought it from said he just replaced the battery and it drove fine for a day or 2 and then I took it on freeway at about 70mph for a few minutes and it started overheating I drained out all the coolant and water and put fresh coolant and water and it still overheated that night the same night I noticed the rpm gauge wasn’t moving the way it should I’d be going 35 mph and the rpm gauge would stay at 0 and then jump to about 2 and fluctuate and I also noticed that the lights and power go weak for a second and the steering gets real hard for a second when I stop at stoplights like it wants to turn off and I fixed the overheating by replacing the thermostat right after that I drove on the freeway about 70 mph and made it home with no overheating but the power would still go dim at stop lights as I had my foot on the break when I got home before I even parked my car it turned off and so I tried turning it on and it had no crank and the rpm mph gas and thermostat gauge all go about half way up and go back down as I turn the key and at one point the gauges went all the way up and nothing changed when I tried jumpstarting and I also noticed that everything was turning off when I step on the breaks even by just having the key in the ignition all the gauges jump a little so I need some help finding out what the problem is
I had a 2002 Malibu with very similar symptoms. It turned out to be a failing ignition switch.
Also, keep a close eye on your coolant level. If you have a 3.1 liter V6 they were notorious for leaky intake manifold gaskets.