My main top water hose burst. I replaced it. Car ran hot. Replaced the thermastat, coolant sensor, and 12 volt relay fuses for primary and secondary fans. Still ran hot. Fans not coming on. I tested fans in service mode by paper clip to F and G in the diagnostic scan box. Fans came on, so no blowed motors. Got desperate, so ran a toggle switch to primary fan, so fan would run while I drive. Still, when the car gets hot, after about 5 miles of regular driving, the car huckabucks, and cuts off at slow downs and stops. Really bad in the middle of light intersections. Can anyone help?
The head gasket may be leaking, which would cause overheating even if the fans were running properly. It would also allow coolant into the cylinders and possibly cause the rough running and stalling if enough coolant is leaking into the cylinders.
Since a leaking head gasket is a major problem, that is the first thing you should have a mechanic check for. There are several ways to test for a leaking head gasket and a competent mechanic should be able to do it. You can also do a simple check yourself by removing the radiator cap when cold, then starting the engine and looking for bubbles in the coolant. Bubbles mean the head gasket is leaking. Have someone rev the engine and see if it causes more bubbles.
You can also buy a test kit that will chemically test the coolant for acidity caused by a head gasket leak.
If the head gasket isn’t leaking, then you can do more troubleshooting, but if it is, nothing else will help.
Considering this is a GM 3.1 V6, I’d say failed intake gaskets are more likely than failed head gaskets
@db4690 is probably correct. Here’s more on the intake gasket issue: