What could be the reason my Lumina LTZ 98 heats up after a while and stop working?

I really hate giving out bad news. Your 98' Lumina has a 3.1L MPI V6 gen.2. These engines are common for intake manifold gasket leaks. I will try to explain how I came to this diagnoses.

First off, it runs good cold. As the engine temp. increases the metals expand and the gaskets are suppose to compensate for that expansion, and as coolant temps increase so does the pressure. When the intake manifold gasket goes bad it allows coolant to be drawn it the cylinders and burnt. This may not be enough to trigger a check engine light, but as coolant is taken away, it is replaced with air. This air gets trapped in the system and usually ends up around the thermostat. The thermostat, coolant temp. sensor, and coolant fan switch are all located in this general area. These components need to be submerged in fluid to operate properly. As the engine is heating up and with no gauge to monitor temps., the cylinder temperatures will reach a point were detonation occurs. Detonation is when the fuel ignites by heat before the spark fires. This gives the dieseling affect.

The reason I don't suspect the thermostat itself, is because you lost operation of the temperature gauge.

The best way to test this is with a coolant system pressure tester. Some auto parts store rent them out and in most cases it's a refundable deposit.

The quick test. Start the car and let it warm up for a minute. Take a clean shop towel and place it over the tail pipe for about 10 seconds, then smell the rag. If it has a sweet bitter smell to it. You've found the problem.

I have worked on one of these 3.1L that wasn't the intake gasket. It was a stud that mounts the throttlebody to the intake that broke and allowed coolant to enter from the water passage that runs through it.

Hope these suggestions help in diagnosing the problem. Good luck.

Something is causing cylinder temperatures to get extremely hot. The diesel sound you hear is fuel knock or detonation. Is there any codes in the PCM? Start there first. Check for vacuum leaks. Try a different fuel, like a higher octane ratting. It is worth having the engine data looked at to determine the problem whether it be a fuel injection problem, timing, or damage internally.

check all your pulleys that the belt goes around as one might be not turning freely or the belt tensioner itself could be bad, get these items checked before you buy a new belt and install it, there is a routing diagram for the belt under the hood of the car or if a 3.1 engine it's on the engine itself on a plate, also look in your owners manual if you have it as it's in there.

You're going to ruin the engine pretty soon if you haven't already. I would start by checking the thermostat and other things related, like hoses, but if you're going to save this car, you'd better get it to a auto technician fast.

you say the exhaust pipe gets cherry red? sounds like there is an restriction in the exhaust, probably the cat. is clogged. the reason it shuts down is the valves are getting too hot because of the exhaust restriction. get the cat. changed.

yes it could be the thermostat . the cooling system could be empty , there could be a belt off the fan is not working or a combination of all of these