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Heat blowing cold car getting hot fast 98 malibu 3.1 v6

ok so the other day an idler pulley went and snapped my belt and ruined the other idler pulley got the belt and 2 new pulleys put them on and everything was fine… now this morning i dropped my gf off at work and within the first mile the temp was just about at max and heat wasnt working (cold air) ac worked fine though…also it seemed to cool down when i drove a bit its really weird i would think thermostat or air or heater core but doesnt seem like any to me with alll these charachteristics any help would be appreciated thanks

Let me put this in my own words,you continued to drive when the indicated engine temp “was just about at max” This was not a good move on your part. Can you justify doing this?

Double check the routing of the serpentine belt. You may have the water pump running backwards. I see this from time to time.

How many miles on the car? Maintenance done (coolant changed) lately? I would doubt that the heater core would fail at this age car, but you didn’t state the mileage, so maybe. But why would that cause the engine to overheat? Doubt that. The thermostat is more likely and a cheap bit of insurance if you haven’t changed it lately. Change the radiator cap as well. For an engine to go to MAX temp within one mile means that virtually no coolant was circulating at all, IMO. Lack of coolant would also answer why you got no heat from the heater, as there’s no fluid to circulate through the heater core. You also suggest “air” and I suppose you mean air in the cooling system. You could eliminate this possibility by bleeding the air out after you check the coolant level. Did you check the coolant level? I would check the coolant level, change the T-stat and radiator cap and re-check the belts and pulleys. Rocketman

It sounds like a textbook case of over-heating resulting in a blown head gasket.

yea it started cooling down when i drove it was when i was sitting there smoking a cig waiting for a drink and it was pouring rain out and i cant walk to good

makes sense but i figured it would squeel like a pig if that happened ill def double check on that again

It sounds to me like the coolant is low, but you probably checked that, didn’t you?