My 03 Chevrolet s10 extreme 4.3L is sending White smoke through my air vents and from under my dash, also is steaming up the windshield when I accelerate my tuck above 60 but when I’m accelerating to 30 or 35 around town it doesn’t smoke it just streams up the windshield the smoke has a burnt rubber smell to it also I don’t have my air on when this happens, it’s currently running on five cylinders due to a misfire in cylinder three but I wouldn’t think that would make smoke come out of the vents and underneath the dash and just today it wanted to bog down and not really accelerate any advice on what it could be would help thanks!
Your truck has a leak in the heater core. Engine coolant is circulated through the core to provide heat to the cab. Most vehicle heaters circulate coolant through the heater core even when the heater is turned off.
It's unlikley that the core can be repaired, 'tho a radiator shop would be the place to ask. I am not familiar with the heater and dash design in this vehicle, but it's also likely that the dash will have to be removed in order to access, remove, and replace the heater core.
There are undoubtedly stop-leak products available that promise to take care of the problem. Were it my vehicle, I wouldn't put that sort of product in the motor's cooling system.