befarrer
+1y
There is a drain for the cowl, it drains out the sides into the area between the cab and front fender, and eventually drains between the front fender, just infront of the door. 100% chance this is full of dirt & garbage, which is why they like to rust there. If the drain from the cowl to the inner fender area is plugged, then it will back up into the fan motor, there is only a small lip stopping the water.
As for your heat, what temperature is it around there? Also, have you checked your diverter valve under the dash? These trucks have a valve that shuts off coolant flow to the heater core when not in hot temperature, the valve is on the drivers side, under the dash, near the throttle pedal.
Might just be time for a new core, could be plugged with debris, not allowing airflow, or scale on the inside not allowing heat transfer. I know my heater core cannot keep up once the temperatures dip below -15ºf, it starts blowing cooler air, not sure why. Did that with the previous 2 stock engines, plus the same with my rotary engine. I have had the entire heater box rebuild and cleaned out, but I did not replace my core, just soaked it in vinegar internally for a couple days.