i have a 2000 ranger xlt v-6 3 litre rear wheel drive. when i start my truck up in the mornings and have the hood up listening to the engine. all is fine but when i turn the heater on and come back to listen to engine i hear a pop or a bang sound, this happens 2 to 3 times a minute. any thoughts on the cause, this was happening before i put in new radiator and thermostat and is still happening. also air from heater is not very hot. thank you.

 

Can you take a video of the sound? The pneumatic HVAC makes pops and bangs as you change the settings.

 

Unplug the AC Compressor wires to see if noise goes away, AC is ON when heat is on, not just when AC is selected


1995 and up Rangers use an electric motor Blend Door, it fails
The Blend Door in the cab is control by the COLD-HOT ****, this is the only control for heat/temp in the cab
After engine is warmed up turn the **** to COLD and see if air coming out gets COLD and then turn it to HOT and see if air temp goes up
If there is no change then Blend Door motor(actuator) is most likely bad
Google: Ford Ranger Blend door actuator

Loads of videos and hows-tos for that repair

If air temp changes with COLD-HOT **** then blend door is working
Could be heater core is clogged up so not getting very hot
You can flush the heater core using a garden hose, need to flush it in BOTH directions
Heater core is hard to change on 1995 and up Rangers, have to pull out the whole dash board, there are videos on that

Its good to REVERSE the heater hoses at the firewall every 2 years or so, this back flushes the heater core while driving to help keep it cleaner
Heater cores have no "direction of flow" no assigned IN and OUT, so reverse the hoses every 2 years