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Not sure if my heater was ever strong or not, just bought the truck this fall. Got a 200° thermostat and the engine runs 200-205° Cab heater works, but barely. Not enough heat to keep me dogs warm now that temps are dropping. Of course I live in Portland Oregon so temps here are still only 40's
I would also add to the list if you check the other things and are still not getting heat.
Flow through the heater core. It could be gunked up and need a back flush.
That said I would do all the other things first.
Also if a coolant system flush was done and the heater core was not back flushed
at that time you might need to do that now.
I did a hose water flush when I swapped engines, didn't back flush anything like I should've but also didn't chemical flush either. So, yeah it might need a flush.
Okay I tested the blend door actuator and it's working, also the blend door axle and it appears and sounds like it's working. Vacuum line by oil cap intact.
Did you try un hooking BOTH heater hoses and running water through just the heater core? Do a reverse flush on it with a garden hose and see what comes out.
I haven't felt them as 87crew dually suggests. I'll do that tomorrow.
I didn't flush the core seperately either. Just left unhooked while doing the engine swap. The heater core presumably has 335k miles on it now, and 332k were heavily abused by others so I wouldn't be surprised if it needs a flush or a replace.
I was hoping to delay a full flush as I didn't want to loose my fancy coolant that is almost new, but do you think the chemical flushing agents are important for anheater core flush also? I suppose I could re use most of my coolant if I can capture it well enough. And I suppose I could just do a core flush without losing much coolant.
