Another heater question
 

I know, you do not want to read another heater question, but here goes.

This is a 94 2.3l ranger, no valve, heater blend door is cable operated.
My heater used to heat, now it won't
Flushed the cooling system.
Replaced the water pump, thermostat.
disconnected the heater hose from the temp sending unit and used a
garden hose and filled up the cooling system till it was coming
out the top of the radiator.
I put everything back together drove the truck after the truck
heated up, I had heat for
about 3 min. before it turned cold.
Any help would be appreciated.

Did you back flush the heater core?

Or at least check the flow thru the core with garden hose?

On my '94, Heater core cost under $30, 2 hose clamps, 4 screws and it is out, takes about 30min to change, if you had to do it again it would take under 15min. lol.
My original lasted almost 20 years so no complaints.


Do this run engine up to temp and feel both heater hoses, both should be hot, now turn on heat in truck and set fan to High.
Wait a few minutes and feel both hoses again, if one is getting much colder then there is not enough coolant/water flowing thru core to keep it warm, fan is blowing all the heat away from what little flow there is, tubes in core are restricted or some are blocked.