well , owned this 98' 2.5 , rear wheel XLT going on 2-3 years. I flushed the whole cooling/heating system when I bought it . shortly after I bought it I replaced heater control valve. since then great heat. but; I hear at random times when nothing is turned on , a clap or tap coming from the dash /vent area . not loud but I can hear it. Now , I've lost the hot air. watched some vids and other research . decided , prematurely to cut out bottom of duct to gain access to blend door . mistake and totally unnecessary in this case ; but still helpful cause now I know the actuator and blend door are both working fine. today I flushed and reverse flushed the heater core ; also the radiator and the rest of the system - and still no heat coming out of the vents in the cab . all the hoses get hot. one thing that bothers me is the petcock for the radiator only dribbles water out . at the moment I have antifreeze in the overflow mounted on the fender well but none in the radiator since the petcock only dribbles water out. soon I'll open it and let the radiator drain out and put some coolant /antifreeze in the radiator . only other reason I can think of is the heater control valve . any input is extremely welcome . hope I can get heat for the winter . thanks everyone .

 

If both heater hoses going into the firewall are hot, my guess is your heater core is mostly plugged/blocked by sediment.

 

+1.

 

thanks guys.

I saw a vid where the guy put CLR into his system . anybody know if it's safe to do that?

 

Only put CLR or Vinegar, mix with warm/hot water, into the heater core, let it sit 20min then blow it out, repeat until you have better flow, reverse directions every other time

If you run CLR or Vinegar in the whole cooling system you will create a lot of debris that you won't be able to drain out very well
So just use it on the heater core or radiator separately

 

OK , I think this answers all my questions. thanks a million Ron .