Mine only got warm when I accelerated or revved up motor...turned out to be waterpump had NO fins left. Engine ran fine. No or missing blades on waterpumpwill result in low coolant flow pressure...so it wont make its way to the heater core like it should. Disconect your heater core inlet hose with the restrictor from the heater core at the firewall and then run the motor...if there's little to no pressure its your water pump. If the pressure is making it spew out like a hose on high then you should be good. If its spews from the inlet hose, reconnect it and then disconnect the outlet hose from the core and see if its spews from the heater core...think about it. If coolant runs fine through inlet hose but then doesnt come out of core...core is clogged. Id try a waterpump before a heater core though....waterpump takes an hour to replace...heater core...10 lol

 

Of course if you're getting heat when the setting is on "panel" but not floor or defrost then its has nothing to do with your core or waterpump or thermostat. It would then be an interior problem...like that control ****...or its switch...or whatever door moves to open up floor, defrost or panel.

 

Thanks for the info. Logic is pointing to the waterpump. Will check heater hose flow this evening. Water pump can't be that expensive and after 200K probably would not be a bad idea to replace.

 

Well I did not read your post close enough. I pulled the inlet hose at the block (ahead of the restrictor) and it seemed to have plenty of volume. Ran out of time and daylight so will pull it at the core tonight if I can figure out how to get to it. Looks like you need to be a midget contorsionist to get in behind the engine. I am still leaning towards the pump as I checked hose temp last nite and the outlet hose will match the temp of the inlet on high revs but is luke warm at idle. Hope so anyways as I don't want to have to do a core.

 

Yeah you're on the right track...keep working on it and you'll get it. If you decide to replace the pump you can follow this article.

http://www.fordf150.net/articles/idx...ater-pump.html

Is there an advanced auto parts by you?

 

I could be stupid, but I don't think i am, isn't the water pumps main job to keep the engine cool? So if the pump is bad, my truck would be overheating? Am I wrong? I'm gonna try a Heater core flush this weekend, any suggestions? I've heard not to use anything but water to flush it.

 

This was my waterpump AND the engine still ran perfect and cool. There was NO blades left on it...so to answer your question...the waterpump can be totally bad and still the engine can run right.

 

I'm looking for detail instructions on how to replace my heater core in my 1999 f150..?

 

http://my.voyager.net/~sscully/F-150...50_Exp_002.doc I used this step by step and I finished it in 5 hours good pics and tips

 

Flush it with soapy water that's how I've alway flushed it lite on the soap though