1999 F150 5.4L. With the engine off and turning the ac/heat **** I can hear the blend door open and close. Also when doing that I can feel a difference in air flow at the panel outlet. When the engine is hot, upper radiator hose very hot, I don't get hot air coming out the panel outlet, just air. Could the thermostat be stuck? Also the coolant overflow container never gets hot. The lower radiator hose never gets hot like the upper one does.
Lots of stuff going on here and any ideas will help. Thanks in advance.

 

sounds like either the heater core, or one of the pipes going to the heater core are plugged up.

check up under the wiper cowl on the passenger side, you should see two rubber lines running into the fire wall. If one is colder then the other with the engine hot, you need to try and flush the lines out, and maybe are in need of a new heater core.

generally the radiator is doing its job if the lower hose is cooler then the upper. The lower should be warm/hot, but not scolding hot like the upper. If the lower is ice cold then you may have a problem with your radiator also

 

Have you checked your coolant level? Low level will also cause your symptoms.

Steve

 

I am having a problem with heat in my 98 f-150.

I am not getting hot air in the cab.

The engine gets warm, but does not go above the normal tempature.
The top hose gets warm but doesnt hold pressure.
It seems as if both heater hoses are warm so it must be circulating.

I am pretty illiterate when it comes to mechanical work, but can't afford a garage. Can anyone help me with this.


Thanks in Advance

 

See message # 3 first.

 

nevermind

 

I was noticing a sound like a vacum leak once the truck was turned off. It quick soon after I noticed it. Both heater core hoses are both hot. The top hose is hotter than the bottom. The over flow tank has plenty of fluid in it. It really has me puzzled.

 

The Hot/Cold air flow is controlled by a damper that is vacuum actuated. Since you seem to have hot water going into the dash this might be the problem. Check to see if the damper door that controls hot/cold air going into the cab is functioning. Ford seems to have trouble with the damper actuator failing or the linkage between the damper actuator and the damper falling off - I know of a few that this has happened to. You could also have a vacuum leak between the AC controls and the damper actuator.

You may be able to see this from underneath the dash. The shop manual calls this thing a temperature blend door actuator. If you pull the radio you should be able to see it.

Good luck!

John

 

The blend door is working. I flushed the radiator with ford flush. I disconnected the hose that goes to the heater core in the engine compartment and hooked a hose to it. I get good water flow into the core in both directions. Is there something that controls water flow through the heater core? I know it is not pluged up but I don't get water flow through it when everything is hooked up and running. Also I noticed that the hose that goes to the heater core has something in it that might be a water flow restricter or something. Does anyone have a guess why no water gets to the core? Thanks

 

Found the problem. Since there was no water flow from the heater core hose I thought of the water pump. When I took it off there were no vanes left at all. This is the first time I experienced a bad water pump that was not leaking from the seep hole. Anyway, 50$ later and a new water pump I now get plenty of heat. Life is good again.