I have a 2003 F250 Super Duty 5.4L V8 with no heat. It wasn't missing, running funny or blowing white smoke out of the tailpipe and there were no coolant leaks nor did it overheat. Thermostat has been replaced twice, heater core flushed twice, water pump replaced, fan clutch replaced and blend door works...Cabin airflow gets colder when turned from hot to cold. This thing is sitting in my driveway and I am about to push it over a cliff. Did I mention it only has 56,000 miles on it? Coolant was drained to replace water pump and flush heater core (again, water ran through in both directions with no stoppage). 3 gallons of undilluted antifreeze was put into the overflow bottle to be topped off with water...the coolant went in and stopped. Engine was started to force coolant from bottle...coolant backed up into the bottle and out the top. Heater core inlet hose is hot and outlet hose not very warm if at all. Upper radiator hose is soft. Didn't check lower radiator hose as I was a bit peeved and slammed the hood closed and called it a night. I have been throwing money at this thing that I do not have and am at my wits end with it. Any help is GREATLY appreciated!

 

Same kind of problem. 04' f-450. Just did head gaskets, Egr bypass, new oil cooler, and replaced the thermostat. Seems that although the top radiator hose is fairly hot, the lower hose is somewhat cool to the touch also the heater core hoses do not seem very hot. I checked the blend door and actuator and both are working fine. The truck does not over heat or blow coolant out of the degasser bottle cap. The bottom line is that the heater core is not getting hot enough to blow warm air into the vents. Might I need to replace the water pump now. If there is anyone that might know, I could really use some knowledge. Thanks for reading.

 

First verify the T-stats OK, Cheap T stats can be bad out of the box. Stant makes a Heavy duty T stat. Sounds like you've made sure the system is full. Is the rad cap holding pressure. The fact that the upper hose is soft means blockage or one of the rad caps are not holding system pressure.

Does your truck have a heater core shut off valve? Thats a valve usually vacuum operated running off the intake or rear of the block. Said valve prevents hot coolant from entering the heater core when using the A/C or when the temp is in the cold position. If its not opening or partially opening that could cause these symptoms.

If that checks out then it sounds like you have sludge built up somewhere. The system needs a good flush. Remove the heater core hoses and flush them out separately, again. The engine water pump wont move the crud out of the core like garden hose pressure will. Even with low miles you could have crud somewhere.

Radiator could still be plugged. That's a classic sign of a plugged radiator when the bottoms cold and tops warm. Radiator might clean out OK or need to be "rodded" out by a rad shop or replaced?

Have the system pressure tested to see if it will hold 15 psi for a few hours. If not somethings leaking.

To really flush your system well, you will need to take all the hoses off and get into the lower rad connection, the engine block, the heater core...etc.... all separately with a garden hose. Flush until it all runs clear. Sounds like you may have already done this?

Once your confident the cruds out and the water is circulating then button it all back up with the old hoses. Then flush it again with a high quality cooling system flush. While your running the flush check to see if you have heat and that pressure is built up etc... If you still do not have heat then drop the flush and inspect the pump impeller.

Be sure you have all the flush...flushed out of the system before adding new coolant.

Drain all the raw water and flush mixture out per the flush instructions. Raw water isnt good for the system. Then install all the new parts hoses T Stat etc... and fill with 50/50 premixed or straight antifreeze cut 50/50 using distilled water. Dont mix with tap water. Too many minerals in it.

 

Well it was the water pump. The impeller (plastic) had a crack through it and the pulley wasn't turning it on the inside. Thanks so much doldsmorland for your input and help with this. So glad there are people out there like you with so much good information willing to give good advise.

 

Plastic has no business inside an engine! Glad you followed up and found the problem. Was the pump factory or a replacement? Did the new pump have plastic too?

 

Yes new Ford factory replacement is also plastic. Horrible design!

 

Ya I agree!