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I have a 97 ford f150xl 4x4, it doesn't have heat, it's been cold lately & i need heat so my kids can ride I the truck
I flushed the radiator, heater core, all new antifreeze, blender door works, never over heats
I need to get this fixed asap
If i turn the heat on it runs hot for about 5 secs then goes cool, i can turn it back off for a min or 2 then back on & same thing again This is the temp it runs at
If i turn the heat on it runs hot for about 5 secs then goes cool, i can turn it back off for a min or 2 then back on & same thing again
As long as the blend door is going all the way over to the heat side, your heater core just isn't passing enough coolant to stay hot. Even though you've flushed it, that doesn't mean all of the passages are passing coolant.
FWIW, the blend doors are problematic and do break. So even though it looks like the shaft is moving on the outside, the actual door might not be moving on the inside. If you go to https://heatertreater.net/products/ford/f150 they have a quick fix so that you don't have to pull out the entire dash.
Just because you flushed the core and your flush runs through it doesn't mean that coolant is flowing through it when the engine is running and up to temp.
You need to get under the hood and see if the inlet and outlet hoses are BOTH hot or not. Without hot coolant continually circulating through the core at volume, you will never have proper heat.
In other words, you need to determine which side of the firewall you need to be addressing.
I kno the blend door works bc i cut a hole to look into the blend door area & it's moving properly
I'll check the heater core hoses when i get home tonight, last i checked before i flushed it the outlet hose was warm, like you could hold it with your hand
Brand new tstat, I'm sure the water pumps working since not over heating, I'm going to try removing the heater core & flushing it again, first time I was kind of doing it in a rush considering it was 15 degrees out at 7-8pm lol
Just because the engine shows no sign of overheating does not mean the pump is working effectively, especially in cold weather. I've seen plenty of pumps with eroded impellers that caused your exact symptom. I've also seen OTHER faults cause it, so don't jump to any conclusions yet.
If you got satisfactory flow through the heater core during your flush, it is not restricted. Doesn't mean it's not good or bad, but it wouldn't cause the symptom of a lukewarm outlet hose.
Your symptom is of inadequate flow of HOT coolant THROUGH the core. That means you need to think about the following questions:
1. Is the coolant at the supply source actually HOT? (Thermostat not stuck open, leaking, backwards, etc. Just because it's new does not mean it is good.)
2. Is the HOT coolant being pushed THROUGH the core? (The pump pushes the coolant, no restrictions in heater core loop, etc.)
Figuring out the answer to those questions will allow you do diagnose the problem.
If you get heat for a few seconds, then cold, you're not getting enough flow through the heater core. Replace it!
Not necessarily on the replacement. The exact same symptom can occur if, for example, the pump impeller is eroded or if a coolant line has collapsed internally.
Replacing the core is a VERY big job, you do not want to do it and then find that you overlooked something much easier to repair.
Not necessarily on the replacement. The exact same symptom can occur if, for example, the pump impeller is eroded or if a coolant line has collapsed internally.
Replacing the core is a VERY big job, you do not want to do it and then find that you overlooked something much easier to repair.
The OP said he was going to remove the heater core and try to flush it (again) - my suggestion is if you're going to the trouble of removing it, simply replace it at that time.
I agree that on something this old, it makes no sense to not replace the heater core if you've gone through the trouble of removing it. However, I would check everything else prior to changing a heater core because of how big a pain it is. As for water pumps, the impellers don't tend to wear out. The bearings do. It's a simple and cheap replacement and on a truck this old, it certainly can't hurt.
03-16-2017, 09:16 AM
