Heat

[Ford78david]

I have checked fluid blend door hose temp coming out of heater core but the heat sucks in my 99 expedtion takes forever to get warm but then some days it works great. Have to keep fan on low to get heat if you turn fan up the heat turns cooler.. same for the back of expedition. Any ideas it has the fancy push button temp controls. Thanks

 

[Trainmaster]

With the age of your truck, it's possible that your heater core is clogged. You can try flushing it, or if that doesn't work it would require replacement. It sits behind the dash and the dash must be removed for access. It's perhaps a four hour job if you do your homework.

It's also possible that there's an air bubble in the coolant lines or a head gasket problem that's permitting the coolant level to leak down between driving cycles. Check the coolant level and the condition of the coolant system. Has the anti-freeze been changed regularly? If so, it's less likely that the heater core is clogged.

You can try reverse-flushing the core, and that should give you some relief, though it may be short-lived and you may have to replace it next year.

I've been through this on a 2000. Not a bad job if you watch the videos on You tube, and use the proper tools. Don't cheap out. Use a Motorcraft replacement or you'll be doing the job twice. The cost of having someone do it here in New York is outrageous.

 

[Ford78david]

Thanks both hoses are hot after a drive. Idk some times it blows out hot air great. Been raing all week her in n.c hope to mess with it this week. Tks for your advice

 

[Trainmaster]

The hoses should heat as soon as the temperature gauge starts to rise. If not, check your thermostat. Maybe it's sticking? And of course the water level.

 

[1955moose]

I think Trainmaster nailed it. One last thing, make sure carpet isn't binding down there. From your description it sounds pretty much like flow. Heater core or thermostat. Your SUV is going on 20 years, a lot of coolant and sediment build up if not flushed out. Try the flush, but count on a front core replace.

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[hammerg26]

Not to beat a dead horse and I am still perplexed.
Hoses are hot.
Hot air blowing out, and to about 40 degrees, it heats up. Below that, the heat barely works.
Is that still a flow issue?
Thankfully I live in North GA, so it is not that cold. And I do drive to NC for skiing and heat would be nice there.



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[1955moose]

If both hoses are hot, sounds more like a mechanical thing. Check and see if blender doors are opening/closing proper. Make sure carpet isn't binding something in there. Seen that here. The heater control valve is another check. If it's vacuum operated, make sure diaphragm is good and holding.

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[Trainmaster]

Imagine this.

The heater core consists of a clump of two dozen tubes through which the hot water flows. They are all connected in parallel, so the water flow is split between the 24 tubes. Down 12 and up another 12.

Now imagine that all but four are clogged. You'll still get flow through those four, so both the input hose and the output hose will be hot. Mildly cool air is being blown across the tubes, and those five hot tubes give up some heat to the air. Since the water volume flow through four tubes is less than the designed flow through two dozen tubes, the velocity of the water flow is increased. Thus the water cannot give up all its heat to the airflow, and it exits the heater core at a higher temperature than normal.

Now imagine that the air flow gets colder. Real cold. The four tubes of hot water does dick to warm up the air. That 20 degree air comes out of the vents at maybe 40 degrees.

So you turn the fan to High. The faster the fan, the less time that air hangs around to be warmed and the more air bypasses the few hot tubes. But the water's still rushing through the heater core faster than it should and it's not giving up all its heat, so both hoses remain hot.

Pull out that dashboard. You need a new heater core.


On the genuine possibility that I'm wrong, here's Ford's troubleshooting pinpoint guide for insufficient heat in a 1st Generation Expedition. It's worth reading. The case illustrated was caused by a leaking intake manifold gasket.

https://www.justanswer.com/ford/2w7xg-ok-99-ford-expedition-no-heat-put-new-thermostat-new.html

 

[Yupster Dog]

02 5.4 4x4 here and I am having the same problem. I am going to try the heater core flush. I have purchased 15' of 5/8 ID (inner diameter)that I will cut in half and a female garden hose end. (almost all should fit the 5/8 ID heater hose) and a quick shut-off for end of hose. I have a couple of buckets(and spring clamps if I need them) there are half a dozen videos about how to do this to our trucks. I plan on flushing the core back and fourth about a dozen times each. I believe like said in another thread this is just a temporary fix and I plan to replace the core in the warmer weather of summer if this works. will probably fit this job in my schedule within the next week or two. I will let you know how it worked out.

 

[98eb5.4]

def check/rule out a blend door issue, known to act up & easy redneck fix