No heat at idle
 

Working on my wife's 2003 Excursion with a 6.0L Power Stroke Diesel
No heat, replaced the heater core,water pump, thermostat we have heat driving down the road but not at idle,Checked the blend door and it opens and closes ,the door is not cracked and the motor appears to be operating normally
The heater core is hot above an idle is so hot you can't touch it, but at a idle its cold. any ideas out there ,Thanks

Alot of no heat at idle problems stem from failed head gaskets. You could check the in-line heater valve near the alternator to make sure its opening and flowing coolant.

I'm having the same problem with an '04 extended cab. Truck runs like a top with 240,000 miles, just no heat at idle. Mine doesn't have a heater control valve.

How long of an idle are we talking about here?

There seem to be multiple threads recently with this issue and I think a further investigation is warranted.

sounds like the head gaskets
 

If you are driving down the road and the temp gauge is normal, the minute I let off the pedal the hot air goes to cold, I've heard back form Ford and they say the same thing about the head gasket leaking, so all get them on order Monday and all let you know the out come,Thanks

If you are driving down the road and the temp gauge is normal, the minute I let off the pedal the hot air goes to cold, I've heard back form Ford and they say the same thing about the head gasket leaking, so all get them on order Monday and all let you know the out come,Thanks

The factory temp gauge is nothing but a cold/normal/hot gauge. Basically an idiot light with a needle. Are you blowing coolant out of the degas bottle?

I had this problem with my 6.0 and it was as simple as a low coolant level.

Don't be ordering head gaskets just on that word. There are several issues which can cause what your explaining. May also be a warn water pump impellar. Do a coolant test to see if there is CO in the coolant and also do a pressure check of the cooling system. Blocktest Kits for CO are available online. See the following video and you don't need the EDAS installed.
HEAD GASKET TEST for 6.0 POWERSTROKE - YouTube

I noticed that too lately



This is one of the first things I would check



I just dont know about a bad headgasket causeing this can someone tell me why a Bad Headgasket would cause this. Does the extra pressure in the coolant system Disrupt the Coolant Flow to the Heater or something.

Usually when you have a Bad HGs you have Temp spikes and overheat conditions along with coolant puke.

so with that said shouldnt the heater Blow Extra Hot???

To me if you have heat out of the Heater while your going down the road and then have NO HEAT at Idel then you have a Coolant Flow Issue

be it a Bad Water Pump or say a Bad Cavitated Front Cover or maybe even a Low Coolant leval and maybe even a Bad Coolant Bottle CAP or even a Heater control valve thats stuck not opening all the way like it should I can see it being alot of other things besides a Head Gaskets Bad

Im just trying to wrap my head around the Fact a Bad HGs would cause no heat issues in the Cabin of the truck. so If anyone has a therory on this I would Love to hear it.

I just had the same issue before I tore mine down, little or no heat at idle. I am wondering if you can hear any venting out of the degas bottle. I had a low pitched whistle on and off throttle from the degas bottle from the increased pressure that released through the cap. Just installed head gaskets and studs and the venting went away and now my heat will chap your face.. lol
I can only guess that bad head gaskets are related to the heat issue due to the coolant flow and pressure. dunno.
I'm sure someone with alot more experience than me could explain it.

Same issue here... but my "problem" started after I did a lot of work including head gaskets, studs and EGR delete.

I'm curious... how many people with this problem have a functional EGR cooler still in place? I sort of figured that without the additional heat from the exhaust being dumped into the EGR cooler, the coolant might lose it's heat pretty fast at idle since these engine's don't really get hot at idle speeds. The only flaw in this theory is the abrupt changes in temperature while driving... if I go from driving under power to just coasting, I can feel the change in temperature from the cab heater.

So... to get some useful data... tell us about:

1. EGR or NO EGR?
2. Cold, Temperate, or Warm climate? (I call cold -20 celsius, temperate would be slightly above freezing, warm would be anything above 15 celsius)

I lived with no heat at idle for a couple of years before I finally done the HG's, tried all the usual stuff but I was just in denial, t-stat, EGR delete, water pump, heater core, oil cooler. I never even really had any puking but upper rad hose would get fairly hard pretty quick so I always thought it was putting pressure in the cooling system.

I deleted the EGR when I did the studs and gaskets. Heat works great without it. Heats up quickly and stays hot.