Heater blows cold at idle but warm when higher RPM's..??

Would*

 

Hi maybe if the door is electronically actuated there is a drop in voltage at idle some of these components are very picky about how much voltage they need to operate properly check battery and or charging system

 

One easy way to tell if its a Head Gasket Issue. Your radiator has to be full. With your truck running take your cap off of the radiator and watch for bubbles to come up to the top. This is exhaust gasses escaping thru the holes in the head gasket.

 

I had similar issues and just kept moving my temp gauge from hot to cold until it worked. There's a little wire at the top center of your engine bay if you pop the hood. Make sure it gets tight when you switch it to heat, and loosens when back to cool. (Can't remember the name of the "door" it controls) Blend door?!

 

I don't have any wires under the hood. It's call electronic In the 2006 anyways, and I have No bubbles when the caps off and it's running. I'm so lost with this.

 

The bubbles are constant. Your going to have to watch for a few minutes, I should have said that in the previous comment. Did you see my earlier post? When the truck is hot and you shut it off do you hear or see boiling in the overflow bottle? Or do you see white crusty material around the over bottle? Those are another good sign of a head gasket issue.

 

I've let it run for a long time with the cap off, and seem thing and there's no odd sounds or stuff under the overflow cap

 

My 2005 would only boil in the overflow bottle after I shut it off.

 

I'll have to check that it, but I haven't seen anything like that

 

I could here it boiling when I shut the truck off, I didn't even have to raise my hood

 

Sounds like a bad water pump

 

It was a bad Head Gasket.

 

I had a Dodge Dakota years back that had substandard heat. Back flushing the heater core didn't really help. Ended up taking the hoses off the core,plugged the lower end of the core with a rubber plug. Then I poured CLR in the top outlet of the core and plugged it. Let is sit for several hours,then removed plugs and backflushed with water. Bam! Hot heat.

 

It most be something like that I have done everything else

 

I'm going to flush the whole system with a heavy duty cleaner and flush the heater core with CLR unless anyone has advice against this to see if it works

 

Any resolution on this? I don't see one for the OP who started this thread years ago, or for Skier2388 who posted just a few weeks ago. I have the same "sloshing" sound in the dash and no heat at less than about 1500RPM. It's one of those things I've just learned to live with and just turn the fan speed down at stop signs/lights, but it would be great if we could pinpoint the cause and get a good fix for it.

 

Well, now I feel a bit silly about this... I went out to have another look at things. Took the radiator cap off and even though it was cold, a fair amount of air came out under pressure. Now I've got nice hot air again at idle! Must have been something to do with some air trapped in the system, though I don't know how it got there.

 

Read up on these forums about head gasket issues... and I hope I am wrong.

 

Yeah, i gathered from reading this thread that is the path I need to go down now to see if that was the actual root cause. I'm also trying to remember if I did any work in the last few years that might have introduced some air into the system, but my memory is failing me at the moment.

 

The sloshing could be a clogged drain hose for A/C. Accompanied sometimes by water on the passenger floor mat. There should be a drain hose by the passenger side firewall you'll see from under the truck. The lower radiator hose being cooler then the top hose is normal. Unless your in the middle of the desert in summer.