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

Has anyone fix this problem I put a new thermostat in and I had the front and elevated on ramps i ran it up to normal temperature couple times, even let it sit for 24 hours with the radiator cap off and the coolent didn't go down so I don't think theres any air in it, exactly how stubborn is the air and should I go for the water pump the coolent is in really good shape so I'm not thinking it's a block heater core or partially blocked heater core but I'm kind of at a loss I have none of the signs that would indicate it's a head gasket

 

My dealer said there no problem is there supposed to be a big difference in temp from idle to 2000 RPM??

 

Please help I am at a loss, I have replaced the thermostat (with an OEM one) and flushed out the heater core, I have 2 concerns my lower radiator hose seems to never gets warm(even on long rides) and When the temperature gauge on the dash says it's up to running temperature and I have a spillproof funnel I don't see that there's any flow of the coolant like the water pump is pushing the water around is that all that's normal and my other thought is its normal for this truck like a design flaw for the 2006 model. I was thinking of replacing the water pump with an OEM one but my concern is that it won't help and it's an expensive part

 

What did your coolant look like? Was it rusty?

 

No looked like it was brand-new. And the same came out of the heater core perfectly clean but I noticed today on my way in but my lower radiator hose was significantly cooler in my upper one I'm not sure if this is normal

 

I had a similar problem with another truck. I back flushed the heater core with a water hose. It blew out some built up gunk in the line. Maybe try that? Or something of the sort.

 

I did that yesterday and it didn't help much at all and nothing bad came out

 

Well the coolant coming out of the block is going to be hotter than the coolant going back in "If everything is working properly". I've seen the blades on a pump almost rusted all the way off a Chevy, over heating because there was no flow. If you can rev it and it gets hotter then you may have a flow issue. Bad pump or a clog somewhere.

 

Ok thank you I'm thinking I'll replace the pump.

 

You have an air pocket.

 

I'm pretty sure I got all the air out I used all the tricks I found online

 

So I had 2 dealerships tell me there's nothing wrong. But I am still not getting very good heat at an idle, i have replaced and flushed every thing I can think of. So my question is, is it ok to put those head gasket repair in a bottle thing in the coolant system or will it clog every thing up?

 

Skier2388: I had exactly the same problem, it was started with idle overhead during Arizona summer time. I changed thermostat, replaced radiator, water pump, flushed few times, no help, 2 weeks ago I flushed the heater core, still not fix the problem, As I can hear boiling under hood after long drive, I start to think my car is head gasket issue. maybe I'll replace that this week to see if that fix the problem.

 

@bcf When you shut your truck off do you hear or see your coolant boiling in your over flow bottle? That's what mine did. Or do you see white crusty residue around your over flow bottle? Again that's what mine did. I had head gasket issues.

 

Mine is not doing anything like that, the only thing I'm getting is very low heat at idle and a very thin White residue under the oil cap that's very thin and could be expected this time of year in New England so I'm still at a loss as to what to do

 

Did you replace the water pump?

 

Yes and the thermostat and flushed the heater core but I'm thinking maybe I didn't flush it out well enough

 

Have you pressure tested the radiator?

 

Sounds like the Blend door actuator is bad

 

What it change with idle I can't find anything online that suggest that