LB7: Heater doesn't work at idle?

[SparkZ03DMAX]

Been letting the truck warm up in the mornings and usually I leave the heater on so that I jump in it's nice a toasty.

Well...its not hot. It doesn't get hot till I start driving. Any ideas? Before we start screaming HG's and etc. I just replaced Head Gaskets with ARP studs, new Danville water pump, and AcDelco thermostats. Is there air trapped? Anyway to bleed it out?

 

[paint94979]

You just swapped to an oil cooled turbo right? Every since I deleted my stock turbo my truck takes forever to warm up. Shit if it idled for 20 miles it isn't even close to being at operating temperature

 

[SparkZ03DMAX]

Doesn't really have a problem getting to operating temperature, just the freaking heater.

 

[Chevy1925]

So it will get to temp but won't blow heat? Kinda unclear

 

[SparkZ03DMAX]

Bingo. Gets to operating temp, won't blow heat at idle. Not till the rpms are raised does it start blowing hot

 

[Chevy1925]

Sounds more like a blend door issue. If you go back to idle, wil it quit blowing heat?

 

[skidoosleds3]

Clogged heater core?

 

[SparkZ03DMAX]

Sounds more like a blend door issue. If you go back to idle, wil it quit blowing heat?

Yeah

 

[Chevy1925]

And are is getting full heat out of the vents when moving? As in HOT air?

 

[SparkZ03DMAX]

And are is getting full heat out of the vents when moving? As in HOT air?

Yep

 

[SparkZ03DMAX]

So???

 

[dirtydmax]

Partially plugged heater core maybe,just did gaskets so could be full of crap!?Just an idia and there easy to swap.

 

[SparkZ03DMAX]

Could just use the bleed screw on the thermo housing and see if air comes out. Nick just smacked me with a V8, couldve used a V8 moment lol

 

[ryan415]

Sounds like there could be a blockage or air trapped in the cooling system. When the engine is warm check the heater hoses and see if one is noticeably hotter than the other.

 

[Dmax87]

I'd pretty much garuntee a clogged heater core. Drain coolant, remove lines going to heater core at firewall and use high pressure water to flush. Go both ways with the water flow. At idle water flow isn't excessive, more rpm = faster/more volume of water moving from water pump speed, had this happen on a few vehicles. Hope this helps

 

[hondarider552]

I'll have a pulled heater core in a few weeks

 

[Chevy1925]

I would not deem a heater core. They don't go bad like that and I've never seen one do that but I've seen Gm's wonky blend doors cause this issue.

I would try turning the temp knob back a click or two towards cold and see if more heat comes out, I'd also verify the blend door is working as it should and fully rotating.

Make sure your coolant is full as well

 

[AKlowriderZ71]

How did the heater work before the new head gaskets & thermostats?

 

[Wafdof]

I had low coolant and had this exact situation. Cold at idle no matter how long my truck had run and warm at higher RPMs

 

[Awenta]

Heater core delete mod? Adds about 55hp I hear

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