My 01 ram 5.2l has weak heat at idle rev it up and the heat is good . I’ve flushed the heater core 3 times and no gunk came out. The heater hoses both get good and hot. The truck runs at 190 degrees and gets there in the proper amount of time. I’ve parked it on a hill and let it bleed the cooling system and after awhile the heater will start working well only to quit after the next time I drive it or so. I’m at a loss. The coolant level is good . Any ideas?
Weak heater output at idle
- Thread starter ram_man
- Start date
Does your truck have vacuum operated doors that open to let heat into ducts?. If that's the case and it's not working, you won't get the heat. My old dodge would only work on the defroster setting, and it took forever to feel it in the cab. If the core gets hot, something else is keeping the heat from blowing out.,,,
OVERKILL
$100 Site Donor 2021
So, if you rev it and get heat, when you let off, it gets cool again? Sounds like air. Do you have a vacuum bleeder?
I flushed my heater core about this time last year, and got 25f more degrees out of the vents, but it was still lacking its former power.
more recently, I flushed it again, when I changed the heater hoses. I found the heater control valve, which when given a vaccuum closes off flow to the heater core, was about 1/3 occluded with scale on one end. It would be off, in the MAX AC mode, or when the whole HVAC system was OFF.
I don't have AC anymore. I plugged its vaccuum line and deleted it so there is no restriction to flow, and the warmk/cold blend door itself prevents heat from entering vents to cabin. The heat coming from vents now is as good as it used to be, which is impressive.
Anyway look for a valve in the heater hose to the heater core, Iif vaccuum operated, it might be the cause of your issues
more recently, I flushed it again, when I changed the heater hoses. I found the heater control valve, which when given a vaccuum closes off flow to the heater core, was about 1/3 occluded with scale on one end. It would be off, in the MAX AC mode, or when the whole HVAC system was OFF.
I don't have AC anymore. I plugged its vaccuum line and deleted it so there is no restriction to flow, and the warmk/cold blend door itself prevents heat from entering vents to cabin. The heat coming from vents now is as good as it used to be, which is impressive.
Anyway look for a valve in the heater hose to the heater core, Iif vaccuum operated, it might be the cause of your issues
I don’t have one but i agree it acts like an air bubble that just will not come out.
I believe the temperature modes are done electronically.
OVERKILL
$100 Site Donor 2021
I had that problem on my Expedition (which held an obscene amount of coolant due to rear heat) and after a particularly enthusiastic run I was able to get like a gallon more coolant into it, which stopped the problem. Are you hearing any gurgling or anything?
I think by the 2000's those had electric blend motors. I wonder if yours isn't closing all the way? Maybe voltage is lower at idle?
Is it possible that the truck has a blown head gasket? The fact that the hoses are both hot certainly points to air in the system, whether it be underfilled, or combustion gas from a head gasket problem.
The fact you have to keep bleeding the system and it’s fine until it’s shut off again is a screaming clue to the problem.
The fact you have to keep bleeding the system and it’s fine until it’s shut off again is a screaming clue to the problem.
Has no other symptoms. So I don’t think so.
When I first start it I hear a little bit of sloshing in the dash and then again when I first take off in drive. I just don’t know what to do to get the air out.
OVERKILL
$100 Site Donor 2021
Definitely sounds like air then. Vacuum bleeder may be needed, is there a place you can borrow/rent one from?
Many times that is the very first symptom of failure.
Pretty sure Rams used the old vacuum-control setup to the body change in 2002-3.
I will have to look into that I am not sure. We just moved yesterday I have to unpack and get ready for thanksgiving and fix the truck lol
It has an electronic blend door right under the glove box I assume that’s the only
Control for the temp controls?
Are both hoses hot or is one cooler? A flush may help but it wont remove everything.
Embarrassed to say I still have a car with Bowden cables for heat and a/c. No vacuum blend doors. No problems in ten years. If it ain’t broke...
