Cab heater temp drops at eng idle, 2013

[erniet]

I posted this last year and had a few suggestions but none helped. So I will try again this year.
2004 Itasca Meridian 39+ foot, when at engine idle after driving and eng operating temp is normal the cab heater output temp drops signicantly. Take off at the stop sign or speed up after the intersection and heater air temp is back to warm again.
My radiator is full of coolant and overflow tank is at full mark. Engine coolant temp does not drop off at stop sign or low idle. Outside temp is 25-40 deg F. I feel problem is due to 40 ft of non insulated heater hose and low gpm coolant flow at idle.
Besides not driving in these conditions does anyone have any suggestions/ideas/fixes? Thanks

[wrvond]

Have you checked to see if the heater core is full? If you have an air pocket, especially a large one, you'll see this kind of behavior.
The easiest thing to do is park on a (fairly) steep slope with the heater radiator higher than the heater. Carefully remove the radiator cap, then run the engine up to temp. Run the heater on maximum. This should purge the core and the lines. If you have rubber lines, you might try squeezing the intake line (before it gets too hot to handle) to help the process along.

[87Rockwood]

A lot of car engines do that now, it is normal. It is because of smog control. The hot water is by-passing the heater and is being saved for the engine to keep it hot and low emissions. Has to do with the heater hot water pick off point. At low water speeds (idle) it does not go in the heater pipe. My 98 Neon is the same way.

[Tony Lee]

Amount of water pressure and volume pumped by a centifigal pump is proportional to the square - or is it cube - of the pump rpm so at idle it is barely moving any water anywhere. Doesn't matter because the engine isn't producing any heat either. Add the restriction of 80' of hose and you won't get anything up at the front.

If you really need to fix the problem then you might get a fair bit of improvement by fitting a 12V water circulation pump in the delivery line.

[1ciderdog]

Originally Posted by erniet

I posted this last year and had a few suggestions but none helped. So I will try again this year.
2004 Itasca Meridian 39+ foot, when at engine idle after driving and eng operating temp is normal the cab heater output temp drops signicantly. Take off at the stop sign or speed up after the intersection and heater air temp is back to warm again.
My radiator is full of coolant and overflow tank is at full mark. Engine coolant temp does not drop off at stop sign or low idle. Outside temp is 25-40 deg F. I feel problem is due to 40 ft of non insulated heater hose and low gpm coolant flow at idle.
Besides not driving in these conditions does anyone have any suggestions/ideas/fixes? Thanks

My 2004 Journey does similar. Could be the nature of the beast.
Bob

[erniet]

The 12 volt pump might be an idea to try! I can not get to much of it but I think I will insulate the pressure line, I don't know if it will do any good, but it can not hurt. For no more replies that I get, I don't think many people drive in cold weather!

[terry735001]

i would back flush the heater core make sure there is no trash in the in coming side of the core

you can get trash after a new install parts a pieces from making the setup

all so make sure there is no very hard turns in the line

all so make sure there is no 0/4 battery lines / wiring on top of any of the 80 foot of line you have it can crush the rubber line in the frame

i good place to look is in the small space next to the fuel tank and frame this is a small space with alot of workings running through it or at rear ax

if it working at higher RMP then it could be like i said high RMP is all so higher PSI and some thing setting on the line would cut of flow


all so have to add if your RV make hot water for the shower then you all so have to make sure in that part of the system to the things i talked about

hope this helps

PS some smaller things is
wrong water pump pully size for low rpm speed ..on motor
impeller on water pump in motor going bad .. seen this befor
poorly made setup/made system .. but if this was it you would see more ppl asking about it

[Petro]

Our Horizon works good. One thought I have is perhaps your heater control valve is not opening fully. If you can get at the valve you could bypass it to see if that helps. Just a thought.

Don