Runs hot at idle

[Julie]

Hi. I have an 01 Ram 1500 Sport 5.9. New radiator and heater core about a year ago. 2 weeks ago I was out running errands, drive, shut it off, drive, etc. After starting one of the times I noticed the temp starting to climb and lost heat. Went a little further and the temp dropped and the heat returned. Changed the thermostat that afternoon just in case it was sticking. Since then it hold temp going down the road but when stopped at a light the temp goes up and the heat stops. Corrects itself when I start off again. Not a good situation in the winter. Does anyone know what could possibly be going on?

 

[turkeybird56]

My first thought was thermostat, but U said changed. So next thought is: Constricted hose (Radiator/Heater) and/or maybe Water Pump giving up the Ghost.

Only other afta thought would be: Low Coolant... IMHO

ADDED: U might want take an added look at water pump. Because those "impellers" in there wear down and it takes more RPM pushing water through to cool. Sometimes U may hear a whine. Been a long time since I did a water pump on any Chrysler, think last was Mom's 1972 Satellite Wagon with 318. Been long time, Just thinking out loud.....

 

[Julie]

I didn't think of a constricted hose. I'll check that tomorrow. Thanks.

 

[muddy12]

Still running the stock mechanical fan clutch?
If it’s slipping too much, it may not be moving enough airflow through the radiator when you are stopped.



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[dapepper9]

The fact that you lost heat from the vents points to either a water pump that's dying or a clog in the heater core that's impeding flow. I would unhook the heater hoses from the firewall and blow compressed air backwards through it. Super cheap and easy to do. You can tell which one is the supply by feeling which is hotter when its running. Just don't unhook those while running or hot.

You can also take the serpentine belt off, grab the fan blades and wiggle them up and down slightly. If the pump wiggles around it is in dire need of replacement. If it does not it could still be failing to provide flow but it's otherwise structurally sound.

 

[dudeman2009]

The fact that you lost heat from the vents points to either a water pump that's dying or a clog in the heater core that's impeding flow. I would unhook the heater hoses from the firewall and blow compressed air backwards through it. Super cheap and easy to do. You can tell which one is the supply by feeling which is hotter when its running. Just don't unhook those while running or hot.

You can also take the serpentine belt off, grab the fan blades and wiggle them up and down slightly. If the pump wiggles around it is in dire need of replacement. If it does not it could still be failing to provide flow but it's otherwise structurally sound.

+1

If you lose heat in the vents and the engine temp climbs at idle, then there isn't enough cooling at low rpm. I first think water pump. A blocked heater core should explain the loss of heat in the cab but not the engine temp rising, and a clogged radiator or bad fan clutch would explain the overheating but not the loss of heat.

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