Question about 2002 GMC Sierra

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2002 duramax will heat up underload but not at idle any ideas why

Why won't my duramax heat up at an idle

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  • jscullen Jan 06, 2009

    just don't understand why it only heats up when it is working hard. It is really cold out and just doesn't get warm. You would think it would throw warm air all the time not just when you work it. Thank you


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No diesel I have ever owned will heat up to operating temp while idling. I have had semi's and dump truck and a Dodge with a Cummings turbo diesel. If you don't idle a diesel up to around 1200 rpm while sitting the combustion chamber temperature will drop because the diesel does not ignite fully at low rpm. You may also notice after an extended period of idling 1/2 hour or more that when you pull away the exhaust will be whitish blue because of the unburnt diesel fuel sitting on top of the rings. Also extended low idle will wash down the cylinder walls with unburnt diesel and remove the oil from lubricating the cylinders and rings. Hope this helps you understand why your diesel won't heat up while idling. Mike

Posted on Jan 06, 2009

  • michael sinclair
    michael sinclair Jan 06, 2009

    talk to the dealer or auto parts/performance shop and see if they have a winter front available for your truck. diesels are happiest when they are working. without a winter front on my trucks they will only heat up when i am working them. Mike


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