Ok i recently noticed at idle my truck is getting up to about 235 in traffic. I have AN 03 gmc sierra with a 5.7 ls1 and a front mount turbo. I recently moved from wi to southern illinois and with the warmer weather now it gets hot. I have dual electric fans. just some cheap 14 inch fans from oreillys. I ordered ls1 fans and will have them in a couple days. I am thinking my cheap fans are just not moving enough air? anyone have similar problems?

 

how many miles on the radiator and thermostat?
Dexcool has a bad reputation for "mudding" up and clogging radiators. I have seen it happen several times.

 

t stat about 10k radiator is o e with about 90k on it when i put the new motor in the truck i used the 5.3 heads and none of the cooling passages in the block were nasty

 

Usually a clogged radiator will make one over heat more going down the road than sitting idling, though it wouldnt be a bad idea to have the antifreeze tested for acid content. It could also be a thermostat stuck closed as stated above. When the truck is fully warmed up over 210 touch the upper radiator hose and see if it is HOT. If it is just warm or cool to the touch then your thermostat is not opening. Also is the coolant low?? This could also cause it to over heat.

 

also, check your heater core and radiator fins, i saw someone on tech who had an overheating problem and it turned out that his heater core was full of gunk.

 

thermostat is opening and heater core is not plugged. hopefully more airflow with the ls1 fans will help

 

remove the belt and see if the water pump has drag to it by spinning it with your hand, you'll beable to feel it, i had this isse along time ago, i would heat over 220 at idle in traffic and in the staging lanes, i checked everything i had thought, then i checked the pump by turning the pulley by hand and felt the bearings were dragging, changedd it out and solved the heat issue

maybe a long shot but its worth giving it a try..

 

Is it getting up to 235 with both fans running normal speed (some people call this on 'High')?

 

down in Houston my truck got up to 210 just driving after I did the cam so I just pull my TStat over summer and put it back in the winter.

 

I cleaned my oe radiator when I did my head cam swap , I also put some efans on it, my truck will run hot if I get in stop n go traffic too. I put some cheap fans that don't have a shroud and I also have an oil cooler in front the radiator.Thinking of putting some flexalite fans on it. Tell me if your problem gets better. I can run all day at 100mph and it won't get hot. Just when I Idle.