I have a 2004 silverado 5.3 z71 with 235,000 miles. I replaced the water pump and fan clutch about 1 year ago. I also replaced the thermostat about 1.5 years ago. My problem now that its getting hot down here in Florida is when I sit at an idle I notice on my rearview mirror the temp outside read 90 degrees and after idling for less than 5 minutes the temperature read 112 degrees outside. I immediately looked down at my engine temp gauge and noticed it was creeping up over the 210 degrees mark. I started driving again and then the temperature on my reaerview mirror went back to normal outside temp readings and my engine gauge went down to normal as well. I also noticed my AC was blowing a little warmer at an idle and then changed to cold when I started driving again. What can I do to diagnose my problem without buying all new parts again. Has anybody converted fan clutch to electric fans and if so has that helped? Thanks in advance for any help.

 

It sounds to me that you kinda know what the problem is and I have to agree, the fan is not pulling enough air through OR you may have some debris blocking good air flow... Summit racing has electric fans as does JC Witney, its all a matter of how much time adn money you are willing to spend on the endeavor...

Start by making sure the radiators are clean and unobstructed it may also be time to consider a new radiator if there is build up in the old one...

 

Had similiar problem on my '99 Silverado 5.3 4x4. problem with plugged radiator after 200K miles. Went to RadiatorExpress.com and purchased a new radiator for a better price then local and have had no problems with heating since then. Did the same as you and replaced waterpump, fan clutch and thermostat along with hoses and belts. Good Luck