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This isn't uncommon on anything with a 4.7, more so on the DR body trucks for some reason. Some of the cores in the radiator will get restricted and not flow, and it effectively reduces the size of the radiator. It will heat up more under a load when this happens because of the increased engine heat being produced. I've seen this in the shop, and have had first hand experience with my own 2004 truck at around 70,000 miles.With the truck hot, use an infrared thermometer or your hand to feel the temperature of the outside of the front of the radiator (away from the fan). The top left of the radiator should be the hottest, the bottom right should be the coolest. There should be a gradual temperature change across the radiator. When cores get restricted there will be spots in the radiator that are cooler than the rest because there is no flow through them.Flushing the radiator seems to have no effect on the problem, since flushing it will not force through the restricted cores. It's easier for liquid to flow through cores that aren't restricted, and it just takes the path of least resistance. The radiator will need to be pulled out and taken to a radiator shop to be rodded out, or replaced.
Forgot to mention heat not working properly. Once engine heats up if you turn heat on only blows hot for few seconds. Does that help?
That makes it sound as if there is air in the cooling system, either from not being bled or from a combustion leak into the cooling system. Did you bleed the air from the system when the work was done? If not then that may be all that needs to be done. If the air was properly bled from the system then a combustion leak test should be done to check the cooling system for presence of exhaust gases.
So a combustion leak would be costantly putting air in system?
Why would'nt it overheat all the time?
Will try bleeding and then the radiator. Thank's for your help. This has been driving me nuts!
I does sound like it's been driving you nuts!
I'd bleed it out and see if the heat then works normal and see if it still overheats. If it still overheats but you don't have a problem with the heat then I'd replace the radiator.
If it's ok for a while and then the same symptoms occur and there is air in the system again or you are having unexplained coolant loss then I'd do a combustion leak test.
Good luck with your truck! If I have been helpful clicking the Accept button will give me credit for helping you this afternoon. Have a great weekend!