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hey i have a 2004 4.7L dakota that has been running hot at idle but not over heating, temps fine while highway driving. I've replaced the thermostat which helped for a while, then the clutch fan along with a radiator flush and purged of air.checked the electric fan as well seems to be working fine. also replaced the radiator cap (20 psi) the coolant overflow has coolant but not over filled. i left it with my mechanic to see what he thought said it was fine that it didnt get hotter than 210 degrees.(left idling for 45 mins) i was satisfied with that untill yesterday when i was driving around town (5 miles or so) i hear the serpentine belt squealing and i stop (truck temp also above normal operating temp in my mind gauge just past halfway) and the rad cap was re-leaving quite a bit of coolant (steam and leaks). this is the first time where there was a problem where i felt i needed to stop and check, there had never been a noticeable leak of coolant or any squealing (im guessing from the coolant leaking onto the serp belt). not sure what else could be the problem other than the water pump which i was assured was not the issue. any other tips or advice would be appreciated. thanks.
sry for the novel. :( :confused:
 

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I hate tracking down cooling problems! But here goes; There are several things you can check yourself, but the mechanic should had caught it. Check the hoses, sometimes old hoses will collapse and the collapsed hose will restrict water flow to the radiator. Look at the radiator itself. Sometimes the radiator fins can be plugged up with debris, such as a few pounds of bugs or mud. The fins should not be bent. The radiator could be clogged internally. Has it been pulled and checked? Water pump is the only main component you hadn't messed with...just saying....
Are you using good quality coolant? Water alone isn't as effective and it could cause rust to form in the system, and rusted metal doesn't conduct heat well.
Try another radiator cap and do a pressure test. If it fails the pressure test, you got a leak somewhere. Hopefully you won't have a blown head gasket.

Other places to look. Does your truck have an automatic? If it's an automatic, the tranny is cooled thru a heat exchanger in the radiator. Check the tranny. Make sure the fluid is topped off and clean. If you have any slipping or the fluid is burnt, or if you pull heavy loads with this truck consistently, the tranny is developing extra heat and transferring it into the coolant and could cause overheating. You can improve tranny cooling and reduce overheating by using a quality transmission cooler.

Check the engine oil. Believe it or not, your engine oil can help the cooling system. If the oil is low, the engine can create extra heat, and this can overwhelm the cooling system. Make sure the oil is clean and fresh. Oil breaks down as it ages and doesn't lubricate as well. This creates extra heat that the cooling system has to get rid of.

Modern engines are designed to run hotter, 210 degrees still makes me cringe and 180 to 190 sounds much better. You said the thermostat was changed. What temp range was used? Also was it correctly installed? Sometimes they stick and won't open even when new. You mention that the serpentine belt was slipping. Check the idler, they should spin freely and the spring in it which holds the belt tight should be move freely but still be hard to move by hand. Check the condition of the belt. Once a belt has been slipping for awhile, they develop a glaze and always slip. The only solution is to replace the belt.

Check the engine's tune. If it's a little out of time or running a bit lean, this can cause the engine to run warmer. Normally modern computers are good at controlling timing and fuel richness, but sometimes computers do start to go bad and they can throw the engine slightly out of whack.

Finally never trust a factory temperature gauge to give you an accurate reading. Most aren't calibrated and they can read a bit off even when new. Use a good quality temp gauge or check temps with a good quality temp gun.

Ed
 

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Discussion Starter #4 (Edited)
the thermostat that was used was a 190 degree, the radiator was pulled flushed in oct no worries there, the transmission makes the most sense tho, i had the tranny re built at 175000 and was told to bring it back to have the fluid checked and flushed after 30,000 miles. i am just about at 200,000, so that very well could be it. i dont haul anything too heavy jsut a quad a dirt bike occasionaly, the truck gets most of its work drivivng 150 miles from li to upstate. once the weather breaks i plan on putting a 180 degree thermostat in that i got today. oil levels we good just changed the oil 3 days ago, going to replace the serp belt when i do the therm i appreciate the advice will let you know how it turns out.

if its none of the above i will replace the water pump even tho i was told its was fine. thanks again!
 

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When you check for a collapsing hose. First squeeze the hoses by hand. Some hoses have a spring inside them to prevent collapsing. Pre molded hoses may not have a spring. If you can easily squeeze them, suspect a collapsing hose. To see it for yourself. You'll need a helper. Start and warm up the engine. Have your helper rev the engine to about 2000 rpm and visually inspect the hoses. Sometimes as the engine is running at speed, the hoses will collapse just from the pressure in the hoses. You will not see this if the engine is cool, not running, or idling. Check both top and bottom hoses very carefully.

Ed
 
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