Not guessing here Samnbensdad just my exp. replaced pump, upperhose, thermostat, fan clutch, and scanned radiator with infrared then pressure tested, all good. Overlooked the cap, pressure test revealed that was the culprit, brought it back to AutoZone pressure tested the replacement before I left the store and it was good to go no more problem.

Ive also had thermostats bad out of the box, did you put it in a pot of water on the stove and watch it open?

 

There surely a lot of that that goes on!........

 

no i didnt boil it but.... befor the heads got warped last summer from overheating i was trying to fix a overheating problem and replaced the thermostat... after finding out there was gasses in my coolant i knew the head gaskets had to be done and heads sent to a machine shop... so when they did that they also replaced the thermostat again so that is 2 theremosts in 6 months that have been put in the D.... i can hear my e fan running so i know thats not it ... it overheats when i drive faster than 70 mph... or i have my ac on.... i just did a new clutch fan .. only thing left is water pump or radiator.. all my coolant hoses are not leaking coolant... cap is new i put it on last summer when trying to find out the overheating problems...before the head job got done... still makes me wonder why when i rev the motor a bit coolant tries to push out of the radiator instead of getting pulled down like it should.... that would make sense i think if the radiator is restricted or plugged a bit... to my knowlege the raditor is still the same one that has been in the truck since new... my truck is a 2001

 

Did you burp the system when refilling with antifreeze?

Do yourself a favor and buy plain generic aspirin...take 1, and put the thermostat in boiling water to open it...

pull it out with pliers, and hold the aspirin in the gap of the thermostat opening to hold it open... as it cools, it will clamp on the aspirin...

install it like that, and when you refill the cooling system, all the air comes out the top radiator hose...

start it and top it off... as it runs for the first couple minutes, the aspirin will dissolve and the thermostat will close until it heats up!

Just a trick i learned from a old timer many years ago.....

 

I just went thru Over Heat issues. During winter run cool till over speed or stop in traffic after 40ish mile drive. Did thermostat replacement then went thru the "burp" system cuz it is a 4.7 and possible air issues weigh heavily on over heating I'm reading. Did same thing with rev motor and watch coolant come out top (I assume related to position of thermostat on bottom of block and direction of flow from water pump)..replaced radiator recheck thermostat direction fill coolant properly and its summer with over heat no longer...maybe just lucky thats all it turned out to be.

 

+1 Could be a radiator.


The aspirin trick works, but I've always bought the T-stat with a small bypass in it for that reason. However in a 4.7L motor you want to use the OEM one from the dealer so the aspirin trick should do fine to help alleviate the problem.

Personally I think just checking the T-stat to ensure they work before installation is worth it's weight in gold. And it would be a great time to get a aspirin in there. One thing I don't like about that idea is if you only put one aspirin in it could bend the plate coming down. On some models of T-stats it is only a discus cup that can bend easily.