Hey all,I have a 2003 ram 2500 with the 5.7 hemi 170k miles......so to start off,had to replace water pump couple months ago cuz bearing was bad and water coming out of the failsafe hole and while I was at it I replaced the thermostat...made sure jiggle pin was straight up,truck ran good for a week or so,started noticing temp gauge reading over half....normal was always under half,than just last week it overheated way past half almost to red before I noticed and shut it off to let cool down....come to find out the new thermostat wasn't opening...even took it back out and did the boiling water test and still didn't open...so got another new one this time from advanced auto....and BTW these are the oem 203 degree ones....tried it and it's still overheating but just not as bad....even tried a brand new radiator cap,I tried burping the system by driving front of truck on ramps and squeezing the hoses,fan works,it's full of coolant...took it for a drive about 10 miles and got hot again so I took temp gun,the engine head reads 235 and bottom of oil pan reads 220,the upper radiator hose and lower hose temp difference was about 10 degrees difference....lower hose being cooler....so I'm not sure and tried asking around and no one knows,hoping someone on here would know,hate seeing the hemi sick like this,lol

 

Did they give you the wrong water pump?? If it is spinning the wrong way, it won't move coolant... and the engine over heats.

 

Yea I compared it to the old one it was the same

 

My only suggestion is to flush it out ..... I mean add a flushing T to a coolant line and force old dirty water out.
I have done this several times .... I actually prefer to run some cleaning vinegar in the coolant system .... then after a few heat cycles hook a garden hose to the flushing T and flush it clean .... sometimes it takes a few flushes to actually get it clean ...... Not a 5 minute job ..... It is a non evasive job and actually works pretty well.

It would only take one flushing and by watching what comes out, tell you if worth doing it again. ...... Comes out clean forget it .... comes out dirty flush it again.
Like the old saying, you wipe your **** 3 times to find out 2 times was enough .... flush that coolant system til it comes out clean.

Adding a flushing T into the heater hose to connect a garden hose and back flush all the dirty contaminates out of the system ..... A clean radiator, working T-stat A water pump that cycles coolant. .... your issue is dirt and no circulation.

 

You mentioned changing the radiator cap, but have you checked the radiator itself for clogs or leaks? A partially clogged radiator can cause the overheating issues you have mentioned.