I have a 2002 Dodge Ram SLT 4.7, bought new. I started having overheating problems about 2 years ago. This year, I have replace the water pump, had the radiator pulled and checked, replaced the idler pulley, belt, temp sensor, thermostat twice. I do not lose any coolant, and it only heats up when it is over 90 degrees out travelling at 65mph. when I slow down it will cool down. I was told by a dodge mechanic that I needed to replace the thermostat with a mopar thermostat instead of a NAPA thermostat. Any suggestions? I have a ton of spare parts!!!!

 

Welcome to DF

I will move your post to the 3rd gen ram section.

 

My 2000 dakota with the 4.7 gets pretty hot when climbing long steep grades.
Hwy 17 here in cali is a 1,500 foot climb in a few miles and during summer there are overheated vehicles on the sides of the hwy everyday.
it is a test of the cooling system to be sure.

When you say overheating what do you mean?
Have you any way to measure the temperature besides the dash gage?
Using 50/50 coolant and water?

For reference my 4.7 will just touch 200 degrees on the gage before the fan clutch locks up.

It has never gone beyond 200 in my case even in stop and go traffic at the top of the mountain after a long pull.

You should hear the fan clutch make that fan roar when it gets hot like that.
The silicone clutch becomes viscous at higher temperatures and there is a delay between when engine heat is conducted to it through the shaft and when it locks up.

Maybe the fan clutch is getting weak?

 

Believe it or not, the most common mistake when installing a thermostat it making sure that the weep hole in the thermostat ring is facing upward (towards top of motor), allowing all air out of the system. And yes, folks install them wrong all the time. Air can stay circulated in your cooling system and in turn cause cooling issues.

 

Have you been fighting this issue or 2yrs or just decided to do something about it now?...yikes.
The radiators are WELL KNOWN for causing overheating. Sure coolant can flow through them, but that doesn't mean the internals between the fins aren't clogged/gunked up.
If you've flushed the system, had a new t-stat installed, had the clutch fan checked, then I would go ahead and replace your radiator, and not with the cheapest one you can find either!
Every 4.7L owner who has had overheating issue's has solved their problem with either a clutch fan replacement or with 99% of them replacing their radiator and giving the system a good flush.

 

I just replaced thremostat to a low temp thermo when my truck started to overheat, that didnt help the overheating just getting it colder, took it to a radiator shop when the radiator started to leak they tried to fix it but ended up with a new radiator(due to clog once the clog was blown out it showed several other small holes seems to be a dodge thing)then next i tired a wter pump there was nothing wrong with mine but it was worth a shot, 5 months later im still trying to figure out what the heck is going on!

Btw it overheats one time per start and usuallly wont do it again until a few min after the next start.