'03 Ram 1500 4.7 Overheating

Hey guys, I'm hoping someone can lead me in the right direction with this issue here. My truck is a '03 Ram 1500 4.7, and since I've had it (About 2-3 Years), it's run very well until today. It started earlier this afternoon, I was hauling my 19ft Prowler camper and all of a sudden I heard a chime and my check gauges light was on. I quickly observed the gauges and found my temperature gauge sitting in the red. So as quickly as I could I pulled over and shut the truck off.

At this point I thought maybe I got a glitch in gauges, so I cycled the key to the on position but the gauge still stayed in the red. After this I opened up the hood and started checking a few things, oil, coolant, and for any leaks but all seemed fine. So I decided to just wait it out, about 30-40 minutes until the temp dropped. Once it was just under half on the temp gauge, I started the truck and observed everything in the engine compartment and everything seemed to working correctly. So I got in my truck and proceeded to drive a little slower to see if that would help. But just after 5 minutes of driving at 70 KPH, the gauge started to climb past half and continued to go up. I managed this time to pull off on a side road and figure out my options.

After contemplating a bit I decide to try unhooking my trailer and seeing if it would overheat without the added load. But before I could attempt this a family member seem me and decided to offer assistance by pulling my trailer home for me. Anyhow, he let me go first and everything seemed fine for the first 5 minutes again. But then the temp started to climb again but stopped 3/4 of the way on the gauge and stayed there for bit, but it fluctuated up and down a little driving at just 80 KPH. But when I got to climbing a couple hills on the next highway the temp started to climb a little higher until I hit flat road again then it dropped back down to 3/4 on the gauge and stayed there.

Regardless, I managed to get the truck home, but I'm hoping I didn't cause any engine damage running it 3/4 of the way up on the gauge. But now, I'm at a loss at what the issue could be. It's the first time it's ever done this. So it kind of has me a little worried. So does anyone have any idea of what the issue could be..? I had the T-stat changed last January and the cooling system flushed and filled. And I apologize in advance for the long post. Just wanted to be a thorough as possible. Any help is greatly appreciated.

My truck used to overheat at idle but cool at speed... Replaced fan clutch and solved it.

Something else I found with my truck is that I didn't have a coolant overflow tank, so when the truck heated up it would just expel coolant out the radiator cap hose and onto the ground. Made a cool one out of 6" clear acrylic pipe and hose fittings.

Check upper and lower rad hoses for temperature difference, should be slightly different temperatures. If it's an extreme difference maybe a blocked radiator?

Does the truck cool very much at idle? Could also be a water pump issue which is also a relatively cheap/easy replacement.


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Just read the bit about hills fluctuating temps, aside from the assumed rpm increase that might be a sign of air in the system


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Hey guys, sorry it took me so to get back with an update. I've been running around trying to get this thing solved. Anyhow, I changed the t-stat with the recommendation of another mechanic, (Not Mine). And that didn't change a thing. Truck still hovers about 3/4 of the way on the gauge and goes into the red if I even try and haul my camper. Can't figure that one out. Either way, it's running hotter then usual, which has me concerned. That and I can't use my camper because I can't haul it because of my overheating issue.

Now I have a new t-stat installed as mentioned, and there's no coolant leaks that I can see. I haven't tried replacing is the radiator cap on the expansion tank. From what I can tell it looks like it has a couple cracks in the big seal of the cap. Not entirely all the way through, but at least half way which may be effecting my pressure inside the system. So since it's a relatively inexpensive piece I may as well try replacing it to see if that helps.

But what's strange is the issue seems to happen more on the highway. Worse when pulling something and adding that load on the engine. My brother keeps telling me it might be a head gasket issue or a cracked block. I honestly don't think it's that, so I'm leaning more towards a clogged radiator of a failing water pump. Just don't know which one I should try replacing first. Anyhow, I appreciate any insight anyone could offer me. And apologize again for not responding sooner.

changing the cap will likely make a different (not sure if all the difference) since our 4.7's overflow caps are under pressure.

Also, make sure the system is properly blead. I had to do mine a couple times. There is a bleeder valve on the engine side of the upper radiator hose, only crack it when the system is COLD. Keep doing this a few times (it helps parking nose up on a steep hill). Between those two things, my engine became stable.

JPT said:

changing the cap will likely make a different (not sure if all the difference) since our 4.7's overflow caps are under pressure.

Also, make sure the system is properly blead. I had to do mine a couple times. There is a bleeder valve on the engine side of the upper radiator hose, only crack it when the system is COLD. Keep doing this a few times (it helps parking nose up on a steep hill). Between those two things, my engine became stable.

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Definitely burp it after replacing the t-stat. Like he said. Park it with the front end elevated on a steep hill for a long time (overnight), then open the cap and rock the truck a little bit like you're testing the shocks. If its not dead cold, and it needs burping, it will depressurize and shoot out at you. NAPA sells a block tester kit with a color changing fluid to test for hydrocarbons in the coolant. That would hopefully rule out a head gasket issue, and it isn't as expensive or time consuming as replacing the head gasket if it doesn't need it. It also doesn't require special expensive equipment.

Thanks for all the help guys. But the problem is finally solved. I had an appointment to go see my mechanic today and he decided to try doing a rad flush. So when he went to flush it the water exiting the rad wasn't coming out much. He continued to try flushing it out for the next 10-15 minutes but nothing. It still came out slow and there was no gunk coming out at all which he thought was strange. So he suspected something inside the rad might of broke and got lodged restricting coolant flow.

So i got a new rad installed and she's now cool as cucumber. No more overheating. And the temp stays just below half on the gauge where it's suppose to be. Anyway, just thought I'd give everyone that update. I appreciate everyone's help in trying to help me figure it out.

Cheers..!!