03 5.7 Hemi overheats under load

[Doyle King]

Truck runs hot when pulling my boat up hills and in hilly terrain. Gauge will go from 12 o’clock to just over half way to the red line. New crate motor at 241,000. Now at 400,000. Never had a problem with new motor until a couple years ago. Temp ran normal until 330,000. I have replaced the heater core, water pump, thermostat, fan clutch and coolant bottle and radiator. It still runs hot under load.

 

[huntergreen]

Are you in need of a coolant flush and new antifreeze ? Is it at the right concentration?

 

[wgreggking]

Is it normal at any time?
Transmission temp high? Is it cooled in the radiator?

 

[Daw14]

Try a new sender .

 

[Doyle King]

Are you in need of a coolant flush and new antifreeze ? Is it at the right concentration?

 

[Doyle King]

50/50 and coolant is fresh.

 

[Doyle King]

Is it normal at any time?
Transmission temp high? Is it cooled in the radiator?

Always runs normal until I put a heavy load and hills. Trans temp has never been a problem. Both my mechanic with 30 years experience and I are baffled.

 

[Phirebeard]

Is your radiator partially blocked by debris? Possibly a fan binding so it's not spinning as fast as it needs?

 

[Doyle King]

New radiator, water pump, heater core, fan clutch, bottle and thermostat, fresh coolant-proper mix. I've done everything I can think of. Always runs normal even in 100+ temps, unless it's loaded and in hilly terrain.

 

[GTyankee]

The only thing that i can think of with all those fairly new parts, is that your temperature gauge is malfunctioning

 

[huntergreen]

Or one of the new parts is defective.

 

[wgreggking]

Never boils over?, maybe borrow a temp gun check rad., trans line , or get separate transmission cooler, cheap enough takes some of the heat from the radiator, change the t-stat maybe partially not fully open, you could move to Illinois flat as a pancake!

 

[huntergreen]

How big is this boat ? Trailer brakes ? If so, may there is an issue with them or wheels on the trailer.

 

[Smokeybear01]

Short of moving to Illinois, is there any chance of a blockage in the engine block slowing down coolant flow? Or a thermostat not opening fully when it should? Not sure how you could check the block, but I'm leaning toward that thermostat

 

[jws123]

I have gotten bad tstats out of the box so many times... take it out throw it in boiling water see if it opens 100%

 

[Ronald E Shelton]

May sound ridiculous, but after chasing a very similar scenario for months, found the A/C Compressor was dragging which created overheating in hilling country?
Worth a look . . . . at a minimum!

 

[Mardye]

I had a similar problem when I had my 03 and it turned out to be the thermostat. The non Mopar stat had a smaller opening than stock so it was restricting the coolant flow.

 

[Dusty]

I had a similar problem when I had my 03 and it turned out to be the thermostat. The non Mopar stat had a smaller opening than stock so it was restricting the coolant flow.

One of my sons had the very same experience! When replacing a part, especially with aftermarket, I always do a side-by-side comparison. Been bit too many times.

Regards,
Dusty
2019 Ram 1500 Billet Silver Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 3 June 2018. Now at 69778 miles

 

[turkeybird56]

50/50 and coolant is fresh.

WHEN U changed/flushed, did U get the system burped and all the air out of the system? My only thought and/or water pump failing/clogged-malfunction T-Stat. Especially being in Texas.

 

[Dodge 1500 4X4]

WHEN U changed/flushed, did U get the system burped and all the air out of the system? My only thought and/or water pump failing/clogged-malfunction T-Stat. Especially being in Texas

If there is any air in the cooling system it will create the problem you are having, is it a new radiator? get a temp ir gun and measure the radiator return hose (your upper hose) and the (bottom supply hose) you should get a big difference temp if the radiator is cooling the antifreeze.