2.3L ('02-'11) 2010 2.3L still overheating after new radiator, flushes, reservoir, thermostat, and water pump

[Wingit]

Hey all, I've been having some overheating issues with my truck (210k mi), even after unloading the parts cannon. Does anyone have any ideas? It only overheats up prolonged inclines (rpm at 3500 for 5+min), and never at idle or freeway speeds. The heater works great after I unclogged it, and the issue persists regardless of AC use. I've not let the temp gauge get to redline since before I replaced any parts, but only because I go slow uphill and never floor it. It would definitely overheat if given full throttle.

The engine was rebuilt less than 10k ago. No exhaust gasses in the coolant, according to my test kit. Head gasket is good. Upper and lower hoses are both firm, and hot/warm respectively. Plugs, wires, and coilpack replaced 500mi ago.

Here's what I know is wrong with the truck, if it helps:

Vacuum leak somewhere, and small exhaust leaks in several places.
Fuel filter is old and possibly never changed. I have the new one and will replace.
The previous owner used the wrong coolant and practically never changed it. The metal coolant pipe on the top left of the block has a lot of corrosion.
Upper and lower hoses are old and had some residue before I cleaned them.
Potential EGR, PCV, and crankcase ventilation problems. Haven't confirmed, but hoses are cracking a bit

Thanks everybody for your help. This truck is like a stray dog to me: formerly abused and I love it to bits, but the lingering problems are very frustrating

 

[2011Supercab]

I'd be overheating also if I was being forced to do 3500rpm pulling a hill for extended amount of time.

What are you doing that requires you to do that?

 

[Wingit]

I'd be overheating also if I was being forced to do 3500rpm pulling a hill for extended amount of time.

What are you doing that requires you to do that?

Towing the wife.

But seriously, not much. Going up a relatively steep hill on the freeway at 50mph with just me in the cab and no weight in the bed. Getting passed by semis. 3500 is probably an exaggeration: 2700-3000 is probably more accurate for sustained rpm

 

[alwaysFlOoReD]

You replaced the rad?

 

[Wingit]

You replaced the rad?

Yes, with a Denso from Rockauto

 

[alwaysFlOoReD]

Fan clutch.
Should be easy to turn when cold.
Should be stiff to turn once warmed up.
Is there a shroud?

 

[pjtoledo]

are you locking out overdrive?
what gear does the tranny shift to?
your Ranger should have a 4.10: 1 rear gear ratio. did the previous owner change it?
what size are your tires?

post a picture of the fan & shroud please.

an old racers trick for short term maximum power use is to turn the cabin fan on high with heat set at the highest setting.
it will get damn hot, but should keep the engine cooler.

I'm a slow typer, so yeah, like alwaysfloored says check the fan clutch.

 

[Wingit]

are you locking out overdrive?
what gear does the tranny shift to?
your Ranger should have a 4.10: 1 rear gear ratio. did the previous owner change it?
what size are your tires?

post a picture of the fan & shroud please.

an old racers trick for short term maximum power use is to turn the cabin fan on high with heat set at the highest setting.
it will get damn hot, but should keep the engine cooler.

I'm a slow typer, so yeah, like alwaysfloored says check the fan clutch.

I'm not engaging the overdrive off switch anymore, as it runs cooler that way. The trans downshifts to 4th, and judging by the sound I think it either shifts to third or disengages overdrive at the steepest parts of the hill.
Gear ratio is 4.10 judging by the door code, but I'm not positive what's actually in the pumpkin since the tag fell off. I'd say 4.10 though, since the truck settles around 2700 at 65-70.

Tires are 235/75R15. I think that's stock

I'll post a pic of fan and shroud. It has resistance when spun cold, but I haven't checked it hot

And yep the heater is always on! That's how I keep the thing from blowing