bigger radiator.

[lil_Blue_Ford]

So I have used both radiators. You do need to change the lower hose with the Explorer rad. Never had much issue with the fan and clutch, but I did have other issues that caused overheat issues. I took to running a 180* thermostat, and not a cheap one. Had an overheat anyway because I had a leak that I couldn’t find until I discovered the heater core was leaking but somebody sealed the heater core housing with RTV so it wasn’t leaking in the cab nor out the drain hole. I’ve also seen bad water pumps.

I would probably do the thermostat and water pump and see what happens. Plus check for leaks.

That said, PetroleumJunkie has found that some blocks are choked up with casting sand which can contribute to problems too. Apparently quality control wasn’t up to snuff here because Europe doesn’t see some of the overheat issues we do

 

[Shran]

I've used 4.0 radiators on 2.9s, small radiators on 4.0s, big radiators on 4.0s, I think I've had just about every combo under the sun at one point. A few notes:

- There are "big" 4.0 radiators and "little" ones. Big ones would be from a 4.0/automatic with AC, 4.0/manual with or without AC is about half as thick and holds less water.
- Big 4.0 radiators will cool a 2.9 pretty well but I had issues getting good heat in the winter and my gas mileage suffered. I believe it was because the thermostat doesn't open as often, thus the water in the radiator gets colder, and when it circulates back in, it's quite cold
- Little 4.0 radiator does not require hose changes, big 4.0 one does because the lower hose comes out at an angle instead of straight.
- There are different fan shrouds for different radiators that also make a difference here.
- Putting a larger radiator in will not necessarily fix overheating issues... I have a 4.0/auto radiator in every one of my 4.0 trucks, my Explorer still gets hot with the AC on, idling. It cured a lot of other issues I had with low speed offroad travel though. What the truck came with is generally good enough for most people.