overheat at highway speed

[gemmersen]

My 4.0L 2002 ford ranger only overheats at highway speeds in 105 deg. F + temps uphill. the problem has been around for a few years because i don't drive it often. i have 33s on it and i've moded the engine slightly. nothing extreme! I've changed the coolant, thermostat, and radiator cap hoping something cheap would fix it. now i'm down to the radiator and pump. i'm looking for suggestions and no it never did it before so the mods aren't it. does the ranger have a clutch fan? the fan spins when the engine is running, elementry to most maybe, but not to me. this problem is anoying because i get 1 crack at it per year usually. it seams to overheat when i need it most, typical!

 

[Big Jim M]

What does "overheat" mean?

If it means steam and coolant spewing out the overflow... Then YES that is overheating!
If it means the temp gauge goes up higher a bit..Then NO that isn't overheating..that is NORMAL.
In 105* and the engine under a load the temp will vary a bit from time to time.
Since the thermostat LAGS in opening the temp is always a little higher than the temp it takes to open the thermostat.
For example we most all use a 195* and yet the temp of our engines is nearer 210* at all times.
As a general rule if the coolant system is KEEPING the coolant inside the engine, the temp should be considered normal.
Big JIm

 

[Big Jim M]

By the way If your forward speed will allow another gear then when you see the temp climbing a little downshift and get more rpm.. This will cause the fan to run faster and also allow the timing to advance.. together they should lower the coolant temperature.
Big JIm