Having problems with my Ranger overheating. I drove to work fine one morning but on the way home it started overheating so I change the thermostat thinking that would fix it then the next day it did same thing. Drove it to work(72 miles) with no trouble overheating but then about 6 MI down the road on the way home it started overheating again. Just wondering what are some things I should look for. Don't want to change head gaskets if I don't need too. Motor is 3.0L

 

Remove both heater hoses at the firewall
Top up coolant in radiator until both hoses have coolant coming out, air is now out of the engine, put hoses back on, you should reverse these hoses every 2 years, to reverse the flow thru the heater core to keep it cleaner so it lasts longer

You always need to let the air out of the engine side of the thermostat when refilling the cooling system, the trapped air causes overheating because it blocks the flow of coolant

After hoses are back on, leave rad cap off radiator and start the engine
Might be an initial "burp" of coolant out of cap opening but that's all, a "burp"
Let engine idle, if there is a steady flow of overflowing coolant then you DO have a blown head gasket or cracked head
If coolant does not overflow then you don't
Put cap back on

Make sure coolant level in the overflow tank is at the COLD level

Drive it for a day, heating it up and cooling it down 2 times, i.e. to work and back home
When its cold again open rad cap, coolant should be at the very TOP of radiator NO AIR at all
That's what the overflow system does, it purges the air and refills with coolant, a little air not alot, lol

If there is air in the top of radiator then there is a problem with overflow hose to overflow tank, or the rad cap, or you have a coolant leak in the engine or radiator
Over a few days of driving there is too much air in the radiator so overheating


Blown head gaskets or cracked heads don't "just happen", they are caused by an initial overheating episode, coolant got low, or a hose broke, and engine overheated without being noticed on the gauge or you "tried to make it home" after it was overheated
So totally preventable
If you buy a used car/truck, previous owner may have blown a head gasket and put "Head gasket seal" in the radiator, this can last a few months but the overheating symptoms will come back, and white exhaust smoke
Coolant in the oil doesn't happen as often now with the better head gasket material but can still be a for sure sign of a blown head gasket

 

I also just noticed what appears to be oil residue in the radiator and coolant reservoir. I've read that it could be atf fluid because the automatic transmission cooler is located in or around the radiator. But in the case of it being atf, that wouldn't cause the truck to overheat would it?

 

No, it wouldn't

But oily looking residue can also be condensed exhaust gases, which would cause overheating

There is a chemical test called "a block test", that can detect exhaust gas residue in coolant, means a blown head gasket or cracked head