Fearing the worst but first a little background. I bought my Ranger about a month ago on craigslist with 115k miles on it. After purchasing I took it to shop and everything checked out except suspension. After driving I started to notice bubbling in the radiator and could hear it after I turned off the ignition, there was a lot of sludge visible in the overflow. I then proceeded to flush the radiator and refill with new coolant as well as replace the thermostat. The bubbling continued but my temp gauge remained ok. Yesterday while driving to work i noticed the temp gauge hovering near the top. After work I drove home and the temp gauge was still showing hot and I noticed some rattling/pinging when i accelerated. There also appears to be some whitish smoke emitting from the tailpipe. I checked the oil and it was at a good level without appearing milky at all. Does this sound like a blown head gasket? What else could it be? Taking it in to a shop on Monday to have it checked out.

 

Welcome to the forum

Easy and quick test is the Glove Test
Cold engine
Remove radiator cap
Remove overflow hose, and block opening with gum, putty, hose with bolt, ect..................
Coolant/water needs to be down about 1" or more from the top for the test, so drain some coolant if needed

Disable Spark, you don't mention year of Ranger or 2.9l or 3.0l, so unplug coil wire or coil pack, you want a No Start

Put a latex glove over rad cap opening and seal it with rubber band or zap strap
You can use a balloon or even a condom instead of a glove

Crank engine and watch the glove
If it bounces then you have a head gasket problem or cracked head

If it just lays there you do not
100% accurate test

If glove does bounce, remove 1 spark plug at a time and crank engine
When gloves stops bouncing last spark plug removed was from the cylinder with the problem, reinstall it to confirm
Spark plug's end will looked steam cleaned White because coolant is also sucked in on intake stroke and burned with air/fuel mix




The cooling system is there to cool the cylinders as they fire, so each cylinder is surrounded by coolant passages
Blown head gasket or cracked head will leak pressure and air into cooling system.
This "air" thats pushed in displaces coolant in the head which causes the overheating, because air doesn't transfer heat as well as a fluid.
Not uncommon for temp to stay normal at the start of head gasket issue, the little bit of air coming in can be moved thru the cooling system and ends up at the top of the radiator
As more air is pushed in it forms an air dam which blocks coolant flow thru that area of the head, when enough pressure builds up it moves but overheating up has already started

The Glove test will show if compression pressure from a cylinder is being pushed into the cooling system, glove bounces each time that cylinder is on it's compression stroke

Shops use a Block test, because they can charge good money for it, lol, it uses a chemical that reacts with exhaust gases, they sample coolant while engine is running and if Block Test chemical changes colors it means exhaust gases are being pushed into cooling system from a cracked head or blown head gasket, never seen a false negative using this method, but many false positives, so grain of salt
Glove test is a better test but too old school to charge much for, and customers like the idea of a "chemical test" as more modern, even if less accurate


It is less common now a days for blown head gasket to cause coolant to get into the oil system, can happen but not like in the older engines
Cracked head can't cause coolant to get into the oil system

The 2.9l engines did get cracked heads IF overheated FIRST, the heads just didn't crack one day, but if overheated the head metal would expand too much and crack

 

Pretty sure that Ron's glove test will tell you that the head gasket has failed.

Know that head gaskets just don't fail (blow), something has to cause them to fail, so just replacing the head gasket with out finding "that" cause will not fix things.

Most common is blocked rad core due to lack of maintenance of changing the coolant.
When the truck is fully warmed up, or when it's running hot, turn the truck off and reach down into the rad and feel for cold spots _ there shouldn't be any.
A healthy rad will be warm all over.
Internal blockages can also happen with the build up of rust and oxidized coolant.
It will become obvious if or when the heads are removed.

If you plan on keeping the truck and repairing it, have the heads checked for warpage and also consider a valve job since it has over 100k on it.