Overheating issues

[mwh0428]

I have a 1993 explorer 4.0 v6 5sp 4x4 it has overheating issues that seem like they are getting worse. I got it over the summer it sat for about two years before I got it. I changed the thermostat when I first got it and it ran great never got hot after that. That was 3 months ago. Now lately it's been running hot and has just gotten worse. I have changed the radiator, thermostat again, and water pump it's still overheating. When it gets hot the heat really isn't the warmest. Any suggestions are highly appreciated.

 

[RonD]

First thing is to check for cracked head or bad head gasket, once that is off the table then you can move on to other causes.

Easy and free test is the Glove Test
Cold engine
Remove rad cap
Remove overflow hose from rad, block it's port, vacuum cap, gum, putty, hose with bolt, ect....

Put a latex glove over rad cap opening and seal it in place with a rubber band or zip tie
You can also use a balloon or even a condom in place of the glove

You want a no start so pull off the 4 wire connector on the coil pack

Crank engine and watch the glove, if there is a cylinder leak the glove will bounce up and down
If glove bounces, remove 1 spark plug at a time and crank engine
When glove stops bouncing last spark plug removed was from cylinder with crack or blown head gasket

If glove just lays there, no bouncing, then cylinders are good

Your description reads like a cylinder leak, "air" is pumped into cooling system from this leak, it collects at the top of the engine, air rises, the heater hoses are also at the top of the engine, as air builds up it displaces coolant and engine starts to overheat, heater gets air in the hoses so you lose heat in cab as engine gets hotter.

If overflow tank is getting full, it is also a sign of cylinder leak

4.0l OHV engines have a weak casting in the heads that will cause them to crack when over heated, this could have happened before you got the Ranger, the crack will slowly get larger and larger.
Head gasket issue is much the same gets worse over time.

Coolant in the oil is no longer 100% with cylinder leak, newer gasket materials hold that off, it happens but "no coolant in the oil" is not a sign head gasket is OK

 

[mwh0428]

First thing is to check for cracked head or bad head gasket, once that is off the table then you can move on to other causes.

Easy and free test is the Glove Test
Cold engine
Remove rad cap
Remove overflow hose from rad, block it's port, vacuum cap, gum, putty, hose with bolt, ect....

Put a latex glove over rad cap opening and seal it in place with a rubber band or zip tie
You can also use a balloon or even a condom in place of the glove

You want a no start so pull off the 4 wire connector on the coil pack

Crank engine and watch the glove, if there is a cylinder leak the glove will bounce up and down
If glove bounces, remove 1 spark plug at a time and crank engine
When glove stops bouncing last spark plug removed was from cylinder with crack or blown head gasket

If glove just lays there, no bouncing, then cylinders are good

Your description reads like a cylinder leak, "air" is pumped into cooling system from this leak, it collects at the top of the engine, air rises, the heater hoses are also at the top of the engine, as air builds up it displaces coolant and engine starts to overheat, heater gets air in the hoses so you lose heat in cab as engine gets hotter.

If overflow tank is getting full, it is also a sign of cylinder leak

4.0l OHV engines have a weak casting in the heads that will cause them to crack when over heated, this could have happened before you got the Ranger, the crack will slowly get larger and larger.
Head gasket issue is much the same gets worse over time.

Coolant in the oil is no longer 100% with cylinder leak, newer gasket materials hold that off, it happens but "no coolant in the oil" is not a sign head gasket is OK

Did the glove trick and got no movement what so ever. I called a couple buddies and one told me to take the thermostat out and see what happens. It never went above 190 degrees. I went to the auto parts store and bought a 180 degree thermostat instead of a 195 degree. Made a trip to work and back home (about 25miles one way) and seems ok now. Every now and then it climbs up to around 210 but cools down right away. But my heat is not real warm and it's 40 degrees outside.

 

[RonD]

Go back to 195deg thermostat, better for engine and better for you, best MPG with 190-195deg t-stats
A working thermostat has nothing to do with overheating, using a 180deg or a 195deg t-stat on an engine will not change anything if there is a cooling system problem.
That 15deg difference is nothing if cooling system has a break down, overheating happens fast on a breakdown.
But long term the 195deg t-stat will make for cleaner oil, good for engine life, and better MPG, gasolines conversion to energy is more efficient with coolant temps above 190deg.
Both these facts are from SAE(Society of Automotive Engineers), yes mostly known as the "oil guys" lol


Pull out the heater core, 4 screws and 2 hose clamps, very easy to do
Look under glove box, there are 4 screws, I think 8mm heads, 3 are at 3 lower corners facing up, one is at last corner but higher up, you can see it if you lower glove box door all the way.
Put a towel down as some coolant will spill out as you angle the core to get it out

Flip core upside down(outside the cab, lol), all coolant should drain out, core should be very light then, shake it, if you still hear coolant inside or it still feels heavy, core is clogged up, replace it

Heater core is the cooling system by-pass, as it gets clogged up coolant temp will go high and then back to normal, for no real reason.

While heater core is out check Blend Door operation
It is cable operated in 1993, the COLD-HOT lever on the panel
In cold position the Blend Door Covers the heater core so no air from the fan can pass thru it, by-passes heater core
In hot position ALL air from the fan passes thru heater core
In between positions Blends the cold and warm air to set cab temp
Cable runs to the top of the air box, with glove box down all the way you can see the cable and how it changes Blend Door position
Put your hand up in the air box while heater core is out and operate Blend Door to make sure it is moving and opening and closing all the way.


If any engine starts to get higher coolant temp at lower speeds or idling then most likely cause is Fan Clutch, could be water pump but usually Fan Clutch.
At faster speeds the fan is not used, vehicle speed causes enough air flow thru radiator to cool the coolant as it flows thru radiator.
At lower speeds and idling fan needs to provide that air flow.
Fan shroud and fan clutch are important at lower speeds and iding

 

[mwh0428]

Have to say you hit the nail on the head with this one pulled heater core out and could not get all the coolant out. I went to the auto parts store and bought a new one and it runs awesome. I will change the thermostat out hopefully tonight. But thank you for the help.

 

[RonD]

Good work

Thanks for posting the fix