Hi, ive just got the engine running the other day and im having a temp problem. Head gasket was just changed and theres no antifreeze in the oil. The radiator fan wont even come on, its supposed to at a certain temp right? Could this be thermostat related?

 

What year Ranger?
I assume a 4cyl engine

Radiator and fan are used when there is EXTRA heat in the engine coolant, at that time the 190-195degF thermostat will open a little and let some hot coolant flow to the radiator to get rid of the extra heat.
If radiator coolant gets hot enough then fan will come on

On cold days fan may never come on


If your engine temp gauge is showing over heating then feel the upper rad hose and then a heater hose, they should be the same temp, if upper rad hose is cooler then thermostat may not be opening all the way as it should

 

Sorry, it is a 1993 2.3l
The upper rad hose gets fairly hot i didnt compare it to a heater hose but will. It has been cold as can be lately so the fan might not come on when over heating? When i changed head gaskets i drained coolant out of the engine and rad but after i only refilled the overflow resivor (rookie move right?), resivor hasnt gone down any, should i fill up the rad with coolant and see what happens

 

Thermostat can't work unless there is hot coolant warming it up.
Yes, you will need to refill radiator with 50/50 coolant water

Remove one heater hose at the firewall while refilling radiator, doesn't matter which one, this lets the air out of the engine/head while refilling so coolant can flow into those areas.

Put heater hose back on and leave rad cap off
Start engine
Coolant in radiator should go down a bit after engine is started, top radiator up and put cap on


Drive, or let engine run for 15-20min(or longer), watch for overheating on the gauge, then turn off the engine and let it sit for 1 to 2 hours until it is cold again
Remove rad cap
Coolant should be at the very top of radiator
If not then check Over Flow tank it may be dry now

This is a self Purging cooling system
As engine warms up coolant it expands and rad cap opens and lets some coolant flow out to over flow tank
On cool down the coolant in engine shrinks and this sucks back in the coolant that went out
If there was any air at the top of the radiator when rad cap opened it would flow out FIRST into the over flow tank and bubble up to the top of the tank and be gone
As engine cooled back down coolant would be sucked back in to replace that air
So rad would be topped up every time it cools down



After 20min of running or longer, shut off the engine and try to spin the fan manually, it should be "tight" hard to move, and that is correct
If it spins easily then you will need to remove the 2 bolts holding fan shroud in place
Move shroud back and run your hand over radiator fins in the center of the rad, see if its warmed up, this is what "locks" the fan, heat from center of radiator
Run you hand over all the fins, should be nice even heat, and cold spots are Blocked tubes in that radiator
Rad should be warmer on upper rad hose side and then cooler on lower hose side, that is correct
Hot coolant comes into radiator from upper hose and is then cooled by passing thru the tubes, and then goes back to water pump/engine thru the lower hose

 

Hey that seems to have done the trick!
while i was watching the temp gauge though my rpm tach went out. Could that be a sensor or something?

 

My fan does spin easily btw, should i be looking to replace?

 

Fan clutch works from Radiator heat, so in the winter it may never lock up, radiator has to get hot before that happens

There is a tell tale to watch for if a fan clutch is failing
After engine is fully warmed up watch the temp gauge when you come to a stop, as you sit idling, if temp gauge starts to go up then that could be a sign the fan clutch is failing.
The Fans main purpose is to pull air thru the radiator when STOPPED, when driving the air flow thru radiator is more than any fan could provide, so cooling is not done by the fan when moving

Now a failing water pump can have the same symptom, if coolant wasn't changed every 2 years then the impeller blades can get eaten away by galvanic corrosion, so they can't circulate coolant as well at lower RPMs, idle RPMs, but way more likely for a failing fan clutch to cause rise in temp at idle

 

Since its warmed up this afternoon the fan does kick on. No over heating problems of the kind. I think she may be solid.