Cooling fan doesnt come on after initial startup

[rkneeshaw]

When I first start the truck I can hear the cooling fan spin up (sounds like an airplane taking off), but after that initial spin up, it quiets down and I never hear it again. I'm guessing this is because it only comes on when needed (e.g. coolant temperature reaches a certain level).

Well I was in 4x4 crawling up a sand trail in 1st or 2nd gear tops and the truck's temp needle went past the L in NORMAL, almost into the red as I reached the top of the hill and I never heard the fan fire up. I shut off the truck for while and let it cool down.

The truck doesn't get too hot as long as I'm driving on roads, usually 55mph or so.

I'm nervous about overheating next time I go on the trails. Shouldn't I have been able to hear the fan spin up faster once the temperature got that high?

 

[Explorin94]

Sounds like your clutch is bad. That is the piece that the fan blades bolt too. You will need some clutch fan wrenches to take it off or an air hammer. If you are not sure which way to turn the big nut to get it off simply start the truck up and see which way the fan turns and turn it the opposite way taking it off.

 

[--weezl--]

it does sound like a worn out clutch, what is your mileage?

easy way to test it is spin the fan with your hand, it shouldn't spin too far, maybe 1/4 to 1/2 a turn after you let go... the way i do it though, is drive it so it's hot, and shut it off and try that, if it is really loose, you need to replace the clutch... alternately, you can always put an electric fan on... but the conversion is going to cost a few dollars, and unless you get a kit, there are a few draw backs... (namely it won't come on automatically)

alternate to a kit would be go rip some fans off a vehicle in the junk yard, taurus e-fans are a popular item on the newer rangers, and something that i am thinking about putting on eventually...

 

[rkneeshaw]

She's got 187k on the odometer

I did the test though: with the engine off, spin the fan with my hand it it moves maybe 1/4 turn or so after I let go. Its not totally loose at all, it has some friction to it.

Could a bad temp sensor cause this? Maybe the PCM thinks the temp is always at or below normal and therefore doesnt turn on the fan?

 

[Big Jim M]

The fan has fluid in it. When not turning the liquid seeps into the ON place in the fan. Then when the engine is started the turning of the fan allows the liquid flow into the idle location in the clutch. The front of the clutch has a heat sensitive spring on it. As this spring heats up it grows in length and opens the "idle area" which allows the liquid to turn the fan again. If the spring is worn out and no longer performs as designed, the fan will come on at first startup but won't come back on when the spring heats up..
In short I'd be looking for another fan clutch.
Big JIm

 

[rkneeshaw]

Big Jim, that is excellent information. I'm going to look into changing out the fan clutch, thats got to be the problem. Thank you!

 

[BRUTUS_T_HOG]

just to add.. a sure way to test the fan clutch is to run the engine at fast idle till its hot and the thermostat is open.

then shut off the engine and watch the fan blades.. they should not make more than 5 turns once the engine stops

 

[sholzy]

Sounds like your clutch is bad. That is the piece that the fan blades bolt too. You will need some clutch fan wrenches to take it off or an air hammer. If you are not sure which way to turn the big nut to get it off simply start the truck up and see which way the fan turns and turn it the opposite way taking it off.

If it's the 94 4.0 then it should turn counter-clockwise to loosen. My 93 fan shroud has a direction arrow molded in on top to show which way to turn the nut. I never noticed it until recently. I didn't have a clutch wrench so i just put a wrench on the nut and gave it a sharp tap with with a 5lb hammer and it loosened right up. The old man taught me that trick. I guess he still knows more than me. :

 

[BRUTUS_T_HOG]

If it's the 94 4.0 then it should turn counter-clockwise to loosen. My 93 fan shroud has a direction arrow molded in on top to show which way to turn the nut. I never noticed it until recently. I didn't have a clutch wrench so i just put a wrench on the nut and gave it a sharp tap with with a 5lb hammer and it loosened right up. The old man taught me that trick. I guess he still knows more than me. :

just a tip for you guys. fan clutches will unscrew in the same direction that the fan rotates

 

[bcost882]

If it's the 94 4.0 then it should turn counter-clockwise to loosen. My 93 fan shroud has a direction arrow molded in on top to show which way to turn the nut. I never noticed it until recently. I didn't have a clutch wrench so i just put a wrench on the nut and gave it a sharp tap with with a 5lb hammer and it loosened right up. The old man taught me that trick. I guess he still knows more than me. :

the old timers usually do and with the current generation they always will. it is a clutch problem. so deff swap it out, and which ever way it turns is loosening btw, they really did make left and right hand threads

 

[sholzy]

the old timers usually do and with the current generation they always will. it is a clutch problem. so deff swap it out, and which ever way it turns is loosening btw, they really did make left and right hand threads

The 75 year old might be a little slower these days, but he is still one of the sharper tools in the shed.

If I remember correctly the '90 to '97 4.0 was counter-clockwise and everything else was clockwise. But I've been wrong before...

 

[tonyjklh]

that is definitely a bad fan clutch. i had the same thing happen. was climbing some hills and fan quit working. but unfortunately the gage was way wrong!! only went half way up. next thing i know it was boiling. also you dont need the fan clutch tools. just get a chain clamp and put it on the pully. than get you wrench on it.

 

[mge_1]

that is definitely a bad fan clutch. i had the same thing happen. was climbing some hills and fan quit working. but unfortunately the gage was way wrong!! only went half way up. next thing i know it was boiling. also you dont need the fan clutch tools. just get a chain clamp and put it on the pully. than get you wrench on it.

I noticed the coolant was boiling on my 95 B4000 also the other day. So its the fan clutch huh? Wow ok glad I read this thread. Thanks.

 

[--weezl--]

I noticed the coolant was boiling on my 95 B4000 also the other day. So its the fan clutch huh? Wow ok glad I read this thread. Thanks.

just because you have one of the same symptoms as this person, doesn't mean you have the same problem, do a little more looking into it, before you go replacing parts, just to save yourself a few dollars if that ISN'T the problem... overheating/coolant boiling can be caused by many things, motor running lean, plugged (inner)/dirty (outside) radiator, non functioning thermostat... ect

 

[tonyjklh]

I noticed the coolant was boiling on my 95 B4000 also the other day. So its the fan clutch huh? Wow ok glad I read this thread. Thanks.

i agree with "weezl". i was just pointing my experiance to the original post, since it was the same symptoms as with my truck. but in your case i would start with the thermostat, or if you do a lot of deep mudding clean your radiator, a radiator filled with mud doesn't help.