Most of my clutch fans seem to "engage" on initial start up and release after a few seconds. I have only had three clutch fans fail. One fan leaked oil and the other two wouldn't engage at the proper temp. All three had more than 150k and a small but noticeable amount of play.
I used a piece of cardboard in front of my radiator to run the temp up above normal and then checked the fan for resistance. On my stock temp gauge the fan kicks in at about 1/2 just above the "R".
I have always replaced my fan clutches with electrics, but thats another story.
regards
rikard

 

The truck has almost 170k on it. I wouldn't be surprised if it's faulty. When you say it releases after a few seconds, does this mean it stops spinning completely or just spins slower?

I'm interested in any trouble shooting techniques if anybody has them to test the fan clutch. I don't really have any experience with mechanical fans, mostly have dealt with e fans only.

Thanks

 

Do I want a thermal or non thermal controlled fan clutch?

 

I think there's your problem. Usually the temperature is stamped on the bottom of the thermostat. Go back and get a 195 and when you take the old one out see what they sold you.

Last time I bought a thermostat in a parts store they tried to sell me a 180, I got into an argument with the guy and they eventually gave me what I wanted but he told me I'd be back when I couldn't figure out why my engine was overheating.

 

assume = *** out of you and me

 

I normally cheack the new thermostat on the stove in a pan of water before I instal it. I use a candy thermometer, and watch for it to open. Sometimes even good brands produce a stinker.
The temp sending unit on my '90 300 is not too hard to change from under the engine. I didn't pull the starter , just streached a little and worked on it when the engine was cold. After changing both the thermostat and the sending unit, mine reads pretty close to straight up on the gauge.
With a new heater core, and the deck screw removed from the blend door, mine now gives 135-140 deg air at the dash vent.
A blend door that is stuck open just a tiny bit can really affect the heater output in cold weather.
If the clutch fan is stuck on, you can tell. It sounds like an airplane, and the truck feels like it is pulling an anchor.
Good Luck Frank

 

Called the parts store and verified the stat is a 195*. I bought a fan clutch and I'm going to try that I think. Hopefully it's a cure. I don't think the clutch has failed completely because it blows a substantially more amount of air when the truck is warm opposed to when I first start it up in the morning. So it's working in that respect, but I'm wondering if it's having trouble disengaging once it has already engaged. A major reason I'm replacing the clutch is there is a bunch of gunk on the front of the clutch. Which leads me to believe the fluid leaked out and gunk accumulated on it.

If this doesn't work, I'll pull the thermostat, test it in some water on the stove.

 

You're wasting your time and your money with the fan clutch.

 

What should I do then? Do you think it's a faulty thermostat?

 

It's either faulty or they put the wrong one in the box when they sold it to you.

 

I have been trying to figure this same issue out with my 302...flushed coolant, replaced thermostat with 180 then 195, replaced fan clutch (twice, first ones was constantly engaged), and replaced heater core. I still get a temp around 110 (in cold weather). The only thing that worked for me was to stick a piece of cardboard behind the grill(with some small holes). I had to give up on this...driving me crazy!...no mechanics seem to know either.

 

Just wanted to thank everybody in this thread that helped me out, especially you andym.

Before replacing the fan clutch, I took the advice to swap out the thermostat for another new one. I took the thermostat housing off, and noticed that the thermostat wasn't seated in the housing properly. It must've slid down during install, leaving a 1/4" gap around the top of the thermostat. So basically what was happening is, coolant was bypassing the thermostat and running through the engine without the thermostat regulating it. So I seated it properly, put it back together and cracked the thermostat housing. Bought a new one of those, put it back together and it works great! It comes up into the operating range within a couple minutes and seems to be resting at about the "O" in normal, just a hair towards the left of straight up and down.

This truck hasn't seen temps that warm since I bought it, I'm glad I finally got this resolved! Now I can return my fan clutch and get my 55 bucks back.

Thanks again

 

glad you got it fixed.

you usually have a huge drag on the engine when the fan clutch goes bad.

seating the thermostat is almost an art on some vehicles.

 

Is a needle reading over the N or O in normal where it should be? I drove it 10 miles to work today and it didn't go above the O. I'm not sure if it should be going to the straight up position or not.

 

that is perfectly normal.

i have an electric fan on mine and with it off, in traffic, in summer, it never reached to R.