Is there an easy way to tell if you (I) have a bad fan clutch?

My truck runs cool on the highway, but the temp gauge starts to max out once I get behind slow traffic or when at a traffic light. (I'm in Austin, TX at the moment and the temp is in the upper 90's.)

And just so you know, a couple of weeks ago, I flushed my cooling system, changed thermostat and all that good stuff.

But I am having a problem with my radiator drain plug (****). Apparently, I bought a piece of crap drain plug because it seems to unscrew itself and starts to leak. So I imagine this could somehow cause my engine to overheat too, but I am betting it's the fan clutch. Any thoughts?

 

One way to check that I know of is replace it. My luck with fan clutches they usually lock up and roar like crazy and rob power, but it will never over heat.

 

Most will roar during the first start in the morning for a few seconds if they are good.

 

When I bought my current '83 F-150 with a thirsty 351W V8, it had no fan shroud in place. I replaced the shroud and drove it awhile and noticed that at low forward speeds the temp gauge would climb.

Replaced the fan clutch, and this all stopped. Never had another problem.

I dont see how the larger engine trucks run without a shroud. The fan is so far back from the radiator that it kind of defeats the purpose of pulling air thru the radiator.

 

My 83 460 has a shroud... or are you talking caterpillar class?

 

No. Talking about our trucks where someone has removed the shroud and not put it back.

Of all that I had to do to MY truck when I got it, this shroud cured the most problems.

 

That's one major problem with body lifts. The radiator moves up, but the engine stays in the same place, so you have to cut the bottom of the shroud out.

 

Some 300-I6s and 302-V8s did not come with a fan shroud, it came with a fan guard.
Most of these did not have a/c. A/C and/or Supercooling has a fan shroud.


To check the fan clutch I would need to know which one you have. You either have a centrifugal fan clutch, or a thermostatic fan clutch.

With the centrifugal fan clutch, (does not have a spring on the front), you can grab a hold of it, (with the engine off and not running), wiggle it up and down for bearing play, (should be no up and down play) and turn it to see if there is any resistance. With the centrifugal fan clutch there should be slight resistance when you turn it. This is because the fan is activated by centrifugal force and only begins to slip when it reaches a predetermined RPM.

With the thermostatic fan clutch, (with the spring on the front) check it for bearing play and resistance (with the engine off), but this time there should be very little resistance with the engine cool. If the engine is already warm. Take a piece of cardboard and block the radiator with it for a moment. Start the engine and let the engine temp rise for a few moments and the fan clutch should engage and start to roar loudly. Keep watch of the temp gauge, if by half way on the gauge if the fan clutch doesn't kick in, it's bad. This is because the thermostatic fan clutch works by engine heat and temp.