i am 100% sure it is the fan clutch. i did another test today at school.

when you spin the fan by hand, there is resistance when the engine is cool. when the engine is at operating temperature and you spin the fan, there is very little resistance. this tells me the fan clutch is starting to fail.

i'm seriously considering going with an electric setup because i do soo much stop and go driving and i plan on keep this bucket of bolts around for a while. i also plan on adding larger tires to my itty bitty 2wd pickup soooo an electric fan will vastly improve performance, mileage and cooling. i'm going to explore some junkyards over the weekend. i gotta act quick, there is too much aluminum in that engine for me to keep fartin around.

 

the reason it doesnt overheat while driving, is because enough wind is getting through the radiator through the grill. when its idling, the fan obviously isn't giving it enough air. the fan clutch is almost definitely the cluprit.
but hey, just because you replaced your thermostat recently doesnt mean its good. new stuff breaks too, especially 2 dollar thermostats from kragen
but yeah dude its probably the fan clutch. it wouldnt hurt to flush out your radiator and put some fresh coolant in there. and if its leaking, get a new one, dont pour that stop leak ☺☺☺☺ in there, or stuff like this is going to happen


i don't know what the big deal is with electric fans...why are they so much better? and doesnt it require some modification? i don't really know how much, but i wouldnt want to do it. your fan clutch went out on a ~10 year old truck....its not like that makes it an unreliable cooling system. just replace it with a quality part and everything will be good and simple. thats what i'd do

 

I don't think it's the fan clutch at all. I think it's a radiator if there is resistance on the fan clutch or it is on for the first 30 seconds or so on cold start up it means it works but the reason it is not coming on when it gets hot is because the fan clutch relys in hot air coming through the radiatir to make it come on, there is a heat sensative spring on front of it and when the air is too hot the spring turns and locks on the fan. When the radiator has a blockage coolant cant flow in the rows of the radiator so therefore the air coming onto that spring on the fan clutch is cool air and the fan clutch doesn't think it needs to come on even though the vehicle is overheating. I have seen this a million times. Radiator.

 

i'm convinced it's the fan clutch. if there is no resistance when turning the fan by hand at operating temperature, the fan free-wheels and the engine will overheat due to lack of air being pulled through the radiator.

i'm looking at some electric fans on ebay and i'm giving it some serious consideration. an electric fan will reduce the load on the engine, therefore increasing performance and mileage. it will pull more air through the radiator, thus improving cooling capabilities versus the stock fan and clutch assembly. this will be a worthy investment because i am planning to run 235 75 15 bf a/ts on my itty bitty 2wd pickup with a stage 1 suspension kit from downey off-road.

i will keep posting as i go along. thanks everyone for your input and advice and keep it coming!

 

I think you would be better off with a new radiator. The clutch is supposed to free wheel until it heats up (above operating temp). Heat is what engauges it. You can get a HD radiator from radiatorbarn.com for pretty cheap. On my 22RE with 35's and the OEM 2-core radiator the needle only moved about normal once. 90* towing 4K lbs up a 6 mile pass at 4K feet, then it moved 1/8" and stopped...

 

Fan Clutch!

 

i finished installing my brand new proform 15" diameter electric fan i bought on ebay for cheap. my overheating problems have disappeared and i gained a little extra power.

i also installed a new thermostat while i was at it. so far so good. i really doubt the radiator is plugged judging by it's physical condition. the top of it is hot, the bottom is cool. if anything, the bar's leak contaminated the old coolant before i flushed it all out.

when i dismantled the stock fan and clutch assembly, there was a build of dirt and grease all over the bi-metal spring that engages the clutch. it's clear to me that the fan clutch was the culprit behind my overheating troubles.

if anyone is interested, i'm thinking about posting some pictures. this fan was worth every penny and every second spent installing it. it's has a built-in adjustable thermostat and relay, all you have to do is connect to a high amp and low amp 12v power source and splice into the wire that powers the magnetic clutch above the a/c compressor. i'm also probably going to add a manual over-ride switch for extra control. there is a thermostatic sensing bulb made out of mercury that is attached to the radiator which closes the relay when the radiator fins reach a certain temperature thus activating the fan. the fan even turns on after the engine is shut off when there is no more coolant circulating and combustion has ceased.

definetly a worthwhile upgrade. i'm very satisfied with how it turned out. thanks everyone for your help, it is much appreciated.

 

i agree with this completely.
if you havent replaced the fan clutch yet i can guarantee that is what it is.

the radiators in these trucks are tough, my truck was smashed in the front, broke all the radiator mounts off and smashed it up agains the fan and the radiator still worked great for almost 8 years, full o frust and all.

as for the electric fans, i feel it is worth it if you have the money just to free up that engine a little.

personally i would just stick with a cheap stock fan clutch

 

Since your problem is at idle/low speed, it would indicate an air flow problem, so I'd check the fan clutch. Since you stay cool when moving, it's very unlikely that you have a water flow problem (ie clogged radiator, water pump, t-stat). And I would argue in favor of keeping the stock fan and shroud. When you're at speed, the fan is basically freewheeling so you aren't saving much HP.

 

[QUOTE=alanbobalan;50477652]i'm seriously considering going with an electric setup because i do soo much stop and go driving and i plan on keep this bucket of bolts around for a while. i also plan on adding larger tires to my itty bitty 2wd pickup soooo an electric fan will vastly improve performance, mileage and cooling. i'm going to explore some junkyards over the weekend. i gotta act quick, there is too much aluminum in that engine for me to keep fartin around.QUOTE]

I know this thread is a couple months old (may help someone doing a search though)-but I got my electric fan at Auto Zone for $70. It's hooked direct to run whenever the key's on and I love it. A noticable improvement in HP. My little 4 cyl needs all the help they can get. Plus I *like knowing it's running all the time, I didn't want a sensor in it so that it only came on after a certain temp.

 

So if your key is on your fan is working?

I can think of a couple reasons why I wouldnt want to do that... one your engine will warm up much slower, espically in winter, two the motor will wear out very quickly at a constant run. The only time it needs to run regardless of the coolant temp is when the A/C is on.