Fan clutch question

[Sunliner]

I'm checking the fan clutch in my 97 Blazer..
Turning it by hand, the fan turns with just a little resistance-no freewheeling-while the shaft stays put. From what I've read elsewhere, this is normal.

I tried the dynamic test in the Haynes manual & noted that as soon as I start the vehicle, the fan and shaft both turn consistent with engine speed & stays that way. Does this indicate that the clutch is bad?

Overall, seems that the engine is running a little cooler than it should, wondering if the fan is going all the time.

-Mike

[Teal95Jimmy]

if the engine is cold, the fan clutch should allow the fan to rotate with little resistance. when the engine is hot (i dont remember the temp) the fan should be very hard to turn

[OverBoardProject]

I had a college mechanics instructor that told us to use an old rotten rad hose to test the fan.

With the motor running touch it to the fan lightly, and if the engine is still cool it should stop the fan. This won't work untill the fan clutch has warmed up.

And when it's hot where the fan should be on touching the old rad hose to the fan should not stop it.

Be very carefull if you try this. Wear a face mask.

I've basicly only worked with e-fans so I've never tried it.

[muzzy1maniac]

Don't try this!!! That is ridiculous!! The risk of injury isn't worth it!!!! Use the test methods found on this board. If your turck is running cool( you never gave us any real numbers) it's probably your thermostat starting to fail.

[Sunliner]

It usually runs with the temp no more than one or two ticks above the hashmark midway between 100 & 210 (guess this would be about 160-170?)

I had always heard it was supposed to run just short of 210 deg & that's about where it used to go. It's only a few "ticks" off, so maybe nothing is really wrong. I do have relatively new coolant in the system.

I checked the guage-it was good & replaced both the thermostat & the temp sending unit. With ~121k miles on it, I don't feel too bad replacing those kinds of things either way.

I think what I'm missing is telling the difference between when the fan is just spinning along with the engine versus actually being "on".

I tried manually spinning it just after running for a while, versus spinning it dead cold, & can't feel a difference in resistance. There's always some resistance.

Thanks guys

[rksnc]

The fan isn't your problem. I would change t-stat. Make sure you install proper t-stat. May need to hook up scan tool and see what computer is seeing. Maybe sensor not correct for the gauge, or put temp gauge in radiator and check temp there.

[old_master]

When the clutch is cold the fan should turn relatively hard, as the clutch warms up the fan turns more freely. When the ambient temperature is below 35 degrees F and the engine is cold, it's very easy to tell when the clutch warms up: when you start the engine, you will immediately hear a "roar" from the fan, as the clutch warms up, it engages and the "roar" is less noticeable. This “roar” sound comes and goes as the clutch and engine warm up. With sub zero ambient temperatures, and or a faulty thermostat in the engine, the clutch may take several minutes to engage, or may not engage at all. Fan clutch temperature is totally independent of engine temperature however if the clutch is disengaged it will cause the engine to run slightly cooler, and the fan will "roar". The purpose of the fan clutch is two fold: Reduce the “roar” and drag on the engine at normal operating temperatures, and also to provide air movement across the radiator when the engine is at lower rpm and or vehicle speed. When the engine has achieved normal operating temperature, air is drawn through the radiator, heated by the coolant and across the fan clutch. This warm air, along with heat generated inside the clutch itself by slipping, keeps the clutch engaged. If the engine is operated without coolant, eventually the engine will overheat and the warm air heated by the coolant from passing through the radiator obviously is not present, the fan clutch cools, the clutch disengages, the fan “roars” and attempts to cool the engine. (That is inherent with the design and actually does very little to prolong overheating.) Under normal circumstances and when all systems are operating properly, the fan clutch should be fully engaged by the time the engine reaches operating temperature. There are specifications for the fan clutch and precise ways of checking its operation, one of which utilizes a piece of reflective tape attached to the fan clutch and using a special tachometer with a built in strobe light, much like a timing light.

There are some obvious, and some not so obvious reasons for incorporating an electric cooling fan. Electric fans operate "on demand" and only run when engine coolant temperatures demand additional cooling. By using an electric fan, there is a certain amount of engine horsepower gained due to the fact that the engine doesn't have to expend energy turning the mechanical fan. It also saves wear and tear on water pump bearings/bushings because there is less stress on the pump shaft. Electric fans obviously have sensors, wiring, relays, fuses, etc increasing installation and maintenance costs. Electric fans increase alternator demand, but that amount is negligible. With front wheel drive vehicles that have transverse mounted engines, there is no choice on which cooling fan system to use, whereas with rear wheel drive vehicles, there is a choice.

[Fyter87]

You can always take a timing light up to the fan. You can tell when the Clutch is engaged or not. Plus when the fan cluth is engaged the fan makes a roaring noise.

[BlazerLT]

Sunliner,

Your fan is fine.

[bobpombrio]

Or you could do what I did and just remove the fan and clutch and replace with an electric fan. It's not hard to do and the electric fan pays for it's self after a few tanks of gas. Oh yea! Can you say increased HP? I knew you could...

At the time I did this I also put a K&N cold air induction system on mine which also helps. So I can't tell you exactly how much HP you get back, but I know it's more than 20!

Bob
2000 LT with 190K+ miles and still going strong.

[BlazerLT]

There are no huge gains from removing the stock fan assembly, it essentially free wheels with no drag on the motor when reved at anything above idle.

[wolfox]

Indeed, where do you think the electrical power comes from to drive electrical accessories?

If you don't want to think about it too long, here's an interesting read:

http://www.aaroncake.net/rx-7/efanmyth.htm

Most of the data supplied is in the light of Modifying your Mazda RX-7, but the core principals are the same. Unless you use your head and build/put together from kit a "properly matched" cooling system, it's really of no benefit to switch a vicsous clutched mechanically driven fan for an electric. There are some subtle exceptions. Some people here have had great results with using junkyard e-fans from Taurus cars and wagons. They *work*, there is no denying that. But calculate how much power it takes to turn those fans, if they can sustain high CFM when cooling system "boosting" is needed in hot weather when you roll off the highway to stop and go traffic - and if it can keep up with demaind of A/C thermal loading when the vehicle sits idle. Remember, you do not get something for nothing. The electricity needed to turn the e-fan in certain situations can cost more loading of the engine via the alternator and battery subsystems to the point where they present no advantage at all. And if you seriously offroad, forget about those fans turning when slopped with mud or water touches the edges of the fins. You don't hear of this happening to clutch driven belt fans too often.

My Scooby running off of e-fans would overheat on deep water and muddy terrain runs. The dual e-fans would load up with crap and not turn anywhere as fast as needed. My Jeeps, trucks and my Blazer never suffered from this problem at all. E-fans work great in street applications, but a truck that sees offroad and wet crossings should never see one placed under the hood. Oh, and one last parting shot....Flex-Fans are a severe no-no. Tried one under the hood of my CJ and Wrangler, both carrying 4.2 liter Ford Slant-6 inline engines. These fans can fracture like grenades under high RPM loads, nor do they cool as efficiently because as engine speed increases, they flatten out to having no rake at all. God forbid you get one near mud too especially on the older Jeeps with no fan clutch. The second they are introduced to anything other than air, they break.

Ummmm, back to your regularly scheduled shizznat...

[OverBoardProject]

There is 1 place where an e-fan works better in deep water.

You can turn them off for deep water crosings where a conventional fan might be bent into the rad.

I do a lot of crawling with my trailerr (carring my boat and accessories) and the e-fan keeps my motor way cooler. I only have to contend with dust and rocks in those situations

[wolfox]

If you approach deep water crossings properly in a clutch/belt driven fan equipped truck, the tips will only spang and clatter occasionally on the water as it does trough around and behind the front bumper - keeping things clear for the most part. It's when they ingest a good lump of mud that things can get a little scary. But the clutch/belt driven fans will gracefully self-clear. A gooped up E-fan just lopes and wobbles along at half speed.

For the record, are you using an E-fan on an S-10 pickemup, or a T-10 4x4 Blazer? And what's your engine displacement?

(Edit: Nevermind - I read your profile, basically your signature! 4x4 Blazer assumes 4.3 liter engine)

What kit did you end up using in setting up the e-fans in your Blazer rig? If cobbled together, ghetto style and home built, please - list a few details, like the type of fan used, current draw, CFM and wether or not you use pushers/pullers directly mounted to the radiator or converted the fan to work with the existing shroud under the hood. (I have been most curious and trying to gather up info for my own files - especially when I heard folks are doing wonders with Taurus e-fans on Blazers with light mods)

[blazee]

His sig says it's an 85, so unless it's been modded.... it's probably a 2.8.