Fan clutch

[westport70]

Can someone tell me how to tell if the fan clutch is shot? No slop or any thing just wondering. Also i am on the 3rd set of oil coolant hoses in 300k miles is there some thing i need to know aboyt these?

[More Power]

Normally, and when cold, the fan can be rotated with some resistance - due to the drag of the viscous fluid inside the fan-clutch.

Ordinarily, the fan-clutch should engage when you're driving stoplight to stoplight in town on a hot day and you have the A/C on. The fan will roar between stoplights. If you have somewhat normal hearing, you'll hear it.

Otherwise, the fan-clutch should engage (roar) whenever the engine coolant temperature exceeds about 210 or so, like while towing or pulling a grade. There is some variability in factory clutch engage temps.

Jim

[rameye]

Have never ever heard mine....I have the Kennedy set up.

Always wondered if it was working..

[16gaSxS]

Have never ever heard mine....I have the Kennedy set up.

Always wondered if it was working..

Maybe you have not gotten the engine hot enough to engage it. The other thing that affects it is the amount of hot air going through the radiator. I you have a bunch of junk between the A/C condenser and radiator then not enough hot air is getting through to heat the clutch up so it won't engage until higher engine temp. I have noticed that when I clean the radiator out that the fan engages at lower temps.:)

[Billy V]

The Kennedy Fan Clutch is a great mod. I installed it years ago and it has worked for me many times climbing the hills in the Sierras.

It cools the motor down fast.

[rameye]

I clean it regularly...(the space)...still never heard it....and yes I have gotten it to 210 and never heard it engage.

Wondering if the original radiator just isnt exchanging heat properly...original equip circa 1995. Doesnt look bad when I eyeball the inside..

go figure.

[AllThumbs]

Radiators are mysterious contraptions to me because you can see so little of them and they can be pretty bad without showing it. One check of the health of your system is to see how the heater works. If the heater core is gunked up, the radiator probably is too.

[rameye]

Heat from vents is Africa hot!

I flowed it (radiator) once when I pulled the motor...spit out all the water on the bottom as fast as it went in on the top....I always thought that was a fair sign of health.

This has been a 10 year mystery...I'll will keep at it.

[Robyn]

The radiator can allow water to pass through real quick, but still not be in good health.

As the time ticks by, the inner surface of the tubes get coated with a layer of insulating CRUD that keeps the coolant from touching the aluminum tube itself.

Once this happens the radiators ability to shed heat drops off a BUNCH.

Also over time the outer fins can become somewhat cloged with dirt, bugs and other debris.
These factors result in a dramatic loss in cooling ability.

Also the AC condenser can become partially clogged with bugs and stuff that also block airflow.

The space between the condenser and the radiator also collects debris.

Now the fan clutch on these rigs was set to come on at a far too high of a temperature setting.

Back in the mid 80's GM had it figured out well and the fans on the Burbs and pickups would come on at about 210 and roar like crazy on any hill of consequence or while in slow traffic.

These things made a Helluva Howl and so what happened, the owners whined up a storm and bitched and complained that it was too noisy.

Soooooooo Gm raised the temp settings on the fan clutches to eliminate the bitching.

This caused a buttload of issues and has helped fry a lot of good engines.

The fan clutch used on the 6.5 will not come on generally until the gauge reads 215 to 220F

This is way too high. The cooling system on these rigs is on the marginal side anyway and with this high fan clutch setting just will not allow for proper cooling.

The JK fan clutch is the only real good way to fix the issue.

The electric fans are a joke and just dont move the volume needed to cool these things.

I have thought about and worked on several Ideas.

Horton made an electric fan clutch that was workable, but there was a need for a switch that was tied into the AC system to turn engage the clutch when the AC high side pressure came up to allow for proper cooling.

I could not easily do this without major mods to the AC system, so this project is sitting for now.

Go with the JK fan clutch and your cooling issues will pretty well go away.

Now a radiator with 100K plus on it should be considered, USED UP and replaced with a fresh one.

Visteon makes an OEM quality radiator for these that is priced at about $230

Stay away from the no name big box store replacements. These units are mostly made overseas and the tubes are epoxied into the header plates.

Once the epoxy cracks (and it will) the radiator is junk.

The HO water pump, dual stat conversion and the JK clutch should be considered a mandatory "things to do" if you are going to tow anything much with a 6.5 truck.


Missy