14+ Possible Fan Clutch failure?

[Oilbrnr]

So I ran my truck pretty hard for three days on the beach in Mexico last weekend. Temps ran fine(210*-215*) and I could hear the fan cycle as you'd expect.

Last night I drove from Phoenix to my home in Flagstaff and I decided to do a MPG test and Cat Scale the truck (9,260) with the Four Wheel Camper which is now a permeant fixture. I typically see 11.8 mpg indicated on this trip and this time I was hovering around 9.5 which I thought was odd. When I was almost to Flag (30* outside) I happened to look at the temp gauge and it was lower than normal. I changed the EVIC to show the digital temp and it was 185*. I kept an eye on it, and it would rapid fluctuate between 185 and ~200. Once in town temps returned to the normal 210*.

I didn't hear the fan in the cab, so it wasn't like if the clutch had failed that it was fully locked. If the thermostat is faulty, I suppose running cooler it would have a somewhat richer mixture, though 185* used to be a pretty normal operating temp for engines in general.

Thoughts? Any of you guys had a clutch go bad? 69k currently on the clock.

Oh, and hand calculated mpg via GPS (odo was only off by a little over 1 mile in 146) was 9.2

[SimonandSimonBeast]

Let's see. 1 fan clutch on a '97 TJ. 1 fan clutch on wifey's '03 Trailblazer and 2 fan clutches on a '02 2500 Burb. Either I've had bad luck or beach riding is a bitch on these things (sand/salt air). It's been a while, but If I recall there was some intermittent weirdness before they had a full out failure sticking in the on position.

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[Bill2014]

Slightly lower engine temps typically translate into more power and will increase emissions! The increase in power will show as higher mpg. You saw something quite different so you probably had something else going on to shift your mpg.

I've never had a clutch fan go bad - but the parts stores sell them so they must
None of my vehicles from the '70's had clutch fans, they were direct belt drive - my '80's vehicles had non-thermal clutches on the fans. All my modern vehicles with transverse mounted engines had only electric fans (no clutch).

Now in this modern age, everything has to be more sophisticated and more expensive. And as a result, we have more parts to fail

[coder]

Here is an easy way to tell if your fan clutch is working correctly or not:

1) The fan clutch should stop spinning almost immediately when you shut the engine off, if it keep spinning the clutch is worn out.
2) With the engine off you should be able to turn the fan by hand, if not the clutch is locked up.

The fan clutch is a ware item I had to replace mine around 80k miles.

[RustyPW]

I've seen a couple of clutch fans go bad. Normally just lock up, and you can't spin them with the engine off. Seen 2 seized up at high rpm. One tried to go through the hood, and the other tired to go through the radiator.

[DamageWagon]

You can watch the fan at idle once it is warm and you’ve revved the engine to break the static hold and see if it is turning at engine RPM or slower.

[SimonandSimonBeast]

Also, look for any movement in the fan while off of course. You shouldn't be able to jiggle it at all. Also, look for silicone leakage on it. But, I do remember some period before full out failure that it stayed on more than it normally did during acceleration, especially after first start up. While it normally has some tension during "freespin" at speed and runs something like 1,500 rpm, it isn't too much a stretch that if it is starting to fail it could be getting more tension and running at a slightly higher rpm, giving you those results. It's cheap enough to replace it. Maybe your lucky and caught it before failure.

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[Oilbrnr]

I didn't have time to investigate it today. Ran it around town a bit, but haven't done a physical check yet. I just have a feeling it is the clutch as it would explain the dramatic drop in MPG.

[cb1987]

Thoughts? Any of you guys had a clutch go bad? 69k currently on the clock.

i think there was a batch of bad fans. my 16 had a bad one from day one. clutch was engaging when it wasnt supposed to. new replacement wasnt disengaging correctly either. i think it was just some type of malfunction of the viscous clutch. my 17 fan works perfect so im guessing there was just a small batch of defective fans

[Oilbrnr]

After some thought and investigation, I *think* the problem is the thermostat. I have a new assembly on order and will update this thread when I put it in.

[Bill2014]

After some thought and investigation, I *think* the problem is the thermostat. I have a new assembly on order and will update this thread when I put it in.

I was always suspicious of a faulty clutch causing your problem...

[Oilbrnr]

I was too, initially, but watching the temp gauge (and interior heater air temp) change extremely rapidly, kinda ruled out the viscous clutch. Besides, even if the clutch failed, a properly working thermostat wouldn't let the engine temps drop.

[waldo]

The fan on my 16 would sometimes roar for a mile or so down the road after a cold start. No rhyme or reason to it and it would eventually stop.

[olyelr]

The fan on my 16 would sometimes roar for a mile or so down the road after a cold start. No rhyme or reason to it and it would eventually stop.

Mine has done that many times before. However its been a while now that I think about it. Hmmm.

[DamageWagon]

That’s common in new fans. I’ve had it from OEM and Napa fans. I don’t think my Cummins has done it down to -5F though.

[Mule]

Did you get yours with the auto-eject feature?

[Oilbrnr]

My thermostat housing finally shipped today (16 days after order). I'll report back when I get it in.

[RustyPW]

Did you get yours with the auto-eject feature?

Did it damage the radiator?

[Mule]

Did you get yours with the auto-eject feature?

Did it damage the radiator?

That incident took out a lot of things.
Water pump, radiator, rad shroud, fan clutch, some wiring, power steering hoses...
Less than a year later, t-stat stuck...


Now (been ongoing for a while, but getting worse) the heater core's plugged and not working well...
Upside, I haven't blown up a water pump in a while.

[RustyPW]

Did you get yours with the auto-eject feature?

Did it damage the radiator?

That incident took out a lot of things.
Water pump, radiator, rad shroud, fan clutch, some wiring, power steering hoses...
Less than a year later, t-stat stuck...


Now (been ongoing for a while, but getting worse) the heater core's plugged and not working well...
Upside, I haven't blown up a water pump in a while.

I've seen one that chewed a nice round hole in the radiator core, about half way through on a cheby truck. Another was sticking through the hood of a Suburban.