Fan clutch engages at 90F

[Jbuntin]

I am having a problem where the fan clutch on the 8.1L engine engages intermittently at about 90F, and cycles on and off every couple of minutes. The engine temp gauge is about midway. This happens with or without the AC on.

I replaced the fan clutch this March; the old one added to the problem by remaining engaged at higher RPM, as when climbing hills...drove me crazy with noise. This is on a 31W chassis.

I wonder if the fan is getting enough air flow behind the radiator. Do the twin electric fans ever come on? I have yet to hear them, even in >100F air temps with the AC on.

[ARROWVP38]

you haven't heard the electric fans come on at all ? mine come on pulling a hill they cycle on & off as well as the fan clutch cycles have you started the motor let idle and warm up turn the a/c ( dash ) on the electric fans should cycle cool they condensor,trans cooler,help with the radiator cooling check the voltage at the harness connector to see if there is power to each fan if so then the fan motors windings are open and they need to be replaced. I'm in Phoenix Hilly and hot

[gauto5150]

Hmmm, you have a mechanical fan clutch off the water pump?
If you do, you must use an OEM fan clutch. Anything aftermarket usually makes your engine sound like a NASCAR it's so noisy. Especially the GM stuff, I had a 93 Suburban years ago and replaced it with an aftermarket style and it never seemed to unlock ever.

[max49]

I assume you're posted 90* was meant to be 190*. If the big belt driven roaring fans come on at 90*, you have a problem. If you're worried about your electric fans working, have your wife start the engine while you watch the fans, they should come on for a few seconds when u atart thew engine and again when you turn the engine off. If they do this, they probably come on after u have the AC running for a few minutes too.

[speed racer]

The fan clutch is designed to ingage and disingage at the temperature of the air coming through the radiator. If it is coming on and going off it is doing its jod. Any atempt to change this could harm your engine. That being said it is posible to remove the water pump mounted fan and install a large electric fan behind the raidiator and have it oporate from a thermal switch. The down side to this is you have to be very watchful of your engine temps because the viscuse fan clutch isn't doing it for you.

[dieselclacker]

The two electric fans in front of the radiator are there primarily for moving air thru the air conditioner condenser at low speeds, such as in city traffic. The big viscous coupled fan attached to the water pump and turned by the serpentine belt is temperature activated by the air coming thru the radiator core. Changing to an 180 degree engine thermostat made a dramatic improvement in the number and length of time the viscous fan engages on my 8.1 Workhorse.

[Jbuntin]

Thanks for your comments. I was indeed referring to the air temp being about 90F when the engine fan comes on. The engine has a new viscous drive fan clutch. I will check the electric fans at start-up as suggested, and give the 180F thermostat a try.

[edgray]

Maybe this info from the 2007 Chassis guide will help:

The main engine-cooling fan is mounted on the front of the water pump driven by the drive
belt and positioned inside a fan shroud behind the radiator. This engine fan is a variable drive
fan controlled by a temperature sensitive clutch. The clutch housing is a lightweight metal
construction that is filled with silicone oil and hermetically sealed. During periods of
operation when the radiator discharge air temperature is low, below 150 degrees, the fan clutch
limits fan speed to 800 - 1,400 RPM. As operating air temperatures increase, above 150 degrees,
a temperature-sensitive bi-metal coil tightens to move the sliding valve plate, allowing the flow
of silicone oil into the clutch chamber to engage the clutch, providing maximum fan speed.


Cooler and Electric Fan Assembly
When the main engine fan kicks in (very often when climbing an up-grade or when towing in
hot ambient conditions) a roar can be heard. The fan requires additional horsepower and can
even result in a downshift. Many owners mistake this noise as a transmission or engine
problem whereas it is normal operation.
The electric condenser fan(s) also assists with engine
cooling. The condenser fan(s) are mounted either on the
air conditioning condenser or on the transmission
external oil cooler. Both the condenser and external
transmission oil cooler are mounted in front of the
radiator. One large electronic fan was utilized on all
chassis prior to 2001 model year, and all chassis 15,000 lb.
GVWR or lower, or if equipped with a 6.5L diesel engine
regardless of model year. All other chassis 2001 model
year or newer will be equipped with two smaller electric
fans, see adjacent diagram. These fan(s) are controlled by
the Powertrain Control Module (PCM) and operate
whenever the dash air conditioning compressor is
operating or if the engine temperature is above 221

degrees F.

[MntDriver]

My engine fan will roar on when the outside ambient temperatures are 50 degrees! Of course it's when pulling these high altitude passes where we live, and also the thin air. Going across Monarch Pass this Summer, the engine fan roared all the way up, and most of the way down for about 30 minutes total....and that was without using the air conditioner, and outside ambient temps of 63-73F.

I also installed a 180 degree thermostat, and it decreased the roaring fan run times as my engine temperatures have decreased, while hopefully INCREASING my engine longevity.

[Jbuntin]

Thanks for all the fan info. The electric fans do engage when the AC is on. I will check to see if the 180 degree thermostat passes muster for CA smog checks. If so, that should take care of this issue!