When I pulled out of the lot this a.m., my cooling fan clutch engaged/disengaged within 2-3 seconds multiple times. Within 1 mile of driving, it stopped. Not warmed up, no A/C, just started today. Anyone out there have this happen to your truck? Everything "looks" clear.:confused:

normal- fan is heatsoaked on shut down, when you first start up fan will engage.

Sorry I didn't clarify. The truck has been sitting in the parking lot ALL night without running. I've heard the clutch engage many times before while towing and with high temps, but never while warming up in the morning.

Like blizzard said. There is no clutch but a fluid coupling installed on that fan. The fan always slips - 45...50 % when free wheeling and 5...10 % when "locked"

O.K. Not to be argumentative here, I have 19K miles on the truck, 6K miles towing. I've never had that WEERRR... sound kick in unless I were towing, exiting freeway under high temps, or the like. R/U telling me that everyone has their fan short cycle while driving the 1st 5 minutes of every trip? This is my first time at 70* and cold engine. Weird:confused:

There is fluid in the clutch. And, there are two chambers. One chamber has a closely spaced drive disc (the working side), and the other has nothing (the reservoir side). There are pumping vanes at the outside edge. They pump the fluid from the working side to the reservoir side using the difference in rotation speed. These vanes are directional, which is why fan clutches are directional.

The thermostat opens a valve that allows the fluid into the working side. This causes more torque transfer.

If you park it hot, the fluid leaks back into the working side. If you start it right up, it is quickly pumped back, but if it sits overnight, the fluid gets thick. On a cold restart, the working side has thick fluid in it and you get coupling. After enough slipping, with the valve closed (cold), the fluid is pumped back to the reservoir side and it releases.

The more it's working, the less it slips, and the longer it takes to pump out the working side...that's why it seems to cycle at higher loads. At partial slip, there's more slipping, and more pumping, so it's got a smoother transition, and you don't get the cycling.

They all do this, and it's normal.

Thanks guys..."I'm not worthy. I'm not worthy..."(Wayne's World)

Not to worry my 2004.5 has done this ever morning winter and summer the truck has 13k. First couple of miles then acts normal. Had the same thing on my 93 gasser 454. When towing heavy load on hot days it works perfectly.

Steve

Yep just the same here. Mine just does it for about a half mile.

Just takes time and RPM to pump the fluid out some times. Remember, the fan clutch is our friend...

There is fluid in the clutch. And, there are two chambers. One chamber has a closely spaced drive disc (the working side), and the other has nothing (the reservoir side). There are pumping vanes at the outside edge. They pump the fluid from the working side to the reservoir side using the difference in rotation speed. These vanes are directional, which is why fan clutches are directional.

The thermostat opens a valve that allows the fluid into the working side. This causes more torque transfer.

If you park it hot, the fluid leaks back into the working side. If you start it right up, it is quickly pumped back, but if it sits overnight, the fluid gets thick. On a cold restart, the working side has thick fluid in it and you get coupling. After enough slipping, with the valve closed (cold), the fluid is pumped back to the reservoir side and it releases.

The more it's working, the less it slips, and the longer it takes to pump out the working side...that's why it seems to cycle at higher loads. At partial slip, there's more slipping, and more pumping, so it's got a smoother transition, and you don't get the cycling.

They all do this, and it's normal.

Now that is really a nice explanation how the fluid coupling works....like that one!

Sorry I didn't clarify. The truck has been sitting in the parking lot ALL night without running. I've heard the clutch engage many times before while towing and with high temps, but never while warming up in the morning.

This is pretty common on viscous fan clutches. Until the silicone fluid gets redistributed, fan engagement on initial startup is common and normal. Mine does it about 1/3 of the time. It seems to be somewhat outside temp sensitive. Does it most in spring and fall when overnight temps are in the 60's. Doesn't do it when it is very cold at night. My S-10 and full size van did the same thing, just the nature of the beast