2006 duramax overheating. Fan not coming on.

[AZ_Duramax]

Hi all,
Have been a member for a while, but this is my first post.

Just got back from a trip thru the Needles Arizona with 118 degree temps pulling a 18,000 5th wheel. Engine temps got high and trans overheat warning came on pulling grades. Easing up on the pulls controlled the situation, but the fan never came on.

I have searched the threads and have not seen this issue discussed.

Many talk of their fans coming on to often (Startup and at 210+ temps),
My fan is not coming on as engine/trans temps rise.

When I first got the truck, it was definitely known when the fan comes on (sounds like a jet taking off). So something has gone wrong.

Thanks,
Gery

[chevyburnout1]

If your towing that much weight and you don't ever hear the fan kick on it definantly sounds like your fan clutch went out.

[hcaliber]

fan clutch or restriction in thermostat, rad not heating up enough to kick in fan?

[AZ_Duramax]

Originally Posted by chevyburnout1

If your towing that much weight and you don't ever hear the fan kick on it definantly sounds like your fan clutch went out.

That is what i think is happening. It is a 2006 LBZ that has what appears to be an electrically controlled fan clutch (because I cannot see or feel the standard spring on the front of the clutch), I am trying to find out what to check out to determine what is causing it to stay off when the heat ranges are approaching the red zones and trans over heat is indicated on the DIC.

[chevyburnout1]

The clutch is still a manual viscous fluid clutch. Not electronic.

[Q101ATFD]

We need to clear a few things up:

First off, the fan clutch is just that - a fan clutch. There are no electrical controls for the fan, whatsoever.

Second, the fan clutch is setup so that it does not engage above approximately 45 MPH. So, on the highway, if you're going faster than 45, you're not going to hear the fan engage because it won't.

When you slow down and hear/feel the fan engage, your needles will drop almost instantly.

EDIT: chevyburnout1 you beat me to it as i was typing :o

[dwrat]

Originally Posted by Q101ATFD

We need to clear a few things up:


Second, the fan clutch is setup so that it does not engage above approximately 45 MPH. So, on the highway, if you're going faster than 45, you're not going to hear the fan engage because it won't.

:o

WHAT????????
You are 100% WRONG.
The fan will come on at any speed when it gets hot enough.
Sounds like you need a new fan clutch and that is most likely your only problem.

[Q101ATFD]

Originally Posted by dwrat

WHAT????????
You are 100% WRONG.
The fan will come on at any speed when it gets hot enough.
Sounds like you need a new fan clutch and that is most likely your only problem.

You got any proof to back that up before I look like an ass in front of my dealer?

I've had two of these trucks (6.0 and 6.6) that disengage the clutch at 45 MPH. Why else would there be a separate part number for the 4.10 and 3.73 differentials? They both worked fine at cooling at any speed below...

[Coolbreeze]

And a great ah ha comes up from the crowd.

I ran up a hill a few weeks going 63MPH and then slowed. Looked at the guages and they were fine, looked back down at them and the temp was at 230 uh oh--- guess I had to go less then 45 for it to kick on which it eventually did when I backed out of it.

[heymccall]

Originally Posted by Q101ATFD

The fan clutch is setup so that it does not engage above approximately 45 MPH. So, on the highway, if you're going faster than 45, you're not going to hear the fan engage because it won't.

This is definitely one you are gonna have to prove to me. The fan engagement is controlled by heat that thickens the "viscous" fluid within creating a "solid" (highly resistive) connection between the inner and outer hubs.

Some simple tests for the Original Poster.

1) Turning of the fan, by hand, on a cold engine (not running, of course) will have a feel of resistance (it will not approach freewheeling), as the fluid will have accumulated at the bottom of the hub.

2) Aggressive acceleration (1/2 throttle or better) on a cold engine should produce the fan whoosing sound. Some on here call it "morning sickness" http://www.dieselplace.com/forum/sho...rning+sickness

3) Inspection of the rear of the fan hub shaft should reveal that it is grease and dirt free. Loss of the "viscous" fluid is the number one cause of failure. That region (and the whole assy, for that matter) should be free of leaks.

4) And the final thing to check if the above is working is to ensure that the airflow paththrough the condensor and the radiator is clear.

a) A flashlight laid held inside the fan region (with the engine off, of course), at several different locations, pointing outward will confirm whether air can pass freely, and whether a cleaning is in order. Remember that there are voids between the condensor, aftercooler, and the radiator which can become plugged with debris over time.

b) Also, ensure that the plastic lower cover is in place between the bottom of the radiator and the front crossmember. When in place, you cannot see the fan when crawling under the front bumper.

c) Also ensure that the seal across the firewall that touches the hood is in place.

The above items create a low pressure zone within the engine compartment, to help to flow air through the radiator without the aid of the fan, meaning the fan will be needed less, and will ensure that the heat from the radiator will properly operate the clutch.