Engine Fan Always On

[lone_star_dsl]

I was running around town this morning and for a brief moment, I turned the A/C on to quickly cool down the interior.

As I was pulling out of the parking lot, the engine fan came on, which I fully expected. After a few minutes, I turned the AC off but the fan continued to run.

I made another stop, shut the truck off and ran inside. 10-15 minutes later, I started up the truck and noticed the fan came on again.

My drive home was about 20 minutes. It is all highway with no stoplights. The fan ran the entire time. I could hear it almost shut off but then it seemed to come back and run faster.

The outside ambient air temps were 60-65 and I was not towing or stuck in stop and go traffic. I checked the coolant level and oil level and they were all fine. The dummy temp gauge didn't move at all.

Whats going on here?

 

[JLDickmon]

sticky relay maybe?

 

[Tail_Gunner]

If I understand, you are refering to the cooling fan behind the radiator.

There is only two things that will cause that thing to kick in-
1) A lot of heat coming thru the radiator causing the fan clutch to engage the fan-- or
2) A bad fan clutch that engages too soon or will not dis-engage fully at cooler temps.

You need to verify that the engine is indeed not running hot. Is the coolant level full? Is the t-stat functioning properly? Any kinked or restricted coolant hoses?

Unless you can find a reason that would cause the engine to be running hot, replace the cooling fan clutch.

Unless the outside temps are high and you are towing something, these trucks have enough cooling capacity where you should never hear the cooling fan when just plain cruising.

 

[lone_star_dsl]

I went out this morning and tried to spin the fan by hand. It was extremely hard to turn and seemed to make a "grinding bearing" sound.

I had to run around town for a while this morning and the fan finally shut off.

I got to a parking spot and turned the fan by hand. It rotated normally with only the normal resistance and sounded just fine.

Now I have no idea whats going on.

 

[DaveBen]

I would keep an eye on it and drive it normally. You won't do any damage to your truck by keeping it too cool, other than it won't run as efficiently as it would at a hotter (normal) temperature. The fan is controlled by the ECT (Engine Coolant Temperature) sensor, but I don't have the books on your truck so I can't tell you where it is.

Dave

 

[Tail_Gunner]

---- The fan is controlled by the ECT (Engine Coolant Temperature) sensor, but I don't have the books on your truck so I can't tell you where it is.

Dave

On my 7.3, there weren't any electrical connections to the fan clutch when I pulled it to R&R the water pump a year ago. There is a metalic coil on the clutch that senses temperature and engages/disengages it as appropriate.

 

[DaveBen]

Excuse me TG. I was thinking of the 6.0 and I knew he was not running a 6.0. Brain fade.

Dave

 

[Tail_Gunner]

Excuse me TG. I was thinking of the 6.0 and I knew he was not running a 6.0. Brain fade.

Dave

Been there!!

 

[BIG JOE]

Just my .02 but with the grinding~bearing feel to it.. intermittent on/off, more On, than Off.. on a 8 year old Fan Clutch.. (with Winter Snowplow use).. It's probably time to just replace the (worn out) Fan Clutch (?) Lone Star.

As I've always understood it: On a cold start, the fan will be engaged, until a given temp is reached, as sensed from the WP shaft. It then Disengages. When shaft temps reach a given Higher temp.. a Thermo-mechanical spring clutch affair.. Engages it. Reverse happens when temps cool. Maybe the "Thermo" capabilities are Shot ? Correct me if I'm wrong guyz ?

Joe

 

[Tail_Gunner]

As I've always understood it: On a cold start, the fan will be engaged, until a given temp is reached, as sensed from the WP shaft.

That would agree with what I've experienced. I've heard it kick in when the engine is cold and then slowly dis-engage after a few seconds.