Fan clutch locking up

[Jimmy9190]

I put a new aftermarket fan clutch on my Dakota 6 months ago. No problems with it then. Now though if I sit idling, like at a red light that takes too long or at a slow drive-thru window when I get moving again, the clutch is locked up and my engine has the loud howling noise from the fan clutch. Then I have to drive agressively and run the RPM's way up for half a mile or so to disengage the fan clutch. The fan clutch will howl for the first 1/8th mile or so when I get started in the morning when my truck has sat overnight too.

Is this a normal characteristic of a fan clutch, or should I try to get a warranty exchange on it? The one I bought has a lifetime warranty. I have never seen a clutch lock up after idling like that though. I wonder if it is temperature related now that hot weather is here again.

Thanks for your help here.

 

[jstutz]

This is interesting because my blazer does the exact same thing.

 

[Chris142]

It's working like it should. It's job is to pull air at at high temps or slow speeds. Once moving it takes a minute or so to unlock which is normal.

 

[Jimmy9190]

Thanks for the quick replies. I thought it was OK. It's just strange because my old factory one didn't do that. But the factory clutch was probably worn out long ago.

 

[Food Scientist]

A lot of fan clutches will engage when the air conditioner is on, especially at low speeds.

 

[The_Jeff]

Originally Posted By: SVTCobra
A lot of fan clutches will engage when the air conditioner is on, especially at low speeds.


But how do they know? They just feel heat coming back from the rad/condensor. No way to force them.

Of course, more heat from the condensor means it's more likely to happen. But it's not like cars with electric fans that get a computer signal.

 

[40Deluxe]

It is the combination of the thermostatic coil or spring located on the radiator side of the fan hub and the fluid that is inside the fan hub

 

[Brian Barnhart]

40Deluxe is correct.

Fan clutches respond according to the air temperature around them. They don't "switch" on or off, but engage more fully as the temperature rises above a certain point.

They contain a high viscosity fluid that settles to the bottom of the housing when the engine is off. Following a cold start, the fluid must be distributed within the clutch by rotary motion, and it is partially engaged during this distribution. That is why there is alot of fan noise after a cold start, regardless of outside temperature.

These clutches usually fail from loss of fluid and will generate little fan noise at that point. Therefore, a replacement may seem noiser than the previous clutch if it suffered fluid loss. Variations from unit to unit can also occur due to the design temperature and the initial amount of fluid inside the clutch.

 

[bullwinkle]

The excess heat from A/C use & standing still will cause clutch lockup until it cools from moving. My diesel E-350 actually has an electric clutch that comes on when going highway speeds when towing uphill in hot weather to cool off the ATF-apparently helps a lot too, the abused transmission now has over 203,000 miles with no major problems!

 

[Jimmy9190]

Thanks everyone for the info here.,I had an idea that the clutch was OK, just either more sensitive to heat or in better working condition than my original fan clutch. Or both.

Gotta love BITOG. Thanks.

 

[firefighter]

Your fan clutch is working but not properly. The OE ones release much faster. For example when you start your truck in the morning the clutch should not be locked for an 1/8th mile. I don't think it will hurt anything maybe a little fuel milage, but probably nothing you will notice. Just my two cents and the stuff like this I see in the shop everyday.

 

[mechtech2]

It sounds like it is working OK.
Maybe engaging a bit early , temperature wise, but actually quite normal.

 

[Chris142]

Originally Posted By: eljefino
Originally Posted By: SVTCobra
A lot of fan clutches will engage when the air conditioner is on, especially at low speeds.


But how do they know? They just feel heat coming back from the rad/condensor. No way to force them.

Of course, more heat from the condensor means it's more likely to happen. But it's not like cars with electric fans that get a computer signal.
The pressure in the high side of the Ac puts out nearly the same temperature. So If you have 300psi On the high side coming off the condensor you will have 300degrees coming off it too. That 300 degrees activates the thermal spring which turns the vanes in the clutch which makes it lock up and spin faster.

Fan clutches slowly lose their efficiency so you dont notice it. Then when you put a new one on you can hear the fan and you think it's loud.

 

[RiverWolf]

Jimmy, except for the 1/8th mile cold, that behaviour sounds like my OEM 4Runner fan even after 70K miles. With the current 90°+ heat we're having, I hear the fan stay locked up until around 2,000 rpms where it finally calms down when pulling away from a stop. At lower ambients, I don't notice it as much. As suggested, maybe the replacement fan is slightly more aggressive in operation or maybe the blades have a different pitch making their engagement more noticeable.

-Brent

 

[Jimmy9190]

Yeah, I am not too worried about it now. This is the first aftermarket fan clutch I have owned and it kicks in a lot more often in summer I guess.