fan clutch always engaged

[chris989]

Hello all,

I have 1996 burb 7.4 4wd...

WE have had this truck for a while but now it is our daily driver. I noticed the fan is almost always engaged even under normal conditions. It is loud and it is killing my MPG.

Last year i changed the thermostat to a 180 after towing a trailer back from AZ. the truck would run over 215 with the towing and as designed I expected the fan to be engaged.

BUt now i have a 180 in the truck, it stays under 200 almost 90 percent of the time but the clutch is engaged.

Hayden tech says the clutch will begin to engage at 150 air temp. I live in Las Vegas, the pavement is 150 by 10 am.

Has anyone experienced this and does anyone have a better part # that might engage a little later???


Thank you,
Chris

[95 S_Trucker]

I would replace the fan clutch with a stock replacement. There is a chance the fan clutch has failed(it is 18 years old). I would look for a GM piece. If you buy a cheap aftermarket one, it will probably make more noise than the one you have now.


What kind of fuel mileage are you getting? I wouldn't expect anything better than 12 mpg.


And, your mileage will suffer when you put in a cooler thermostat.

[chris989]

Originally Posted by 95 S_Trucker

I would replace the fan clutch with a stock replacement. There is a chance the fan clutch has failed(it is 18 years old). I would look for a GM piece. If you buy a cheap aftermarket one, it will probably make more noise than the one you have now.


What kind of fuel mileage are you getting? I wouldn't expect anything better than 12 mpg.


And, your mileage will suffer when you put in a cooler thermostat.

It had a a hayden severe duty in it and i just installed a new one. I thought the original might be failing but there is not change.

[azdeltawye]

Originally Posted by chris989

… I noticed the fan is almost always engaged even under normal conditions. It is loud and it is killing my MPG.
…

You can recalibrate the cut-in temp of the fan clutch by tweaking the bi-metal spring in the front of the clutch assembly: Lift the outermost end of the spring from the two nubs on the clutch housing and rotate the spring and shaft to the fully engaged position (CCW for Hayden). Mark the position of the end of the spring on the housing for a reference. Continue turning the spring in the same direction until it yields slightly. Be careful not to go too far with this step! Let the spring relax and compare with your original mark. Repeat this until you get about ¼” away from the mark. This is much easier to do with the clutch removed from the vehicle BTW…

Install and take it for a test drive. Repeat as necessary.

Some fan clutches have adjustable spring mounts. I think Borg Warner might be one of them.

Good luck.

[chris989]

Originally Posted by azdeltawye

You can recalibrate the cut-in temp of the fan clutch by tweaking the bi-metal spring in the front of the clutch assembly: Lift the outermost end of the spring from the two nubs on the clutch housing and rotate the spring and shaft to the fully engaged position (CCW for Hayden). Mark the position of the end of the spring on the housing for a reference. Continue turning the spring in the same direction until it yields slightly. Be careful not to go too far with this step! Let the spring relax and compare with your original mark. Repeat this until you get about ¼” away from the mark. This is much easier to do with the clutch removed from the vehicle BTW…

Install and take it for a test drive. Repeat as necessary.

Some fan clutches have adjustable spring mounts. I think Borg Warner might be one of them.

Good luck.

Thanks for the info,

I forgot about this post, but here is my update. I switched back to the 195 stat. with a obd scan tool hooked up i now know 210 on my gauge is really ~196. With the 195 stat in place i think more heat is retained in the engine and out the exhaust and not put into the radiator and the clutch engages less often. Now that the weather has broke and we are under 100 it does make a huge difference in the engagement. I might try the spring tweek and lessen it some. I guess in the end I made it worse installing the 180 stat. Now that i know my gauge is off by 15 degrees i feel much better about the true temp.

Chris