Hi all,

Been having a problem with my '99 7.4 (big block) running too cold, usually well below 180. This seems to cause the 'burb to get worse mpg than it should. It was suggested I swap out the t'stat to a 195, so I recently did, no change. In talking to a mechanic (pro) I know, we noticed the air behind the fan was cold, really cold. Then we noticed the fan was turning when it should not be.

Anyone have similar experience? I want a bit more input before I spend the $$ on the fan clutch. Should it stop turning at some point?

Thank you,
Larry

 

was the mechanic a ford tech. when a ford clutch fan disengages you can see it...not so for chevy clutch fans. Chevy fans appear to be turning all the time.
if you think the fan clutch is the issue; run the engine for a brief time with the fan clutch removed to see if it comes to temp or remove the fan shrouding to make the fan less effective.

 

I currently have the same deal with my truck. if the truck is cold, the fan rpm will not be close to what the engine rpm is.

If it's cold you can go out there and try to turn your fan and it's hard to turn your clutch is bad. it should spin freely.

if you listen close you can hear it too.

 

L5wolvesf: Welcome to the forum.

I'd pull the t-stat and make sure it opens and fully closes in boiling water. Even if it sticks open about 1/16", the engine will run cold.

 

Or stick a piece of cardboard in it.

 

even better

 

That was going to be my suggestion too, when its loaded you hear it moving air, when its not, its much quieter...but still spinning

 

The fan is not the problem. The t-stat should still regulate the temp. even if the fan runs full speed all of the time. The only reason for fan clutches was to reduce load on engine and thus improve mpg. While blocking the radiator may elevate the temp., it's covering up the real problem

Another thing to check would be the accuracy of the temp gauge.

 

General mechanic.

 

I can turn it, but it won’t spin freely