Fan clutch operation question.

[turbo36]

First the car specs: 1965 Belvedere II, 383 mild mod, 3 core radiator with a shroud. I'm running a Hayden 2765 fan clutch with the 5 blade Mopar Performance fan, 180 degree thermostat and high volume water pump., it seems to not be working properly. At 75 degree air temp the coolant temp will run up to 215 at idle, 205 at moderate cruise speed of 35-40 mph but drop to 200 at a higher cruise speed of 55-60 mph. It appears to me to an air flow issue through the radiator.

If I stop the engine when it is in the 210-215 range and spin the fan by hand it freewheels with very little resistance . Is this normal operation?? My understanding is the clutch will slip until it get warm and then firm up.

thanks, Bob

 

[Dako]

I thought the idea of the clutch is to slip as rpms go up so as to draw less hp from the motor. Also, it is assumed that under normal operations you will have more natural airflow as rpms go up because you are typically traveling in a forward motion. As far as 'feeling resistance',...I never felt any when I had the stock unit on my `70 Duster 340 (wish I still had that car!), nor do I feel it on my `95 Dakota with the factory 318.

 

[turbo36]

I thought the idea of the clutch is to slip as rpms go up so as to draw less hp from the motor. Also, it is assumed that under normal operations you will have more natural airflow as rpms go up because you are typically traveling in a forward motion. As far as 'feeling resistance',...I never felt any when I had the stock unit on my `70 Duster 340 (wish I still had that car!), nor do I feel it on my `95 Dakota with the factory 318.

This is a "Thermal" clutch it is supposed to engage more as it heats up.

 

[Moparpwrstude]

Turbo, are you sure your radiator is flowing properly? should look like a whirlpool with the cap off and thermostat engaged. Hayden has an article up on fan clutches:http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Imperial/2007-imperial-fan-clutches.pdf

 

[67 coronet]

if you are sure it is a thermal fan clutch and not centerfugal,then it should have a very good amount of resistance when up to temp.a great test for a fan clutch is(when at operating temp)put a stick or something like a bar against the fan on the forward side of the rotation near the end of the blade.start the car and see if the fan pushes the bar out of the way,or if you can hold the fan still.if it moves the bar(with some good resistance)then it is good.make sure to leave room for the bar too move!dont pry against something,just free floating against the blade,held by hand.ya this is a bit dangerous,but not if you are carefull.its the only way to be sure of the clutch at speed.has to be done with two people,one to hold bar,one to start car.