My old fan clutch was worn. It had a little play in the hub, it leaked a little, and it continued to spin for a few seconds after I shut off the engine. The car never overheated, but the fan clutch was obviously worn.

Anyway, I changed it to a new one, and now the car sounds like a Cessna 152 when I rev it above 3000 rpm! I can definitely hear the fan roaring when I rev the motor. Is this normal? Can I change to a flatter pitch fan to quiet it down. Like I said, even with the worn clutch, the car ran very cool. Thanks, Fellas!

Temvette72

 

72,
I have the same noise with mine. 74w/350. I think it just goes with being new. Only time will tell. glassman74

 

Just replaced my fan clutch about 6 weeks ago. I don't hear any additional noises, even abouve 3500 rpms. When the engine is cold, the fan turns (after I turn the engine off) about 1 1/2 turns....when the engine is hot and I turn it off, the fan just stops turning. FYI

 

What kind of fan clutch did you buy,was it a thermostatic type ? It should not roar when its cold except for the first few seconds until the silicone heats up.

 

It's thermostatic. I installed it when the engine was quite warm and took it out for a test immediately. I will let the car cold soak and see how it behaves.

Thanks,

Temvette72

 

Very same thing happened to me, except on my 65 Buick Riviera. Replaced a bad fan clutch and I thought I was behind the stick of an F-16 !! drove it like that for a couple of months and yanked it off, sent the old one out to be rebuilt, put it back on and never heard a peep out of that ole nailhead again.
Never did figure out what made that new clutch sound so loud.

 

Check & see if the fan still spins a turn or two at shutoff. When my original fan clutch went south it locked up solid. I was on the interstate when it happened and the roar that started up really got my attention...

 

I was told that if it turned after the engine was shut off more than just a little bit that it had to be replaced. My old one spun down for 2 or three seconds after I shut it off. The new one stops spinning almost immediately. It doesn't matter if it's hot or cold.

Temvette72

 

replaced mine 3 weeks ago. was loose and leaking and the first 1/4 mile or so its sounds like you describe. actually make the car sounds tougher!

 

It actually makes mine sound like a UPS truck....A nice sound when you're waiting for parts, but not so nice otherwise! I swapped back to my old one. I am going to see if they carry a non-thermostatic clutch at my parts house. Hopefully, that will be quieter.

Temvette72

 

The non-thermostatic disengages due to rpm. Your thermo clutch should disengage when the engine is cold and engage when hot. I think it was bad.

 

How do you tell one type from the other? PG.

 

The thermo type usually has a coiled spring on the front towards the radiator. The non therm doesnt have anything on the front side,its just plain/flat.

Here is some info on different clutches.
Non-Thermal Fan Clutch
• Low cost alternative for some standard thermal clutches.
• Always engaged, less fuel savings than a thermal clutch.
• Spins at about 30-60% of the water pump speed.
• Shorter life expectancy.
• Cannot replace a heavy-duty clutch.
• Identified by the smooth, steel faceplate, (without a thermal spring assembly), on the front.
Thermal Fan Clutch
• Varies the fan speed with temperature of the air behind the radiator.
• Engaged (high speed) operation provides maximum cooling.
• Disengaged (low speed) operation provides fuel savings and noise reduction.
• Greater life expectancy than a non-thermal clutch.
• Briefly engaged at cold start-up.
• Engages at about 170° radiator air temperature, (about 30° lower than coolant temperature).
Standard Duty Thermal
• Turns fan 60-70% of shaft speed when engaged.
• Disengage to 20-30% of the shaft speed
• Used with lighter pitch fans. (1-1/2” of pitch).
• Flat plate impeller design with 11.4 Sq. In. of working surface.
• Identified by a smooth steel faceplate & thermal spring assembly on the front side.


Heavy-Duty Thermal ….. Corvette AZ GM # 372502
• Turns the fan 80-90% of the shaft speed when engaged for increased cooling.
• Turns the fan 20-30% of the shaft speed when disengaged.
• Used with deeper pitch fans. (2 -1/2” of pitch).
• Land and groove design with 26.0 Sq. In. of working area allows higher operating RPM’s.
• Identified by finned aluminum faceplate and thermal spring on the front.


Severe Duty Thermal …..Corvette AX old-GM # 343721 new-GM # 88961768
• Turns the fan 80-90% of the shaft speed when engaged.
• Turns the fan 20-30% of the shaft speed when disengaged.
• Used with deeper pitch fans. (2 -1/2° of pitch).
• Land and groove design with 70 Sq. In. of working area.
• Larger working surface provides cooler running and longer life expectancy.
• Thicker body and deep finned faceplate dissipate more heat.
• Can be used in place of many heavy-duty clutches.

Here is a link to the full page.
http://www.haydenauto.com/Featured%2...s/Content.aspx