if not I'm very concerned about the future
1977 Mechanical Fan Question
Thread Starter
Instructor
Joined: Jan 2011
Posts: 221
Likes: 1
From: Sylmar CA
1977 Mechanical Fan Question
Okay I have a question about my mechanical fan on my '77. I heard mechanical fans have some sort of spring system so that if the fan gets stuck that it keeps rotating to ensure that the mechanical water pump also keeps working. Am I supposed to be able to stop the fan by hand when the car is idling? Is that normal or is my fan faulty and need to be replaced? It might be a stupid question or not but I'm wondering. Any help will be appreciated.
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Keep your hand out of the fan!! or lose it. There is a clutch (the silver thing facing the radiator) mechanically mounted on the fan that engages and disengages based upon temperature of the air flowing throught the radiator. Sometimes it looks as if it is free wheeling as it has "decoupled " and is slow, but still turning.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 221
Likes: 1
From: Sylmar CA
I was just curious and wondered if I could stop it by slowing it down with my hand and eventually was able to just hold on to it after slowing it down and even throw it backwards. Its still operating that way its supposed to right? like as long as it is running on its own with the engine its all alright?
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
Keep your hand out of the fan!! or lose it. There is a clutch (the silver thing facing the radiator) mechanically mounted on the fan that engages and disengages based upon temperature of the air flowing throught the radiator. Sometimes it looks as if it is free wheeling as it has "decoupled " and is slow, but still turning.
It can take your fingers off! 
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
The old trick with BMWs was to fold up a newspaper and if you could stop it with that, the fan clutch was bad. Yours is obviously bad, but never use your hand.
An easier way is to see if it spins when you shut the engine off hot. It should stop almost immediately.
Also with the engine off and hot, you should not be able to spin it.
An easier way is to see if it spins when you shut the engine off hot. It should stop almost immediately.
Also with the engine off and hot, you should not be able to spin it.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
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From: Butler Pa
Melting Slicks
Joined: Aug 2010
Posts: 2,487
Likes: 10
From: Palm Beach Florida
St. Jude Donor '12
NEVER PUT YOUR HAND OR FINGERS IN OR BY THE FAN if you wish to keep them!! Would you stand in front of a prop on a plane and try to stop that too.... If you can spin the fan AFTER the car has been running/warmed up and the fan spins freely more then 2 revolutions then the clutch is going.
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Le Mans Master
Joined: Mar 2008
Posts: 5,948
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From: Oxford MA-----You just lost the game!!!!
What I like to do is to lean over the fan shroud and stick my tongue into the fan. If I can stop the fan with my tongue, the clutch definitely needs to be replaced. I especially like doing it in front of my little nieces and nephews, because it's imitatable!!!
Pelayo114, I'm just bustin' your chops, it's not a stupid question, lots of people are kinda confused about how clutch fans work, probably because they don't really make cars with them anymore. I think some trucks may still be made with them. Anyway, keep your fingers out of the fan! Good luck with you fan clutch replacement, it's a pretty easy job. Just remove the fan (4 nuts) take the clutch off the fan, bolt the new clutch on, and replace the fan. Might as well spiff up the fan with a fresh coat of black satin spray paint, while you're at it. See ya,
Scott
Pelayo114, I'm just bustin' your chops, it's not a stupid question, lots of people are kinda confused about how clutch fans work, probably because they don't really make cars with them anymore. I think some trucks may still be made with them. Anyway, keep your fingers out of the fan! Good luck with you fan clutch replacement, it's a pretty easy job. Just remove the fan (4 nuts) take the clutch off the fan, bolt the new clutch on, and replace the fan. Might as well spiff up the fan with a fresh coat of black satin spray paint, while you're at it. See ya,
Scott
