trsulliv

Can somebody tell me how to determine when a fan clutch needs to be replaced? It is on a SB engine and is the orginal clutch. It does not turn very freely when the engine is off, maybe 1/2 revolution.

Also, what happens when it doesn't work?

Does somebody make a spacer to replace it, or should I replace it if it is bad? If I replace it, who has a quality unit?

Peterbuilt

Start with a cold motor, turn on car for 2 minutes then shut it off. See how much resistance it takes to turn the fan by hand. Turn on motor and run untill it's hot (10 to 15 minutes) turn off motor, there should be more resistance to turn the fan when hot. Also fan should stop within 1 or 2 revolutions when you turn off the motor when at normal operating temp. PG.

KB9GKC

[QUOTE=trsulliv;1569659473]Can somebody tell me how to determine when a fan clutch needs to be replaced? It is on a SB engine and is the orginal clutch. It does not turn very freely when the engine is off, maybe 1/2 revolution.

Also, what happens when it doesn't work?

Three things can happen:
1). Seizes up and runs at full speed of engine all the time (robs horsepower) Should spin easily when cold, give it a spin with engine off.
2). Bearing gets bad, check with engine off, grab fan and push toward the radiator and pull back toward the engine, the fan bearing should have no play in it.
3). Start engine and run with engine bay open and wait for car to reach operating temperature. You should be able to hear fan clutch engage (you will hear it blow harder when it engages). If your car begins to overheat and you never hear fan engage you might have a bad thermostat spring.

Hope this helps,
Douglas in Green Bay

trsulliv

Thanks for the help. I am running it at Road America next weekend and at WOT, it does generate a lot of heat.

Any ideas on who has high quality new units?

0Willcox Corvette

trsulliv-

You might also check for oil around the main shaft of the clutch fan. Usually if you are seeing oil, the fan will not pass the suggested test Douglas gave you.

I think four seasons has a direct service replacement for your car under part number 2714. You should be able to pick this up at most parts stores. I'm not positive this is the correct number so take your old one with you and make sure both bolt patterns are the same as well as the center hole in the hub for the water pump. The current delco replacement part number (twice as high) is 88961763.

Willcox

CheezMoe

I bought a NAPA replacement and it's good. Overall NAPA still carries many drivetrain and chassis parts for our cars at very reasonable prices.

Mike Ward

Sounds like yours is working properly. If it didn't work, the engine would tend to over heat (really overheat, not the silly 210 some people worry about)

Don't replace it wit a spacer, use the proper clutch.

trsulliv

Thanks. took it for a drive to warm it up, and then shut it down. The blades spun, Iwould guess 4-5-6 revolutions before it stopped. As soon as the motor was shut off, there was some resistance when I turned it by hand, but not a lot - it was not free spinning, but it wasn't real hard to turn either. Sounds like I need a new - right?

trsulliv

Thanks. I took it for a drive to warm it up, and then shut it down. The blades spun, Iwould guess 4-5-6 revolutions before it stopped. As soon as the motor was shut off, there was some resistance when I turned it by hand, but not a lot - it was not free spinning, but it wasn't real hard to turn either. Sounds like I need a new - right?

CheezMoe

Based on what your saying I agree with Mike Ward that it would appear to be working properly. As KB9GKC stated, when they go go bad the bearing's lock up and they get stiffer have play in and out. You can also hear them progressively howl as the bearing's get more and more seized up.

What symptoms are you chasing? is your car overheating regularly?

Peterbuilt

4 or more revolutions when hot is to many, I have a 1990 article from Corvette World that shows how to adjust the clutch fan for less slip, PM me your email and I'll send it to you. PG.

trsulliv

On the street I have no overheating problems, but running at Road America the temps really get up there, although I have been able to keep them at about 210 with the heater going to. The engine is a ZZ3 with Hooker headers and a Q jet. I am running it through a 5 speed, but have an orginal Automatic radiator. The rad has been cleaned out.

Mike Ward

210 is a perfectly acceptable temperature. That's what they ran at when brand new under those circumstances.