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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Joe-NC on July 15, 2015, 05:07:23 pm
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My fan clutch just came apart yesterday and destroyed a perfectly good radiator that was only a year old. I still haven't figured out exactly what happened, but there's a big hole in the bottom shroud where I think a board may have gone through it as I was driving down the road at 60 mph.
1) I took everything apart and bent the fan blades back so they look pretty good, but I decided it would probably be too out-of-balance to use it again. What's your opinion?
2) My fan had 7 blades, but I went to a junkyard and got a 5 blade one for $45. Why are these OEM blades not evenly spaced? Is there a certain way they have to be installed so they are counterbalanced with the engine or something?
I didn't realize how hard it was to find standard aftermarket belt-driven blades in stock even though I live in an area with lots of suppliers. I can't convert to an electric system right now due to time and money.
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My fan clutch just came apart yesterday and destroyed a perfectly good radiator that was only a year old. I still haven't figured out exactly what happened, but there's a big hole in the bottom shroud where I think a board may have gone through it as I was driving down the road at 60 mph.
1) I took everything apart and bent the fan blades back so they look pretty good, but I decided it would probably be too out-of-balance to use it again. What's your opinion?
2) My fan had 7 blades, but I went to a junkyard and got a 5 blade one for $45. Why are these OEM blades not evenly spaced? Is there a certain way they have to be installed so they are counterbalanced with the engine or something?
I didn't realize how hard it was to find standard aftermarket belt-driven blades in stock even though I live in an area with lots of suppliers. I can't convert to an electric system right now due to time and money.
- Replace or patch that damaged fan shroud, so that it doesn't breakup further and get sucked into your replacement fan blade or window your replacement radiator, and to ensure that all of the cooling air is drawn through the radiator core instead of around it.
- Buy a high quality thermal fan clutch to replace the one that was guillotined.
- NEVER STRAIGHTEN A DISTORTED FAN BLADE!! Metal fatigue from straightening bent blades too frequently results in blade disintegration. Pray that you are never working on a motor with the hood up when a blade comes apart. I've seen fan blades explode and cut their way right through steel hoods. I've also seen respectably sized ice-cream scoop gouges in the street from blade disintegration. It's amazing the damage that fan shrapnel can cause!
If a blade is bent, replace it!
- OEM fan blades on our trucks are asymmetric (unevenly spaced) for a couple of reasons.
- They create less noise by breaking up standing waves that develop between the radiator and the blade.
- They are less prone to cavitation, which results in slightly improved air flow over a broadened RPM range.
Asymmetric blades are balanced from the manufacturer and can be installed with no regard to "clocking." But, there is a leading side that must face the radiator. Most aftermarket fan blades have symmetric blade spacing and work suitably well at the expense of slightly increased noise.
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Wow. Thanks so much for the thorough reply. That's exactly what I was hoping for.
Just got done cleaning and painting the new fan blade. The old one will go into the scrap pile. Yep, I was planning to repair the shroud with a rivet gun and whatever material I can find. (vinyl siding, vinyl flashing, etc) The junkyard wanted $75 for the whole shroud, but I think I'll just keep the one I have for now. I'll wait til I drop a new engine in it and completely restore everything under the hood at once.