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Fan clutch woes...too much suck?

cheavyk10

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Doing some routine maintenance on my 93 S10 Blazer, getting it ready for a Christmas road trip. I'm about to do 3,000 miles in a 28 year old vehicle. Who will be the first to call me crazy?

Anyway I noticed a bearing scraping sound at idle which had me really paranoid which I determined was the fan clutch making noise. Grabbing the fan with the engine off there's a lot of play. So no worries I ordered up a fan clutch. I noticed all the parts stores and RockAuto and Amazon all had a fan clutch with the same part number. So I chose the cheapest deal on a severe duty fan clutch.

Installation was a breeze but now it seems like the fan clutch is engaged all the time even at idle. It is moving a ton of air at idle and all speeds above, it sounds like a hurricane under the hood.

From what I understand the fan clutch is only supposed to kick on at certain temperatures. Is it possible I have a defective fan clutch right out of the box? You can freely spin the fan with the engine off so it's not completely locked up.

Or was the old fan clutch not working at all so I never heard it moving air? Never had any overheating issues with this truck.

Any thoughts or experiences would be truly appreciated I might even put the old clutch back on at this point.
 
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6872xtc

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I believe that it is possible for the manufacturer to set the clutch up too tightly from initial. I used to have '95 S blazer and I typically didn't hear the fan at all. I had to leave it idling with the A/C on for quite a few minutes, or something like that to be able to hear the fan after raising the rpm. It was white, and I believe that helped some. I have always heard the fan run more often with darker exterior colors.
I know that @mrk5 found a way to adjust the fan clutch some, but they might not all be adjustable.
 

dyeager535

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At one point some of the cheap replacement clutches were not temp controlled...those were always easy to tell because they are missing the thermostatic coil on the front of the clutch housing.

Not sure about that vintage looking the same as earlier, but do the two clutches look essentially identical?

If you Google thermostatic fan clutch you'll find pictures of both styles.
 

cheavyk10

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Yes they look identical, I noted there is a light-duty version that was thinner with less fins. And both have the coil on the front of the housing.
 

dyeager535

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I'd say it's bad then. Typical operation of the clutches I'm used to is that on startup they lock up, but after a few seconds of running you can hear (and feel, if hood is open) that the clutch disengages.
 

cheavyk10

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Yeah this thing is on constantly. I might try another one from the local auto parts store. Funny thing is I got it off Amazon for $42, and my local O'Reilly has one with the same part # but a different brand name for $70. So much for saving money.
 

Fastereddie

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Yeah this thing is on constantly. I might try another one from the local auto parts store. Funny thing is I got it off Amazon for $42, and my local O'Reilly has one with the same part # but a different brand name for $70. So much for saving money.
Amazon is full of reject, Misboxed, Chinese knockoff crap. You have to be very careful and or lucky to get what you actually want nowadays.
 

Wes Harden

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you got the severe duty it will run locked up more than the normal duty, and there are both units made for each application, thermostatic and non-thermostatic.

I am not saying the one you have isn't bad, but if it free spins with engine off and has resistance warm it sounds like it's working to me.
 

mrk5

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I used a piece of saw blade to change the slot where the end of the thermostatic coil is held. Seemed like a very small difference in that slot meant a pretty significant change in temperature range. I'm talking about 1/16th of an inch or less.

2020-09-22 14.23.47.jpg

If you felt like taking the time, you could try messing with the slot on yours to see if you can tune it.

I've also noticed when swapping to extreme duty fan clutches you will hear them more. According to an article I read, the different duty ratings actually lock the clutch up at different engagements.
  • Standard: 60% to 70% lock up
  • Heavy Duty: 70% to 80% lock up
  • Severe: 80% to 90% lock up
I'm assuming you've driven it around for some time, but just in case I will mention the clutch will be engaged for the engine start up and then disengage after running for a little while. I notice the fan clutch on our 2500HD runs longer than other vehicles I've driven, but it does disengage after about 4 to 6 blocks of driving. This is how I figured out my son's truck had a failing fan clutch. He had been having some intermittent overheating that was looking like a thermostat getting stuck closed. One morning he called me and said there was a roaring sound from the engine bay. I was surprised and asked if that was the first time he'd ever heard it. It only happened once which told me the fan clutch wasn't engaging. When I used to daily his pickup, it would always roar the fan clutch at the first startup. When we changed the fan clutch it was covered in dust and blew dirt everywhere when we first started it. Apparently that fan clutch hadn't been engaging properly for a while to the point it was gathering dust. The problem with teen drivers, they don't keep the best watch on the gauges.
 

cheavyk10

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@mrk5 Thank you , this is some good info. The blazer has the heavy duty cooling package, which was standard with the CPI 4.3, so I figured the Severe clutch was the right one, based on some images I compared online. I'm thinking the old clutch must of been of a lesser variety, hence the extreme difference I noticed.
 

cheavyk10

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UPDATE: I ended up ordering the genuine GM part, which for this rig was listed as heavy duty. Installed it and it works great, and is way quieter than the severe duty version. The severe duty never even disengaged at highway speeds. Also, the temp gauge went up and down way too much, depending on vehicle speed. I should be all set for my road trip now. IMG_20211217_130519735.jpg IMG_20211217_130605137.jpg
GM on the right, Hayden on the left, very similar looking. Both clutches are made in Mexico.
IMG_20211217_141939194.jpg
 
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