visous fan
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From: Port Coquitlam, BC Canada
visous fan
Well after reading some here about the clutch fans, I tried spinning mine when the truck was warm, my fan only moved about a 1/4 turn when I tried spinning it.
So I gather my fan may be alright, will wait till it cools here at work and try it cold.
So I gather my fan may be alright, will wait till it cools here at work and try it cold.
Fleet Mechanic
Joined: Feb 2006
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From: Lorain County, Ohio
Originally Posted by partsman01
Well after reading some here about the clutch fans, I tried spinning mine when the truck was warm, my fan only moved about a 1/4 turn when I tried spinning it.
So I gather my fan may be alright, will wait till it cools here at work and try it cold.
So I gather my fan may be alright, will wait till it cools here at work and try it cold.
What year is your truck? If it's about 8 years old or more (or more than ~75K miles) just replace the clutch. They're a maintenence item that is most often overlooked until it fails completely.
One of the first signs of a weak fan clutch is reduced AC cooling at idle and low speeds.
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From: Hesperia, CA
The procedure we used, back when I was doing it, to test the fan clutch was to use cardboard to block the radiator. The cardboard had a hole cut in the center of it the same size as the hub unit on the clutch. This was about six inches. We removed the radiator cap and put a candy thermometer in it to measure the temperature. You place the cardboard in front of the radiator with the hole centered over the fan hub. We would run the engine until the fan clutch kicked in. You use the candy thermometer to see where the fan clutch kicked in at.
The hole provided the heat directly to the fan clutch giving a more accurate reading of when the clutch kicks in.
The hole provided the heat directly to the fan clutch giving a more accurate reading of when the clutch kicks in.
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From: Port Coquitlam, BC Canada
It is a 1977 F-250 400/6.6litre C6 auto.
Some of the topics to do with cooling made me curious if I could tell if it works.
I think up here the clutch goes for 71.00 CDN for mine, which I believe is a 2797 from Haynes.
Some of the topics to do with cooling made me curious if I could tell if it works.
I think up here the clutch goes for 71.00 CDN for mine, which I believe is a 2797 from Haynes.
Fleet Mechanic
Joined: Mar 2004
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From: Hesperia, CA
Originally Posted by partsman01
It is a 1977 F-250 400/6.6litre C6 auto.
Some of the topics to do with cooling made me curious if I could tell if it works.
I think up here the clutch goes for 71.00 CDN for mine, which I believe is a 2797 from Haynes.
Some of the topics to do with cooling made me curious if I could tell if it works.
I think up here the clutch goes for 71.00 CDN for mine, which I believe is a 2797 from Haynes.
Also unless you are doing a lot of heavy duty stuff with that truck I would just get the regular duty clutch instead of the heavy duty. They seem to be more reliable. (and cheaper)
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From: Hesperia, CA
The only way you are really going to test it properly is with the cardboard as I described above. You will hear the roar when the thing locks up. If you get that engine over 220 and that fan is not roaring then the clutch is no good.
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From: Lorain County, Ohio
Originally Posted by wb6vvv
The only way you are really going to test it properly is with the cardboard as I described above. You will hear the roar when the thing locks up. If you get that engine over 220 and that fan is not roaring then the clutch is no good.
In all fairness, that IS a good test if you have an engine that's running too warm at low speeds, especially on a vehicle that doesn't have AC.
The engine cooling system is very forgiving of a weak fan clutch. On a truck with no AC and a weak fan clutch, you won't notice it until the clutch is almost dead at idle. On a vehicle with AC, the first indication of a failing fan clutch is poor AC cooling at idle or low speed.
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From: Hesperia, CA
Originally Posted by lsrx101
That's actually not a good test either. It tells you nothing about how much RPM differential there is at idle when it's really needed for AC operation. That test only tells you if it is actually capale of "locking up" under full heat load.
In all fairness, that IS a good test if you have an engine that's running too warm at low speeds, especially on a vehicle that doesn't have AC.
The engine cooling system is very forgiving of a weak fan clutch. On a truck with no AC and a weak fan clutch, you won't notice it until the clutch is almost dead at idle. On a vehicle with AC, the first indication of a failing fan clutch is poor AC cooling at idle or low speed.
In all fairness, that IS a good test if you have an engine that's running too warm at low speeds, especially on a vehicle that doesn't have AC.
The engine cooling system is very forgiving of a weak fan clutch. On a truck with no AC and a weak fan clutch, you won't notice it until the clutch is almost dead at idle. On a vehicle with AC, the first indication of a failing fan clutch is poor AC cooling at idle or low speed.
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That's the reason that you can't get good Ford service at a dealer (Or any dealer for that matter). Independents know how to do these things because they've actually learned it rather than read it. LSRX is right about the clutch check as I know from personal experience. The test is a good one but it's not 100%.
I work in an electronic shop and what I've done is put reflective tape on one blade and checked the RPM with a reflected light tachometer. Compare that to the engine RPM and you can get a real good check, but most people don't have access to that type of tach.
I work in an electronic shop and what I've done is put reflective tape on one blade and checked the RPM with a reflected light tachometer. Compare that to the engine RPM and you can get a real good check, but most people don't have access to that type of tach.
Last edited by 2000Ford2000; Jul 14, 2007 at 07:00 AM.
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From: Lorain County, Ohio
Originally Posted by 2000Ford2000
Content trimmed
I work in an electronic shop and what I've done is put reflective tape on one blade and checked the RPM with a reflected light tachometer. Compare that to the engine RPM and you can get a real good check, but most people don't have access to that type of tach.
I work in an electronic shop and what I've done is put reflective tape on one blade and checked the RPM with a reflected light tachometer. Compare that to the engine RPM and you can get a real good check, but most people don't have access to that type of tach.
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From: Hesperia, CA
Originally Posted by lsrx101
That method actually works pretty well. It will tell you the fan speed at all RPM and the airflow can be judged from that pretty accurately. Like you said, though, most folks don't have a strobe tach. Being a wear item, I find it easier to replace a suspect clutch.
Last edited by fasthauler; Jul 14, 2007 at 12:16 PM. Reason: error
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From: Lorain County, Ohio
Originally Posted by wb6vvv
It would be a heck of a lot cheaper to just replace it as well, but what happens if the new unit is bad also? (This does happen) At least testing it with the cardboard does give you and idea if it is functional at all. Most of the guys on here are diyer's and do not have access to sophisted equipment. It would be cheaper for them to take it to a garage and have it done than buy that kind of equipemnt, but they wouldn't be here looking for advice if they were willing to do that. The section I posted was only part of the test procedure in the Ford manual. It is two pages. I just paraphrased what I thought was the most expedient thing to do.
As far as a new clutch being bad out of the box, yes it can happen. It casn happen with any part. That's why it's important to use quality parts with a good track record of quality control. The likelihood of an NIB failure will be statistically less.
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Being from a shop that has delt with this problem, what i do is just replace a suspected weak clutch. if a little water on the condenser drops head pressure like a rock, more than 60 pounds or so, replace the damn clutch. my shop rate is $100 per hour for refridgeration diagnostics. Clutch is approx $80 and $50 to r&r. seems like a no brainer to me.
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