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Fan clutch adjustment - again

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  • Timothy B.
    Very Frequent User
    • January 1, 2004
    • 438

    Fan clutch adjustment - again

    I have been reading the posts on this, and still have a question: My fan clutch on my 67 327/300hp car is the Eaton replacement style unit with the coil spring. The clutch was purchased in the mid 80's but has probably only seen 1000 miles since then. From what I understand, my unit is probably designed to engage at too hot a temp for my car (like maybe 210 deg. F). The clutch doesn't appear to be engaging by using the spin count techniques mentioned in earlier posts. It doesn't appear to be acting any different now than when it was new, just probably the wrong engagement temp? Does this sound right?

    Next question is this: Should I try the simple adjustment as mentioned in various articles? They describe moving the tang around to the opposite side, but that obviously completely overrides the thermostat funcion. I suspect the tang only needs to be moved a few degrees. I tried heating the spring up with a blow dryer and it only moves maybe 20 degs no matter how hot I try to get it. Clearly 180 degrees is overkill.

    Any advice?
  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43203

    #2
    Re: Fan clutch adjustment - again

    Tim-----

    20 degrees of movement is about the maximum that the coil is designed to move. I expect that the most likley result of messing around with the clutch "adjustment" is going to be the need to replace the clutch. I'd leave it alone. I believe that this Eaton fan clutch has been recently GM-discontinued so getting a replacement if you ruin the one you have might not be so easy.
    In Appreciation of John Hinckley

    Comment

    • Timothy B.
      Very Frequent User
      • January 1, 2004
      • 438

      #3
      Re: Fan clutch adjustment - again

      Thanks Joe. I don't think it is an option to leave it alone since it isn't engaging and cooling properly when the engine is hot. The spring easily pops out of the retainer and can be rotated, so I think I will try tonight doing so and seeing if the friction increases appropriately. If it does, I can either leave it that way (as the earlier articles suggest) or try relocating the tang such that it is low friction when cool and high friction when at operating temp.

      I guess I could send it off to the folks (LUna???) who rebuild original clutches and request that he recal it to the correct temp? That may be costly for what is a non-original clutch.

      By the way, this clutch appears to look the same as original clutches, so did GM originally use this same Eaton clutch on my car? Even the stamped lettering on mine is the same as those photos I have seen on ebay and elsewhere of clutches that are claimed to be original.

      Comment

      • Joe C.
        Expired
        • August 31, 1999
        • 4598

        #4
        Re: Fan clutch adjustment - again

        Tim:

        The replacement Eaton unit is very close to the original. The main difference is in the shape of the oil reservior, which is the raised area on the surface of the hub.

        Here is a link for Fred Oliva, who rebuilds the clutches. If you are extremely concerned about originality, then Fred usually has original "cores" that he can rebuild for you, at extra cost.



        What makes you so sure that your clutch is N.G.? They are very hard to diagnose as inoperative. Really, IMHO, the only way to tell, is if the bearing is shot, and/or if there is evidence of mineral oil leakage.

        Case in point: At one time, I believed my clutch to be inoperative. So I borrowed a friend's newly rebuilt original. Brand new, still in the box. IT MADE NO DIFFERENCE at all. I reinstalled my old one, and it remains still......the problem was elsewhere.

        Joe

        Comment

        • Timothy B.
          Very Frequent User
          • January 1, 2004
          • 438

          #5
          Re: Fan clutch adjustment - again

          I don't think my clutch is bad - only calibrated to a higher setpoint. In reading various posts (including some from Fred Oliva), they mention testing the functionality of the clutch by comparing the number of rotations of the fan as the engine is shut down with and without the engine being at operating temp. On my car, there is no difference. I understand from those posts that there should be a difference. Also, now that the weather here in Houston is hot I have noticed that driving on a hot day the temp Gage reads just above the first tick mark. When I pull to a light or traffic and have to sit for awhile with the car not moving, the temp rises noticeably. I have read that this is another indicator of the fan clutch not engaging proper. I am not having an overheating problem (I have a new Dewitt's rad in place, new thermostat, and new water pump), but I do notice the difference with and without the car moving. As I have researched this topic in old posts and in NCRS article archives, they mention replacement clutches having a 210 deg setpoint while the originals had a 195 deg setpoint 1967 and before. My clutch is a 1984 Eaton replacement and likely has the higher setpoint.

          See attached link to an earlier string...




          Comment

          • Joe C.
            Expired
            • August 31, 1999
            • 4598

            #6
            Re: Fan clutch adjustment - again

            Tim:

            Suit yourself. You cannot reengineer the unit, nor is it wise to attempt to chance the "setpoint". There is no "setpoint" per se. The viscous fluid gradually increases friction as the spring heats up and expands, which varies the size of an internal orifice. It sounds like you have made up your mind, so, when you experiment, be sure to rotate the spring in VERY SMALL increments. I don't know how you will do that, as there is no provision for adjustment. As I said before, it is VERY DIFFICULT to diagnose a weak clutch, and the so called "spin test" is pure nonsense. That test is only valid if the unit is completely dead. If you are not sure, then I recommend swapping in a known good unit to compare. I have a feeling that you will see no difference.
            It is normal to see a slight temp rise at idle. These old cooling systems were designed to operate on the ragged edge.........there is almost NO excess capacity built in. Combine this with the inaccuracy and extreme sensitivity of the temp gauge/sender systems, and you have lots of folks running off half cocked about "overheating". If you do, indeed have a problem, it could be timing, heat riser, mixture, or a host of other things.

            Good luck,
            Joe

            Comment

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