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Fan Fluid Coupling

Discussion in '80-Series Tech' started by MTNRAT, Aug 10, 2003.

  1. MTNRAT

    MTNRAT

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    I seem to be running a little hot on big hills. I think it may be the fan fluid coupling. I ran the cruiser till it was hot, stopped, turned off the engine, opened the hood and hand rotated the fan. It spun with very little resistance. I thought when it was hot the fan should not spin easily. If I am correct I need a new fluid coupling. Can anybody confirm my diagnosis??
    Thanks,
    Sean
     
  2. PHAEDRUS

    PHAEDRUS

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    when you run at operating temp the fan should be able to be moved by you r hand but with some good force behind it, it should not spin easily or you are right on the money with fan clutch. I just changed mine out a few months ago(92 3fe yeah stfu junk i love my 3fe 8)) its a pain in the ass unless you want to remove the radiator. I just pulled the battery tray and fan shroud out of the way and tore into it. I pulled the blade first then backed off the clutch. new oem clutch form local stealer was $93 if i remember correctly. Not too bad over all with a good set of box end wrenches.
    there is my two cents im sure others will chime in
    Dave
     
  3. Beowulf

    Beowulf

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    Sean,

    Many people are having cooling problems again this summer season. Diagnosing the root problem has become an educated guess for all of us. The bottom line is that the cooling system in a stock FZJ80 is more than adaquate to handle a heavily optioned and heavily loaded 80 in 100 degree heat at high altitude, climing steep hills for hours on end. If one piece isn't working well, then problems occur and it can happen quickly.

    In your case it sounds like the fan clutch could be the problem. Before you replace it try to determine if the other pieces are working properly.

    * Is the thermostat opening?
    * Is the radiator cap holding the correct pressure? (Added 14.Aug)
    * Is the coolant in good shape? (50/50 with distilled water, good quality, proper level)
    * Belts in good condition and tight?
    * Can you detect any crud in the radiator? Look carefully at the cap, in the top, and
    maybe pull the lower hose.
    * Check for crud in the radiator fins. Mud, bugs, dirt. Photoman had some pics of his 97 stock radiator
    after it was pulled. Quite a mess as I recall.
    * Review the threads on head gasket and other cooling issues. Does anything sound
    likely?

    Keep us posted and good luck!
    -B-
     
  4. landandsea

    landandsea

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    I'll bet everyone is just waiting for me to suggest the towel around the hand test, but noooo way.

    However, a good way to test for a radiator problem is to bring the engine to operating temp, (and don't skip this step) shut the engine down, then feel the radiator for cold spots. A cold spot naturally indicates that coolant isn't flowing there.

    I was quite confident that my radiator was in great shape simply because I paid the dealer to flush and service it. But when I had temp problems, I found cold spots on the radiator. Replaced the fan clutch and radiator and now I can't get the temp to rise even purposely trying to.

    Good luck

    Ed
     
  5. IdahoDoug

    IdahoDoug

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    I agree with Beowolf that these beasts are fine on cooling capacity. We routinely tow 6000lbs of boat over mountain passes on hot summer days. Many are so steep I have the tranny in 1, with my boot 3/4 deep in the throttle for several minutes and I've never seen the needle move more than one needle's width - that was on a 98 degree day w/ 6 people, luggage, roof box, the boat, and before I changed the plugs and cap (which it needed).

    I've owned the truck since '93 and have religiously changed the coolant every other year. Used Prestone green, though it's been maligned on this list, and now it's full of Dex orange. One thing I've done a couple times that others don't seem to is a thrice repeated thorough flush that includes removing the block drain. It's a pain to do because you're fully under the truck to pull it and inevitably get splashed in the process, but you would not believe what comes out of there. I also recently sprayed the radiator fins front and back with concentrated Simple Green, let it soak and sprayed them clean for maximal air/metal heat transfer. Did this on the Subaru wagon at the same time in search of the source of weak A/C output and the vent temp dropped from an unenthusiastic 62 degrees to blowing ice cubes at 47 degrees.

    So, a little care and these things will do fine on cooling. I doubt many here have done as much hard work with their 80 as we have in 10 years, but I bet many have neglected one or another key cooling component enough that their system is maxed just driving around on a hot day with the A/C at full blast.

    (jumping off the milk crate)..
     
  6. MTNRAT

    MTNRAT

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    Thanks guys. I will go through everything and tell you what I find.
    Sean
     
  7. Beowulf

    Beowulf

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    Sean,
    Added one thing to the list:

    * Is the radiator cap holding the correct pressure?

    -B-
     
  8. landandsea

    landandsea

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    -B-, I think the pressure just raises the boiling point. I don't believe it affects the operating temp level.

    I'm willing to stand corrected if proven wrong.

    Ed
     
  9. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    Ed,

    That's true. However, if the cooling system will not hold the specified pressure there is a problem. For example a failing head gasket or leaking radiator or cap. Or perhaps a cracked head.
     
  10. Beowulf

    Beowulf

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    Ed,
    When the boiling point is lowered you will eventually boil enough of your coolant that the volume will be too low and overheating will occur.
    -B-
     
  11. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    Or if yer boat is toooo big :eek: And yer trying to out-run a Wulf ::)
     
  12. Scamper

    Scamper

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    Actually, the increased pressure results in higher boiling point of the fluid which in turn prevents boilover (or at least reduces it somewhat). The value of the higher boiling point is that, amoung other things (like coolant loss), it creates a greater temperature gradient between the outside air and coolant which translates to better cooling efficiency thru the radiator. Even if you were not to loose all your coolant via evaporation (i.e. boil over) due to no cap (or bad cap), you'd suffer less efficient cooling. The higher temperature also means that you can operate a water-based coolant system at temperatures approaching the boiling point of water--that's the primary basis for it.
    Tom
     
  13. landandsea

    landandsea

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    All valid points, for sure.

    My comment concerned analyzing mystery reasons for high operating temps. Like when everything SEEMS to be operating properly. A radiator cap not holding pressure will leave a trail of clues (or should I say a stream of clues).

    Likewise, a loss of coolant into the engine. The clue - loss of coolant.

    Ed
     
  14. MTNRAT

    MTNRAT

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    Well, I got a new fluid coupling. Comparing the feel of the old one to the new one is night and day. The old one has spots where there is no resistance to spinning and the new one has a constant resistance. I think that was the problem as there was absolutely no sludge to be found in the hoses or the old rad. Being the " how can I overdo it" kind of person, and pissed :mad: at running too warm especially when towing, I ordered and put in one of the 3 core brass radiators and a new thermostat. So I guess i basically have a new cooling system :D. Now to see what happens when I pull my boat 800 miles next week.
    Sean
     
  15. landandsea

    landandsea

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    Sean, did you feel the radiator for cold spots? the rad can be partially plugged without apparent sludge.

    I'll bet there are guys wearing S/C's and "old" cooling systems just waiting for your feedback.

    Ed
     
  16. MTNRAT

    MTNRAT

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    I did feel for cold spots, but did not find any. That does not mean that they are not there though. With the fan that comes with the S/C it is difficult to get behind it and feel much of the rad. Now that it is out maybe I will get it tested "for the cause". Still have to pull the boat up a pass or two to see if my problem is gone. Will be back after the Labour day weekend with that answer.
    Sean
     
  17. IdahoDoug

    IdahoDoug

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    Can someone definitively explain how much cold vs hot fan resistance should be in the fluid fan coupling? When hot, I can use my fingers as though I'm starting a model airplane and my best effort gets the fan to rotate a quarter turn after I let go. This is pushing it as hard/fast as I can. When it is cold, I don't notice as much difference as I'd expect, so...

    IdahoDoug
     
  18. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    Doug,

    Silicone filled fan clutches have puzzled the heck out of me for years. They remind me very much of trying to adjust hood hinges. IE when you move them they do the opposite of what you expect. A cold clutch is stiff, a warm one is loose, a hot one is????? I have shut a HOT motor down and been able to spin the fan much more easily by hand than the same engine cold. I don't get it. It may have something to do with rotational forces and that bi-metalic coil spring thingy in the center front of the clutch. Where is an automotive engineer when you need one?

    Dan.
     
  19. MTNRAT

    MTNRAT

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    Yea the fan fluid coupling is confusing. The only thing definitive that I can say is the old one and the new one acted and felt different. What that difference means I have no idea.
    Sean
     
  20. landtank

    landtank SILVER Star

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    The Viscous coupler turns harder when cold because the fluid is thicker. When hot the fluid is thinner allowing it to turn easier. When running the Bi-metal valve reacts to the air temp passing through the radiator and restricts the flow more as the air temp rises and transmits more drive to the fan. Or at least that was what was taught in school ;).