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3406B Running hot?

Discussion in 'Trucks' started by Keith Merrell, May 14, 2022.

  1. Keith Merrell

    Keith Merrell Well-Known Member

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    I have a 1986 Freightliner 10 wheel dump truck with a Cat 3406B and 13 speed transmission. I pulled my 20 ton tag trailer up a 6% grade today empty, and it was about 90 degrees outside. I was in 8 low doing 900 on the pyro. Towards the top of the hill, I noticed my water temperature was at 208 or so. (It normally runs about 185-190 when idling or on flat ground) so I backed it down some to keep the temperature from rising any more. I do not have an air fan hub on this truck, just a thermal one. First off, is this normal, second what should I look at first? Thanks in advance, this is my first real truck and I don't know much about them.
    Keith
     
  2. Truck Shop

    Truck Shop Senior Member

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    When was the last time the core was pressure washed? If it has A/C and Air Charge cooler over time
    the core will clog with fine dust. Grain trucks I use to work on would need cleaned twice a year
    sometimes. That viscus fan may not be pulling enough air also.
     
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  3. mekanik

    mekanik Senior Member

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    A viscous fan hub has a life expectancy. The very small amount of fluid eventually disappears
    and the engine starts to run hotter.
     
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  4. skyking1

    skyking1 Senior Member

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    if that fan is working properly you should be able to hear a change when it gets that hot.
     
  5. Keith Merrell

    Keith Merrell Well-Known Member

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    Thanks, sounds like it is the fan clutch then, because I hear no change and the temp seems to just keep climbing with no stopping it even if you drop gears.
     
  6. Keith Merrell

    Keith Merrell Well-Known Member

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    I made sure the outside of the radiator was clean, is that what you mean? I don't know any of the history on the truck.
     
  7. Delmer

    Delmer Senior Member

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    NO, the outside can look clean, you can't see the whole outside if there's other coolers in the way, and then you'd have to shine a light from the other side and look through to see how dirty the fins are. One way to check, is to rinse with a garden hose, then spray on some detergent, keep rinsing and repeating. It will run clean for a bit, then you'll hit a dirty spot, and you know it's dirty.

    Sounds like the clutch though, if it stays cool enough when moving, but overheats going up a grade.
     
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  8. skyking1

    skyking1 Senior Member

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    ^good stuff Delmer. I ran a 977 raking up roots on a golf course job, very dusty and they blew that out every week or it would climb on up there. I too think it is the fan but a clean rad and CAC would not hurt.
     
  9. suladas

    suladas Senior Member

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    That seems like a high temp for it sitting. Unless my gauge is off mine sits at 170 idling and normal driving if it's not working too hard. I do find on the warmer days like above 85 if it's really working the fan can't keep it cool if pulling up a grade with my 210 on but I am at about 90,000lbs and have to take it easy, seen as high as about 205. I just chalked it up to being older and cooling system not as good as newer stuff, below about 85 it will keep it cool no problem.
     
  10. Truck Shop

    Truck Shop Senior Member

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    To properly clean a radiator core externally, A/C denser and air charge cooler has to be removed. And
    carefully using a pressure washer {not to close} start at front side and doing your best from back side.
    Air charge cooler can be washed as well as A/C denser.

    Normally on a viscus fan hub if it's leaking fluid-dust/oil will collect on the front side, check with mirror.
     
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  11. Keith Merrell

    Keith Merrell Well-Known Member

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    Thanks, I will make for sure the rad and CAC is clean. Sounds like I need a fan clutch though.
     
  12. Mark250

    Mark250 Senior Member

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    Hi after you have checked all of the above.check to see if the water pump impeller is not turning on the shaft.the impeller is a taper fit on the shaft and if not fitted correctly can come loose.
    Also there were a batch of water pumps that had a plastic type impeller bonded to a steel hub, when hot the impeller would spin on the hub
    Mark
     
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  13. Keith Merrell

    Keith Merrell Well-Known Member

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    Thanks. I cleaned the radiator tonight with my friends home made radiator gun. Will also test fan clutch and inspect water pump.
     
  14. Keith Merrell

    Keith Merrell Well-Known Member

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    Removed fan clutch. Should I replace with a Horton air fan clutch? Also I am assuming this flange is part of the clutch itself as there are no fasteners holding it on.
     

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  15. Truck Shop

    Truck Shop Senior Member

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    The Horton is a complete unit. You will need a fan solenoid, temp sender, cab switch for manual over ride.
    Kind of spendy because you will get hit for no core unless you buy new. Personally I would find a
    replacement viscus fan hub and leave it be.
     
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  16. Keith Merrell

    Keith Merrell Well-Known Member

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    Could I set up the Horton just to be on / off manually? With no sending unit, just the new clutch hub and a cab switch and small solenoid and an air line? And make sure the right nut is behind the wheel?
     
  17. Truck Shop

    Truck Shop Senior Member

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    You could yes but does this rig have working A/C? I have known a few that have done that and wished
    they had not later on. Only takes one time on a hot day.
     
  18. Keith Merrell

    Keith Merrell Well-Known Member

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    No AC doesn't work
     
  19. Truck Shop

    Truck Shop Senior Member

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    Well no problem there with a A/C pressure switch. I can't tell you what to do but if it was me I would
    wire it up for automatic and manual over ride.
     
  20. Keith Merrell

    Keith Merrell Well-Known Member

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    Interested in the Horton because I am having a tough time finding the thermal clutch which is what I want to do, no part number...