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How do I know the fan is working properly??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by smack, Jan 19, 2003.

  1. smack

    smack 1/2 ton status

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    Stupid question, maybe, but I can't get my engine to warm up beyond 110 degrees. Happening since I put in a 160 thermostat.
    How can I tell if the fan is not permanently engaged??
    Duh,
    smack
     
  2. 90K5

    90K5 1/2 ton status

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    Are you going by the stock gauge? it is probably wrong, might need a new sender
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Trust me, you'll know if the fan clutch is stuck on.

    Take your truck out on the highway and get her up to about 65MPH in D. Does your truck sound like a 747 powering up for takeoff? If so, it's time to replace the fan clutch.
     
  4. Blue85

    Blue85 Troll Premium Member

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    When the engine is warmed up, turn it off and see if you can turn the fan by hand.
     
  5. Sandman

    Sandman 3/4 ton status Author

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    Sounds like the thermostat might be sticky,
     
  6. HarryH3

    HarryH3 1 ton status Author

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    Driving 60 mph down the highway moves a lot more air through the radiator than the fan does, so you don't need to worry about a fan "overcooling" an engine. The thermostat holds coolant in the engine until the coolant temp reaches the opening temp of the thermostat. So either the thermostat is bad or it was installed crooked. If it is setting slightly off to one side, then the coolant can leak past it and keep the engine too cool.
     
  7. wrathORC

    wrathORC 1/2 ton status

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    I have the exact opposite problem. Mine overheats... when it's 8° outside.

    If the fan is stuck on it'll always "roar". In other words, when you open the hood you won't be able to set a paper towel on the air cleaner without it trying to make like a paper airplane.

    First, start it up when the truck is cold and look down the radiator with the cap removed. You should notice miniscule amounts of waterflow. When the thermostat opens you'll know it. If there is a lot of water flowing it means your thermostat is stuck open. For the most part, running a 160° thermostat is like running without one.

    You also might want to check it with a mechanical gauge in case it's just the sender. The sender for the gauge is the one by cylinder #1 if I remember correctly.
     
  8. smack

    smack 1/2 ton status

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    Thanks, all for the replys.
    I'm not apt to suspect it's the temp sender since it started immediately after installation, but just in case, where is it?. The unit on the driver's side block is the knock, right?
    What about the coolant sensor on the manifold? Could that be fritzy?
    I'll try the fan thing but seems to me it's always blowing pretty strong -- just breezy not jet engine like.
    I wonder if the parts store sent me a bad stat 'cos I'm pretty damn sure it's on right.
    smack
     
  9. smack

    smack 1/2 ton status

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    Okay, I just spent the last two hours reading the archives here on fans and clutches.
    My truck does NOT overheat if I let it sit and idle forever so I know at least the fan is spinning, BUT when the engine is off , cold or hot it does NOT spin "freely" meaning that if I put a finger on it and spin it it won't budge, but if I grab it and spin it it will move with slight resistance.
    Now, does THAT mean the clutch is stuck on??
     
  10. heavy4x4

    heavy4x4 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I'm not apt to suspect it's the temp sender since it started immediately after installation, but just in case, where is it?. The unit on the driver's side block is the knock, right?

    [/ QUOTE ]

    Knock sensor is on passenger side.
    Temp sender for gauge is located in between front two cylinders in the block on the drivers side.
    Temp sender for computer is located on top of intake manifold next to thermostat housing.
     
  11. HarryH3

    HarryH3 1 ton status Author

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    It sounds like your fan clutch is working properly. There should be some drag when it's cool. /forums/images/graemlins/cool.gif

    The problem with the engine running too cool has to be with the thermostat. You can NOT overcool these engines with the fan. The coolant in the radiator can be 10 degrees, but if the thermostat is working correcly then the engine will still stay at or very near the temp of the thermostat. The thermostat keeps the cold coolant in the radiator until the engine needs some of it.
     
  12. smack

    smack 1/2 ton status

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    Well, I just replaced the thermostat with another 160 thermostat and still the engine stays at 110.
    ????????????????????????????
    I don't believe the fan is even coming on.
    Now, granted it's cold outside but still.
    ???????????????????
     
  13. smack

    smack 1/2 ton status

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    Great, thanks.
    BUT, how would I know if the guage sender is bad? Seems to work well, but it just won't go above 110.
    If the computer sendor is bad, what would be the symtoms?
    TIA,
    smack
     
  14. smack

    smack 1/2 ton status

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    Alright, just did the stove-top test on the thermostat that I pulled, and it worked fine.
    Therefore, how in hell is my engine no heating above 110?
    The fan does not appear to be even turning on so I guess all that can be left it I've got a bad temp guage sendor.
    Would I be doing any harm if I left it alone? I seem to recall that pulling that sendor leaks out a hell of a lot of coolant.
    smack
     
  15. heavy4x4

    heavy4x4 1/2 ton status

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    Since it's an electrical sender...you could check the resistance reading. If you want those numbers...I can try to find them.
    I doubt it would be the computer sender. That just tells the computer whether the engine is cold or not...and if it is cold, the engine should dump in more gas.
     
  16. smack

    smack 1/2 ton status

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    Well, I'm thinking it's not worth replacing the guage sender just yet because of the mess it makes when you pull it.
    See any reason why keeping it in there would be bad?
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Pop the radiator cap when the engine is up to operating spec (watch out for the hot spewing fluid if you don't have one of the lever operated caps) and stick a meat thermometer or equivalent in the coolant. First off, if there is no pressure built up in the radiator, after you've been driving for awhile, then you really are over cooling the engine somehow.

    If it's really 110, I don't think thats hot enough to even burn your finger, certainly not like 160 would.(real scientific test there lol) If your engine is really at 110*, you should be able to put your hand on the intake and not feel pain. My intake at 195* is hot enough that you don't want to touch it more than a couple of seconds.

    You can pull the fan off and watch the idle temp, but if you suspect a bad gauge, I would not do this, as the temp could go critical and you wouldn't know it until steam starts pouring from the engine.
     
  18. wrathORC

    wrathORC 1/2 ton status

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    If you grab on to the fan with two fingers and spin it the fan should get about a quarter turn. This is with everything cold. If your fan was stuck on you'd know it. It'd be so noisey and so windy you couldn't stand it.

    It takes my truck about nine minutes to get from 10° to operating temperature.

    I'd check to make sure your sender is plugged in good. It works off ground so if you touch the wire to ground it'll peg the gauge. I'd pull it out and clean it. I'd also clean the contact for the wire. If antifreeze doesn't come out I'd stick a screwdriver in the hole to get the crud out of the way.

    If your motor is running normal you won't be able to touch the radiator hose without severe discomfort. Also, do the radiator cap thing I said earlier.
     
  19. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I think your should take the truck to a local shop that has a "laser thermometer". Get them to take a reading of your thermostat housing once the truck is all warmed up.

    I use a laser unit for checking the temperature of fusion irons at work. It also comes in real handy when I swap out a thermostat and want to double check that it's working correctly.....
     
  20. smack

    smack 1/2 ton status

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    Well, when I pull the radiator cap there IS coolant flowing, hot or cold. It seems to be coming from the heater core feed just below the cap.
    When the engine is hot I can grab the upper hose without discomfort --&gt; it's warm but not unbareably hot. The t-stat housing is unbearably hot though.
    Hot or cold it seems the fan will spin freely (with resistance).
    I'll try disconnecting the wire at the sendor and see what that does.
     

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