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Overheating issues

Discussion in '70-Series Tech' started by Lomoski, May 16, 2018 at 2:17 PM.

  1. Lomoski

    Lomoski

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    Hello guys!

    So I have a kzj78 Prado with a 1kz-te and just over 272k km. I just replaced my water pump, put a 78 degree thermostat in and did a flush and put 60 percent Toyota glycol in. This is my first summer owning the truck, with AC on low and going up even a small hill my gauge starts to climb. Knowing that these things like to crack heads it makes me pretty nervous! I have read about the viscous fan clutch needing new oil and that you can adjust the temperature the clutch kicks on at. I am going to pick up some silicon oil for the fan clutch but I'm wondering what valume to put in the clutch and how to adjust the temperature it kicks on at. Any other suggestions? Am I missing something?

    Cheers guys.

    Lomo
     
  2. GTSSportCoupe

    GTSSportCoupe

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    As far as changing out the fan fluid, follow the procedure by the original poster in this thread: Blue fan clutch mod

    Have you seen my fan upgrade thread? In my experience, this has been the best modification for cooling. Not sure what part number fan is on the 1KZ, but if it looks like my 2LT fan, you'd benefit greatly upgrading to the 1HZ/1HDT fan (as I did). LJ78 Big Fan Upgrade #2

    A 78 degree t-stat is going to make your engine run less efficient. What you need is an 88C t-stat, that opens fast, and opens wider than stock. I highly recommend buying a high-flow thermostat from Tridon (australia). You can find them on Ebay Au.

    What shape is your cooling system in otherwise? Is the rad clean inside and out?

    Finally, if you REALLY want to protect that cylinder head under all circumstances, I recommend an upgrade to Evans Waterless Coolant. It doesn't boil until 180C. It also prevents localized boiling around the pre-cups in the cylinder head which is what causes the head to crack eventually.

    And remember, try to drive as much as possible with the rpms up and torque converter locked on those hills.
     
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  3. Lomoski

    Lomoski

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    Thanks for all that GTS. I will do the clutch fluid replacement and adjustment to start.

    Curious why the 78 degree t stat will make a difference in efficiency? I'm sure it makes sense, but having just put new coolant in I'm reticent to drain it all out again already! I'll try to get a new t stat on order.

    I've been trying to use high revs and keep the torque converter locked but it seems to make the temp spike faster.

    The cooling system seems to be in good Nick otherwise. I did a flush before putting in the new water pump, rad looks free of too much deposits. I'm pretty confident the fan isn't working as it should though, it seems to always be spinning but not really cutting in and out

    As always, much appreciated.

    Lomo
     
  4. GTSSportCoupe

    GTSSportCoupe

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    If the fan is working right, you'll know it. It literally starts roaring.
     
  5. Lomoski

    Lomoski

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    Check, no roaring heard ever. Will be rebuilding and afjusting tomorrow!
     
  6. morganism

    morganism

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    did you burp the cooling sys on a steep hill ? Run the heaters for a half hour? May have a bubble in the sys.
     
  7. Lomoski

    Lomoski

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    Didn't burn the cooling system, not sure what that even means, but I've had the heater run on high for more than a couple hours. The level hasn't changed at all in the rad or my overflow. I think the fan is the issue to be honest. I've never heard it really engage. It has 250k+ km on the original oil in it. I'll give that a try first and go from there.

    Cheers!
     
  8. Gun Runner 5

    Gun Runner 5 KI4CMQ SILVER Star

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  9. Lomoski

    Lomoski

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    Auto correct... Meant burp. Still not sure what that means though.

    Cheers
     
  10. GTSSportCoupe

    GTSSportCoupe

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    Burp = getting the air out. Should happen over time naturally as the air gets pushed out your over flow when the system is hot, and coolant is drawn back in when the system cools. After a few cycles the air is gone.
     
  11. Lomoski

    Lomoski

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    Thanks,

    I've had it hot and cooled off at least a dozen times since I replaced the fluid. No change in levels so I think it's good.

    Going to do the viscous clutch tomorrow.

    I'll let you know if it changes anything.

    Cheers
     
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  12. Lomoski

    Lomoski

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    So just to follow up. Did the blue hub mod. Adjusted to 95 degrees and replaced the oil with 7k CST silicone oil. Had to adjust quite a bit to get it to open at that temp so it was definitely opening at too high of a temp. The oil was the colour of honey as well so I'm guessing it had broken down substantially. Haven't taken it for a long drive but I can actually hear the fan engaging now. So I'll try it with 7k and if it needs more cooling I'll put in 10k.

    Thanks for the suggestion gtssportcoupe I never would have figured that out on my own!

    Cheers

    Lomo
     
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  13. MalcolmY

    MalcolmY

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    I just read the blue mod post, but he didn't explain what 7k and 10k are. Would mind explaining whatwhat that is our why would one choose either? Thank you
     
  14. coldtaco

    coldtaco

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    7k and 10k is the thickness, or viscosity. 10k being thicker than 7k.