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Thermostat operating temperature

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Alex, Oct 7, 2002.

  1. Alex

    Alex Registered Member

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    Silly question, but has anyone seen a difference in their operating temperature by switching from the OEM 192/195 degree to a 180 degree thermostat? Someone mentioned that by lowering the thermostat to a 180 that my motor may run cooler. My first reaction was that it should not matter because the function of the thermostat is to stay closed until you reach that specific temperature then it opens. After that, the motor will heat up to whatever operating temperature and driving condition you experience (e.g. towing/wheeling/snow etc). /forums/images/graemlins/confused.gif
     
  2. Sandman

    Sandman 3/4 ton status Author

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    Well, the idea is that the cooling system is good enough that the engine will run at whatever themostate operating temp you put in. Hard use would heat it up higher.
     
  3. txbluethunder

    txbluethunder 1/2 ton status

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    mine depends on where i'm driving. when i'm on the highway and the fan is not working then i stay @ 180. in the city driving from stop light to stop light it heats up to 200 before the fans kick on and then they kick off at 190. so yes...on the highway my engine runs cool enough that the thermostat has to close otherwise it would prob run at 130?
     
  4. imiceman44

    imiceman44 1 ton status

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    It all depends on your cooling system.
    I had an engine with 160 degree thermostat, and it ran most of the times between 165-175.
    Don't do that to a computer controled car though, you will trick the ECM into dumping more GAS and that will hurt your MPG's unless that is what you want for more performance.
    And don't go too low in cold states. I am in CALIFORNIA, I can do that.
    IceMan
     
  5. Stoopalini

    Stoopalini 1/2 ton status

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    A 180' thermostat will make your engine run cooler when driving, but will not effect the temp when sitting idle (unless you have the A/C on).

    The reason is the sensor controlled fan(s). If your thermostat is opening up at 195' now, and your fans are turning on at 220' then off at 200' (just gessing at these #'s), then the motor will maintain a ~200' running temp.

    If you throw a 180' thermo in there, the fans will still be turning on at 220' and off at 200' giving you the ~200' operating temp sitting at idle (or low speed driving ie: 4-wheeling); but when you are running down the road, the air rushing through the radiator will give you a cooler operating temp.

    The reason I said when running the A/C, is because the fan(s) should kick on when you turn your A/C on. So if the thermo opens at 180' and your fan(s) are on at this temp, it'll maintain a ~180 operating temp.

    The best thing to do, is to put in a 180' thermostat and replace the fan temp switch for one that opens at a cooler temp. This would give you a cooler running engine and better performance.

    Thomas.
     
  6. imiceman44

    imiceman44 1 ton status

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    My fan was a solid mount, no clutch fan.
    So it ran all the time and the only thing controling the temp is the thermostat.
    IceMan
     
  7. Alex

    Alex Registered Member

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    My '91 has a clutch fan (manual), the unit is not electrical. As the motor heats up the clutch (spring) engages the fan to turn at the same revolution as the engine.
     
  8. georgiared84

    georgiared84 1/2 ton status

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    I'm running a 165 on mine and it usually runs at 165-170. If I run the AC in hot stop and go traffic it runs about 190. The only time I run something different is when I need to pass emmissions. Then I run the 195 thermostat because it passes better when it's hot. Of course, having an 84, I have the luxury of not having to screw with a computer.
     
  9. Stoopalini

    Stoopalini 1/2 ton status

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    Well, with a clutch fan, you shouldn't have any problems installing a 180' thermostat.
    As long as the temp gets high enough to allow the ECM to switch into closed loop mode, it will run fine.

    I'm not sure what temp the ECM is programmed to go into closed loop, can someone else clarify this?

    Thomas.
     
  10. Z3PR

    Z3PR Banned

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    I don't know if it really does any better, but I run the 160 degree thermostat. But ofcorse, I don't have a computer controle engine either. /forums/images/graemlins/k5.gif
     
  11. Thunder

    Thunder 3/4 ton status

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    Your profile says your truck is computer comtrolled TBI . You should keep the 195 degree stat. That is what the computer is programed for. Going down to a 180 stat probabally wont hurt anything. But for best performance I think it is best to run what the computer is programed for.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Don't waste your time. I'm a little biased obviously, but you won't notice anything at all with a lower thermostat, except maybe lower engine temps. TBI should be fine with 180, but 160 is REALLY pushing your luck, with the ECM and with the engine itself IMO.

    Great, cold air makes more power. Couple that with increased oil viscosity, less expansion (worse sealing) of the pistons in the cylinders, worse fuel atomization, along with incorrect bearing clearances, and decide for yourself if its worth changing from the temp GM has been using for 30+ years.
     
  13. imiceman44

    imiceman44 1 ton status

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    As I said before your truck is computer controled so if you do go lower, the computer will think it's cold and it will richen the mixture to warm it up, and that will make bad feul milage.
    It's actually a trick they use when they put bigger headers and better intakes, and don't want to or can't reprogram the chip.
    If you have a stock engine stick with the stock thermostat.
    IceMan
     

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