Possible themostat?

Discussion in 'Gen 1 & 2 - Engine, Exhaust, Drive Line & AC syste' started by Gt489, Apr 20, 2017.

  1. Gt489

    Gt489 SHO Member

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    When I leave in the morning its between 50-60 degrees out. The temp gauge reads just above the blue mark on my 30 mile commute to work. Currently when I leave its 90ish out. About half way home it gets up to the N and O on the gauge. But it will drop as low as the M and A. Im highly suspect of the t-stat. The car in question is my 89 SHO with 99.5k miles. Is the t-stat on SHOsource the right way to go??

    View attachment 4120
     
  2. zoomlater

    zoomlater SHO Member

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    Do you know when the last time the thermostat was replaced? That temp range appears to be normal. My car varies as well. How long does it take to warm up before the fans kick on? If you replace the thermostat, you want to get one that has the jiggle valve (which the one on the Shosource has if you look closely). I usually replace mine with Motorcraft ones if I can find one (RT-1112). I actually bought one off ebay awhile ago that was supposed to be for a Gen 1 car, but I can't seem to find a cross reference for the part number (I think it was RT-1065)
     
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  3. Gt489

    Gt489 SHO Member

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    I can drive 30 miles to work in the morning and its at the top of the blue square. Not sure when it was replaced. Looks as if there may be a drop or two of coolant below the housing as well.
     
  4. sperold

    sperold Last to Know

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    My experience is that thermostats that hunt around the gauge to find a home are on their way out.

    I would change it.

    Before you install the new one, cook up a pot of water on your stove and verify the new one opens properly. That is another thing my experience tells me.
     
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  5. zoomlater

    zoomlater SHO Member

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    So does the needle fall after the cooling fans kick on and off or do it stay in the same place at the end of your drive
    if you are replacing the thermostat, you might consider changing the temp sender as well (its right next to the thermostat)
     
  6. Gt489

    Gt489 SHO Member

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    Yeah it will drop as low as the M or the A
     
  7. Gt489

    Gt489 SHO Member

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    Also it stays down if i leave the a/c on
     
  8. zoomlater

    zoomlater SHO Member

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    Might be a good idea to replace so you will know the history. I usually boil both the new one and old one as Sperold describes. Be careful not to tighten the thermostat housing too tight, its only like 10 to 12 ft-lbs. There are write ups on the forum, just search.
     
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  9. AREA 91

    AREA 91 PA SHO SHOP

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    I would change the thermostat and temp Guage sending unit. Both are cheap and easy to do.
     
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  10. zoomlater

    zoomlater SHO Member

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  11. itwonder

    itwonder SHO Member

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    That indicates it's not likely to be a thermostat issue. Running the AC keeps the electric cooling fan on as long as the car is going less than 50 MPH, stabilizing the temperature. Temp gauge movement when running without AC is pretty normal in the SHO. The cooling fan cuts on when the gauge gets between the N and O.
     
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  12. Tactical SHO

    Tactical SHO Bit Late the the SHO

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    I'm having the identical problem with my 75000 mile SHO my temperature gauge is way cold if I let it idle for a while with the hood closed the fans to kick on but if I turn on the AC and plummets to gauge down and I think it's causing the car to be stuck in warm up cycle. The RPM will increase to warm it up even after driving the car for 5 plus hours
     
  13. sho'noff

    sho'noff shoverdrive

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    It takes less time and money to replace the thermostat than to look for another problem. If you are sure its the problem I would recommend going that route.

    Sent from my VS425PP using Tapatalk
     
  14. itwonder

    itwonder SHO Member

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    I forgot to mention that one thing you might check is to see if it has a 195 degree or a 180 degree thermostat. I prefer the 180 degree. There have been several thermostat threads over the years; I've had good luck with the Autozone Duralast 15878 thermostat + Felpro 35278 seal (it has the jiggle valve).
     
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  15. Gt489

    Gt489 SHO Member

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    I bought a new t-stat. Hopefully ill get it in this weekend. Drove the car to work today and the needle was at M both ways
     
  16. Gt489

    Gt489 SHO Member

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    Blew the upper radiator hose off today on my way home. IMAG2545.jpg
     
  17. Gt489

    Gt489 SHO Member

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    Does anyone know the torque for the t-stat housing?
     
  18. zoomlater

    zoomlater SHO Member

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  19. Gt489

    Gt489 SHO Member

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  20. Gt489

    Gt489 SHO Member

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