Thermostat problem explained
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  • 2 Post By TimmyC
Cadillac STS-V Series Forum Discussion, Thermostat problem explained in Cadillac V-Series Forums; Like many other STS-V owners before me, my thermostat went south on me last week. Just like everyone else, mine ...
  1. #1
    TimmyC is offline Cadillac Owners Connoisseur
    Automobile(s): 99 SLS and Turbo 07 STS-V-Now back to Supercharged
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    Thermostat problem explained

    Like many other STS-V owners before me, my thermostat went south on me last week. Just like everyone else, mine stuck open. Most thermostats don't fail open, they fail closed since that is the default state. There is a stiff spring holding them shut. Being curious I removed it and the problem was immediately apparent.



    There is a gasket that seals the thermostat when it's closed. The gasket rips and the car won't warm up. Eventually you get a p0128 code for a bad thermostat. The response to the code being set is the "Engine Hot-AC Off" message and activation of the electric cooling fans.

    The solution is still the same-new thermostat-but at least we know what is going on now.
    mjs182004 and Guy.Seminerio like this.

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  3. #2
    carter's_sts is offline Cadillac Owners Connoisseur
    Automobile(s): 06 STS-V & 06 STS 4
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    Interesting. Thanks. Still funny that the car acts like it's hot.

    Sent from AutoGuide.com Free App

  4. #3
    deadringer's Avatar
    deadringer is offline Cadillac Owners Fanatic
    Automobile(s): Modified 06 XLR-V
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    Re: Thermostat problem explained

    Is that the stock thermostat that was original to the motor? or a 160deg replacement?

  5. #4
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: Thermostat problem explained

    60,000 mile original

  6. #5
    SCCAForums is offline Cadillac Owners Member
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    Re: Thermostat problem explained

    Yep, mine stuck open as well at 56K miles... I ended up putting in a Lingenfelter 176... with new OEM rubber gasket, and haven't looked back.

    Nice diagnosis!

    Dave

  7. #6
    mike101344 is offline Cadillac Owners Member
    Automobile(s): 2007 STS-V
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    Re: Thermostat problem explained

    DSCN1338.JPG

    My '06 STS-V temp gauge started to read low. I replaced the thermostat myself and all is okay now. No visible problem found. I needed to disconnect the lower hose as the thermostat and gasket were stuck in the housing and needed to be pryed out. If you do it yourself, plan for an hour and be sure you know how you are going to re-clamp the lower hose. I wired mine and then snapped the wire when it was in position, but I suggest an aftermarket screw clamp. I lost about a quart of antifreeze and haven't replaced that yet.

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