Question about 1999 Toyota 4Runner

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Temperature Guage Good Afternoon, I wanted to send you a quick e-mail to see if someone could provide me with some expertise. I presently own a 1999 Toyota 4 Runner 2.7L that has a temperature guage that is gone crazy. This started today, The vehicle will sit and idle at the light and the temp guage will range from normal to hot. Then as one drives through the light the temperature guage will continue but will then max out in the red zone. If someone could reply I would appreciate it. Sincerely, Aaron

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  • kassneram Sep 30, 2008

    good afternoon emissionwiz,

    the truck was not runnning hot, because the 4runner had not been driven for roughly four hours. once the engine was running the temperature guage need kept bouncing up and down like yo-yo. even while just sitting at an intersection...


  • yadayada
    yadayada May 11, 2010

    Is the truck running hot as the guage indicates? #1 rule is trust the guage until you prove otherwise, not to is to destroy the engine.



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You either have an electrical short to the gauge or your temperature sensor on the motor is "out to lunch". Try to manually get your motor temperature with some other sort of thermometer. With a cold engine take the radiator cap off and make sure it is full. Then place a thermometer in being sure to touch the fluid(may sound dumb but don't drop it in the radiator). Start the engine and allow it to come up to operating temperature. Approximately 190 to 200 degrees. Your thermostat should be open at this point and you should notice a flow to the radiator fluid. If the temp holds then you have one of the aforementioned problems. If you have a Haynes manual it should tell you how to troubleshoot the temperature sensor. I believe that I am leaning towards an electrical short of some sort though. An improper ground perhaps. Check and see if there are any fuses that control this system. Once again, the Haynes manual has wiring diagrams that will show you what wires to chase. And it is a chase. wiring problems are hard to find. If the temperature test pans out You may want to buy an after market temperature gauge and mount it up instead. Pull the plug on the old one and be on the road. You may have already solved this problem and I just wasted about five minutes of my life. If not and you have any questions e-mail me at Have fun and be careful. 200 degree fluid is nothing to take lightly.

Posted on Oct 06, 2008


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