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Why my Engine Temp. Fluctuates.

Old 04-15-2019, 06:43 AM
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Why my Engine Temp. Fluctuates.

I have a 1994 Toyota Pickup 3.0L. This Morning while driving to work I noticed that my engine temp gauge was going from normal to hot and it would stay at hot for a couple second then would go to normal then warm and hot.
Radiator Fluid level is good. My ride to work is about 15 Minutes All HWY Speeds 65Mph. No Engine Light also.
Can any one help me out with this.

Thanks,
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Old 04-15-2019, 06:59 AM
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While you could have a bad gauge sensor (or associated wiring), my first guess would be a sticky thermostat. If I'm right, you should change it sooner rather than later; if it sticks closed for a "long" time, you could damage the engine.
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Old 04-15-2019, 07:03 AM
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That's what I was thinking a bad thermostat. Is the thermostat easy to change?
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Old 04-15-2019, 07:37 AM
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Yes. No. It depends on what you think is easy. Compared to a lot of other things: easy.

But all answers are found in The Good Book. http://web.archive.org/web/201311071...10thermost.pdf Read through this and make your own decision.
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Old 04-15-2019, 07:55 AM
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Scope103, If its not my thermostat what else can cause this to happen? Just thinking ahead.
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Old 04-15-2019, 01:50 PM
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Haven't changed one in a 3.0 but usually they are pretty easy as long as you don't twist off a bolt (ask me how I know). Very easy on a 22re or 3.4, Toyota was usually pretty good at designing stuff to be worked on. Thermostats are about $10, overheating a motor can be real expensive, I would pick one up and change it before I drove home if I was you, I've changed them in several rigs in the parts store parking lot.
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Old 04-15-2019, 04:04 PM
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As scope said, this is most likely a sticking tstat. But while you are changing it, pull your temp sender and clean the body and threads really well to shiny metal. There are 2 temp senders, one for gauge one for ECU, so might as well clean both. Also an air bubble in system can cause temp swings, but normally I think the air bubble would cause you to briefly read low on gauge, not high. Either way, burp system very well. There are lots of tips on how to burp your system on here.
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Old 04-15-2019, 06:48 PM
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Another vote for thermostat. I suffered with a similar problem on daily driver Honda for a while. Going down hills at highway speed, the temp gauge would drop. Thermostat was never totally closing.

Last edited by Melrose 4r; 04-17-2019 at 05:41 AM.
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Old 04-16-2019, 04:34 AM
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It was the Tstat Fellas. Also cleaned the senders and flushed the radiator with cleaner. The Yota is back on the road. Thanks Fellas for the help!!!
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