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When I first start my car the last few days (A 2008 Toyota Camry that I've had since it was new in 2007, 13 years) the temperature needle ends up slowly climbing past the halfway point all the way to the top. Only then, about two minutes into using it, does it slowly drop. It takes about a minute more until it stabilizes at the midpoint and stays there until I'm done driving my car

This happens, generally, after each time I leave it sitting for more than a few hours. Sometimes it doesn't climb all the way; sometimes it just goes a little above the middle before dropping and stabilizing

The first time I noticed it, I heard what sounded like an extra set of fans kick on when it got all the way up, which quickly cooled it down to the middle

Running the AC might be making it worse – making it go up faster? But it seems to go up regardless of whether the AC is on or not. My AC was recharged (for the first time, I believe) about two months ago...

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    Welcome to Motor Vehicle Maintenance & Repair! Since I'm not a fan of "replace it and see if it helps" type wrenching, I'll ask you a question: Have you checked your coolant levels?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 20, 2020 at 18:12
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    Agree with checking coolant levels first, rather than straight away jumping to things like thermostat replacement. Low coolant gives erratic temperature gauge behavior if the temp sensor is picking up the temp of the hot metal it is screwed into rather than the coolant (not) washing over it (because there isn't a lot of it sloshing around due to low levels) until the thermostat opens. It's also really easy to check, often visually without even removing a cap
    – Caius Jard
    Commented Jul 21, 2020 at 7:17
  • Please also give some info as to where you are, what the ambient temperature levels are like there at the moment etc
    – Caius Jard
    Commented Jul 21, 2020 at 7:26

2 Answers 2

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My first suspicion is with the thermostat. It may be failing "slow" which means it's not opening when it should and it takes the much higher temperature and pressure of the hot coolant to open.

Replace it and I suspect the problem will be solved.

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  • thank you! is that something i could fix myself? i've replaced my own battery, break pads, fuses, some interior electronics, etc., but that's the extent of my automotive work. do you think i should take it in? and if i neglect it for a while, how bad is that in the current state? am i doing longterm damage in doing so?
    – Andi Buch
    Commented Jul 20, 2020 at 20:27
  • If you can replace your brake pads and live to tell, then Yes, you can handle a thermostat replacement. Do not cheap-out on the part, this job is mostly labor. . Read up online, make certain you know exactly which engine you have. Look at your engine, make sure the online pics make everything clear . Buy a gasket scraper tool to save you hours of work. . Before you start, drain enough coolant so the thermostat is above all the remaining coolant, or you will make a big mess. . Replace the coolant with NEW coolant. . Make sure you put the new thermostat in the same way as the one you take out.
    – user792019
    Commented Jul 20, 2020 at 21:50
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    I'm not quite sure why this is getting upvoted so much ... this is a very poor answer. This is typical "Remove & Replace" wrenching, which is absolutely the worst form of wrenching there is. Reason? You are spending money which may or may not fix the problem. What's worse is, you're giving others advice to do the same. You don't know that it's the thermostat ... you're just guessing. You'd be far better off stating "it might be" then telling the OP how to go about checking to see if it is bad. This is very poor advice.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 21, 2020 at 1:30
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 21, 2020 at 17:53
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I am not familiar with the car model in question, but I have pretty much seen the same behavior in other temperature indicators in cars.

This is an artifact of the indicator design and doesn't mean that the engine overheats.

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  • Can you explain why the indicator design causes this?
    – Criticizing Israel not allowed
    Commented Jul 21, 2020 at 11:23
  • Does the indicator design only do this once the car reaches a certain age? (The OP did indicate that this is a recent phenomenon, not since new.)
    – FreeMan
    Commented Jul 21, 2020 at 11:44
  • @user253751 I am not sure. The indicators that behave like this contain a small electric heating element and a bimetal that moves the needle. I think they are made to be extremely inert. In my car, they used to show temp and tank.
    – fraxinus
    Commented Jul 21, 2020 at 13:42
  • @fraxinus If you can't explain it, can you provide a reference which says this is an artifact of the indicator design?
    – Criticizing Israel not allowed
    Commented Jul 21, 2020 at 13:44
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    You'll agree, I think @fraxinus, that there's likely a bit of difference between a 20+ year old Soviet car and a 2008 Toyota?
    – FreeMan
    Commented Jul 21, 2020 at 13:54

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