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Temp gauge fluctuating


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I have a 99 Legacy L wagon, 2.2l. Last Saturday while driving home from a 40ish mile round trip, I noticed my temp gauge had risen to about 3/4 to the "H". It usually sits just below halfway. I noticed that when I turned the heat on, it dropped back down to normal. I drove it for another 3 days without the gauge rising above its normal level. On Wednesday, I noticed that it had begun rising slightly above halfway again, but it would fall on its own without me turning on the heat. Since then, it continues to occasionally rise just above halfway and go up and down in its own.. What could be causing this to happen? Could I have introduced air into the system when opening the rad cap to check my coolant the week before? (The car was off when I took the cap off and I started the car with the cap off.) I know the 2.5s are known to blow HGs, but how common is it for 2.2s to blow HGs?
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Pretty uncommon if the coolant has been cared for.

 

When you checked was the radiator full to the top with some in the overflow bottle as well?

 

If it was down a deal and you have a tiny leak somewhere it could have gotten enough air in it to act like that. How long since you last checked the coolant level and know it to have been full?

 

If it behaves over the next couple weeks/few hundred miles, great. If the level goes down again, then you have to find out where it went. Also, watch your oil every other day or so during that time to make sure it isn't getting coolant in it.

 

If you don't feel like waiting, there is a chemical tester you can get at a parts store. You feed it a sample of your coolant from the radiator and put in the reagent and watch for the color change.

 

But it is probably more likely that you have a tiny external leak. Besides the main hoses there are the ones that run to the heater, and some others that feed a little heat into the throttle body for cold weather. Then there is the drain at the bottom of the radiator and the o-rings for the crossover pipe. At our age any of these could leak a tiny amount.

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Pretty uncommon if the coolant has been cared for.

 

When you checked was the radiator full to the top with some in the overflow bottle as well?

 

If it was down a deal and you have a tiny leak somewhere it could have gotten enough air in it to act like that. How long since you last checked the coolant level and know it to have been full?

 

If it behaves over the next couple weeks/few hundred miles, great. If the level goes down again, then you have to find out where it went. Also, watch your oil every other day or so during that time to make sure it isn't getting coolant in it.

 

If you don't feel like waiting, there is a chemical tester you can get at a parts store. You feed it a sample of your coolant from the radiator and put in the reagent and watch for the color change.

 

But it is probably more likely that you have a tiny external leak. Besides the main hoses there are the ones that run to the heater, and some others that feed a little heat into the throttle body for cold weather. Then there is the drain at the bottom of the radiator and the o-rings for the crossover pipe. At our age any of these could leak a tiny amount.

 

I checked the coolant yesterday and the radiator is full, with some coolant also in the overflow bottle. I was told by the mechanic that he thinks my radiator may be the issue, perhaps a clog or pinhole. He wants me to drive it, but keep a close eye on the temp as to not let it overheat, and to try to establish the conditions that make the gauge rise. As it stands now, it only goes slightly above halfway, and that is only when I drive at least 20 min or so. When i drive more than 20 min, it goes up and down on its own, between normal and a notch or two above halfway several times a trip without me turning the heat on. The one time it made it to 3/4 was a week ago, after coming off the highway during a 40 min drive home. This time I got the gauge back down to normal by turning the heat on. I'm afraid to take it on the highway again..

 

Is it possible to introduce air into the system by taking the rad cap off and starting the car with the cap off? I did this a few days before all the foolishness began. Everything was fine until then.

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Getting air in the system shouldn't be possible just by taking the cap off under normal circumstances.

 

Sometimes you can burp air out by taking the cap off and filling with the car head up a very steep hill. The tipping lets the air come to the cap. So I suppose in a technical sense you could maybe let air in by pointing down a very steep hill while you checked, but realistically I don't think you could find a hill steep enough for this, and I don't believe anyone would park on such a hill never mind do minor checkups.

 

I agree with drive it and eagle-eye it. You can work your way up from minor trips to longer to highway. The needle can get pretty close to the top without damage as long as you don't just let it stay there. It's mostly the people that don't pay any attention and don't understand or care that blow up engines.

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Getting air in the system shouldn't be possible just by taking the cap off under normal circumstances.

 

Sometimes you can burp air out by taking the cap off and filling with the car head up a very steep hill. The tipping lets the air come to the cap. So I suppose in a technical sense you could maybe let air in by pointing down a very steep hill while you checked, but realistically I don't think you could find a hill steep enough for this, and I don't believe anyone would park on such a hill never mind do minor checkups.

 

I agree with drive it and eagle-eye it. You can work your way up from minor trips to longer to highway. The needle can get pretty close to the top without damage as long as you don't just let it stay there. It's mostly the people that don't pay any attention and don't understand or care that blow up engines.

 

Thanks for your input doublechaz! So it's highly unlikely that I introduced air into the system. I was hoping it could be something simple like that, but oh well..

 

To be honest, I wasn't happy to hear that I would have to drive it like this for a while in order to figure out the issue, however I do understand that just throwing parts at it isn't really a smart idea. I feel better hearing from you that it will be fine as long as I keep an eye on the gauge. I think I feel more comfortable with easing into longer trips now.

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The people that never look at the gauge and drive until it stumbles or shuts off are the ones who end up with really broken stuff.

 

You know about turning the heater on to help out, and you have enough concern to stop driving it if the needle runs away, so you'll be fine.

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