Why would temp gauge swing up then back down?

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Car runs fine, but it does.

Air pocket?
Something worse?

This time, it went up to about the "A" on.my temp gauge's range of "NORMAL," back down to the N, stayed low a little, now is fine.

?
 
If this is your Taurus, it's normal. Mine travels back and forth all day long. I used to have a Ford Aerostar that did the very same thing. Don't worry about it - as long as it stays in the "normal" range, you're fine.
 
What was the duration of time during this temp change swing?
Idling at a stop light for a while? Stuff like that can happen depending on the car's gauge. Most car's gauges never fluctuate at all unless there is a problem, whereas some cars have gauges that more accurately tell the true story.
 
Originally Posted By: GreeCguy
If this is your Taurus, it's normal. Mine travels back and forth all day long. I used to have a Ford Aerostar that did the very same thing. Don't worry about it - as long as it stays in the "normal" range, you're fine.


Oh, thank you! Yeah, first car I had that did this!

Now it is stayimg at normal, but im sure it eill wander again.
 
They fluctuate?

Every Ford I've ever driven, at least every one that had a gauge, kept the needle right smack in the middle all day long. Uphill, downhill, heavy traffic, idling, etc... Right in the middle.
 
Originally Posted By: Eddie
Sticking thermostate. My vehicle used to do this once every moring on first warmup of the day. Turned out it was a sticking stat. Ed


yeah the ram in my sig would have the same thing happen. I would be driving alonge and notice the temp heading toward hot. and then as soon as I noticed it would go back down to normal. drove me nuts.

A new Tstat fixed it.

If the cooling system was recently serviced, it could also possibly be a air pocket.
 
Our two '94 Taurus SHO's had temp gauges that told the real deal. I could even see when the thermostat opened on one of them. Our '98 Windstar... not so much. My old '88 Mustang was a bit of a mix of both.

Honestly.. I would just get that thing running half [censored] decent and then drive it until it implodes dude.
 
Thermostat is causing the swinging temps, opening and closing. When your thermostat goes you will know, it will run real cold or real hot. I started getting bigger variations in the Temp Guage, in which my car was running to cool. I replaced the thermostat then, the little rubber o-ring was dislodged and blocking the thermostat from closing.
 
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Bet you will find the coolant in the radiator low,and the level either high or low in the overflow.I vote for air pocket.
 
Originally Posted By: css9450
They fluctuate?

Every Ford I've ever driven, at least every one that had a gauge, kept the needle right smack in the middle all day long. Uphill, downhill, heavy traffic, idling, etc... Right in the middle.


Depends on the age. I think in the early to mid 90s they smoothed them out. I know my 86 Mustang would hover at the extreme end of Normal when coming offf the highway with the AC on and in the heat. Would sometimes poke its way out of the band but quickly come back down. Same with an 87 Escort although that didn't get as far in the Normal range.

I had a 97 Cobra that would run hot on really hot days and it also poked at the end of Normal if the AC was on and the temp was hot outside. But those had marginal cooling systems to begin with (the 96's had overheating issues and Ford fixed them but there wasnt much room under the hood).

After that all the Fords (00 Explorer, 03 Escape, and 10 SHO) all park it smack in the middle no matter what the temp.

I wouldn't worry about it as long as it's in the normal range. Older cars tended to have wild swings in the temps but it's nothig to worry about as long as its in normal.
 
SAAB 900s did the same thing. There was always a little delay before the fans kicked on and the gauge reflected that. If the AC was on and the fans operating the temp was much more stable because one fan ran all the.
 
Originally Posted By: bdcardinal
Your temp gauge is just a light that uses a needle to show the light being on or off. It is not accurate by any means.


Not true. My gauge is as consistent as day and night. I can tell the temperature of the engine to within 5 degrees just by watching the position of the needle. I've compared it to the reading from the PCM and it's dead on. There's no reason a gauge can't be accurate or consistent.
 
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Originally Posted By: NHGUY
Bet you will find the coolant in the radiator low,and the level either high or low in the overflow.I vote for air pocket.
This car seems very tempermental as to whether it sucks the overflow dry, or it just stays there!

I try to quickly open then close the cap after it is shut off, a few times, when it is hot. Is that helping?

And yes, it acts exactly as Eddie says. I probably DO need a new Stat. I'll bet this one is the original.

The question is, is it MALFUNCTIONING. And that answer sounds like a No...

Should I open her up and put in the rest of the Antifreeze?
 
TechnoLoGs I try to quickly open then close the cap after it is shut off said:
No! In normal conditions there's a small vacuum under the cap, when it gets big enough it slurps a little coolant from the overflow tank. Opening the cap removes this vacuum and it has to start over with a couple heat/cool cycles to get back where it needs to be.

In other words, it's a siphon, and it needs a little water to get working. It sets up automatically, except when you mess with it, which seems to be most of the time.
 
PS, more modern cars usually have the computer drive the temp gauge with a huge dead zone in the middle for "normal", thanks to worried drivers complaining.
 
Yep. That's the same reason Ford came out with their wonderful oil pressure gauges.
wink.gif


I've seen properly functioning vehicles have very, very steady temperature gauges. I've seen others have occasional swings, though those swings were predictable. They usually happened under extreme temperatures, such as very hot with lots of idling, with some motion in the gauge when the fan kicked in and out, or under extremely cold conditions, going from an excessive idling situation onto the highway.
 
Need more in terms of the circumstances. If in stop and go traffic on a hot day, I could see such a wide swing. The electric fan kicks on and drops the temp of the coolant. The fan is called for by engine cooling or A/C operation.

If this is happening on the highway at steady speed on a level road, then it may be low coolant, with the temp dropping when there is no coolant in contact with the temp sensor.
 
Originally Posted By: eljefino
Originally Posted By: TechnoLoGs

I try to quickly open then close the cap after it is shut off, a few times, when it is hot. Is that helping?


No! In normal conditions there's a small vacuum under the cap, when it gets big enough it slurps a little coolant from the overflow tank. Opening the cap removes this vacuum and it has to start over with a couple heat/cool cycles to get back where it needs to be.

In other words, it's a siphon, and it needs a little water to get working. It sets up automatically, except when you mess with it, which seems to be most of the time.


I see.

So, if you were me, you would STOP messing with the cap, keep an eye on the overflow, and let it set up that way?

If so, I will just put the rest of the antifreeze in the overflow and take this long drive to PA tonight...

and javacontour, it appeared to do so first warm-up of the day, and knowing its probably original Stat, me as el-cheapo right now hopes it cleans up, but Eddie's description was the best. Though it USED to fluxuate when taking off from lights, but coolant was low and dirty then.
 
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