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Coolant Temp Question
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Old 02-15-13, 07:54 AM   #1
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Default Coolant Temp Question

Just a quick question if you guys wouldn't mind humoring me.

R/T Tuning bled and filled the car up with Glycol coolant about a week ago. After a couple of 2+ hour drives I wouldn't imagine all the air bubbles are out. I also know we don't have the most accurate system, but when is the needle considered to be "high" on the temp gauge. The needle today (~45*F) seemed to be a tad higher than normal, but no where near the middle of the gauge by any means. Just a tad higher than it normally sits right above the first tick. Now, if it is reading slightly higher during 45* weather, I am a bit nervous for when it becomes 85* weather. Also I my drive I did notice the temp needle drop a bit from it's normal position then rise back up. Could this have been from the fans turning on when I was in traffic and then started driving? I know this isn't a huge deal and may seem like nothing, but I want the car running healthy for the summer. Thanks for any help guys. I may take a drive again later today (car was sitting for 4 days) and try to get a pic of what I think might be the needle being a tad high on the gauge.
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Old 02-15-13, 08:00 AM   #2
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Default Re: Coolant Temp Question

High is the second mark on the gauge and up. Anywhere in between those two marks is normal operating temperature. Anywhere below the first mark is considered cold.
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Old 02-15-13, 08:26 AM   #3
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Default Re: Coolant Temp Question

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Originally Posted by jdblock View Post
High is the second mark on the gauge and up. Anywhere in between those two marks is normal operating temperature. Anywhere below the first mark is considered cold.
Did not know that. So even if you're right below the second tick as opposed to right above the first tick, that's still considered normal operating temp? Or is that excessively high?

Any issues with Glycol coolant?
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Old 06-24-13, 10:13 PM   #4
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Default Re: Coolant Temp Question

Not very educated on Subaru coolant temps other than to say if our needle moves from what has been typical in the last 140,000 miles...I would be concerned. Always just a tick above the first line.

The Cobb AP does have an option to watch actual temps...certainly far more accurate than the analog gauge. Mine touched 210 once, if I recall correctly.

Hope that helps.
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Old 06-25-13, 08:55 AM   #5
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Default Re: Coolant Temp Question

The stock gauge sucks.

If you have an AP I would keep track of it that way. Anything from 180 - 215 I would consider normal.

Like B said though, unless your getting above that second line I wouldn't worry about it. If your getting large temp fluctuations you need to re bleed your system.
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Old 06-28-13, 09:04 PM   #6
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Default Re: Coolant Temp Question

Sounds like you had air in the system after the coolant change. How is it now? The upper end of the stock gauge is approx 230 deg actual coolant temp...once it gets to the top of the gauge its closer to 240 deg. It can get that hot during the bleeding process but should quickly cool down as coolant is added to replace the air.

At the point you are describing on the gauge you are probably seeing 207 degrees and then the fans come on and drop it back down, but it shouldnt go below the first mark on the guage once its has reached operating temp. Even at 187 degrees my stock gauge stays a tick above the first mark on the gauge.

Your temps will spike with air in the system, but as long as your not driving it for miles like that, it wont hurt anything; the coolant shouldnt get hot enough to boil or boil out of the overflow...it it gets THAT hot then its probably exceeding 250 degrees and that is hot enough to damage the engine if your driving at speed. Pull over and let it cool if it gets to the top of the gauge and get it somewhere to bleed the cooling system.

I thought I read on here that the Subaru ECU has a failsafe and will shut the engine off at a certain overheat temp?? But I wouldnt worry if you dont hear the coolant boiling or if it only got hot for a short period of time and you werent on the highway or driving for miles like that. But it's best to pull over and let it cool to insure that you dont get to a temp that can boil the coolant

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Old 06-29-13, 11:05 PM   #7
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Default Re: Coolant Temp Question

i had low coolant after doing work on the turbo and reading from my AP the temp climbed up to 230 at red lights but when i went over 45 it cooled down to the normal 198. filled it up and bleed the system and its always at 198. so you shouldnt worry about being to hot for a short amount of time. the other guys on here also have some good info
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Old 02-15-15, 09:15 AM   #8
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Default Re: Coolant Temp Question

Yooooo bringing this tread back, I recently replaced my radiator at the 105k service to an aluminum rad from Mishimoto. Is it normal for my temp gauge to fluctuate lower at times? This happens usually when I'm either goin downhill on a highway, or I sometimes have good throttle modulation on a flat surface on the highway 6th gear @ 80mph. It does not get higher than the normal op-temp, but at times it dips just below the first notch mark. Also will this lowered temp cause my car to run rich til it's back up? Thanks all.
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Old 02-15-15, 11:14 AM   #9
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Default Re: Coolant Temp Question

Define "fluctuate", do you mean a constant "up down up down" motion on the same down hill stretch or it'll move up to normal op temp while driving under load and when going down hill the temp needle (or gauge reading) drops but returns to "normal" when resuming putting the engine under load again? As for running rich, watch your AFRs. Rich is better than lean, but unless I'm missing something the coolant temp shouldn't have an affect on fuel trims, AFRs, etc.
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Old 02-15-15, 03:09 PM   #10
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Default Re: Coolant Temp Question

Quote:
Originally Posted by ptak View Post
Define "fluctuate", do you mean a constant "up down up down" motion on the same down hill stretch or it'll move up to normal op temp while driving under load and when going down hill the temp needle (or gauge reading) drops but returns to "normal" when resuming putting the engine under load again? As for running rich, watch your AFRs. Rich is better than lean, but unless I'm missing something the coolant temp shouldn't have an affect on fuel trims, AFRs, etc.
Hey, thanks for reply... Ehh I think "fluctuate" might have been the wrong word... Idk maybe. Yea when I'm not under load, it seems to drop(the temp needle) a tad bit, even on flat surface. And yes it comes back up after several seconds of mild load. Obviously 70-80 mph highway it does stay steady above the first notch line, but goes down when I'm cruising on a down hill. My old Civic or my wife's Toyota RAV4 never showed any temp "fluctuation" in accordance to drive load...

I really don't beat on the car since I'm usually carrying my daughter in the back. I've read in other threads about "racing" thermostats opening early and keeping the temp lower than "operating temp". It was stated that people will suffer from running rich because the ECU is detecting the less than normal operating temps. But I had the regular Subaru thermostat installed 2k miles ago with my service. I don't have an AF gauge or an accessport to determine any of those factors. Our cars run rich naturally anyway right? Anyway thanks again. I'm still slowly learning the basics to STIs
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