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Old 07-15-2012, 05:55 PM   #1
jr4jc
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Default Overheating, Only when air conditioning is on

2005 sti stage 3 with new water pump. have mishimoto racing radiator
and;

Overheating, Only when air conditioning is on.
fans are coming on correctly.
coolant; overflow was empty, upper radiator was full
filled overflow, ran it for 10 minutes with heater on, and it took up half the over flow. still running warm to next line up, not in the red
so next filled overflow again and ran it for 25 minutes with radiatior cap off, and heater on.
didn't take up anymore, didn't see level drop any.
overheating is taking place with easy driving, highway or local doesn't matter, but having the air conditioner on does.

when it overheats it just goes up to the next line, never into the red
when it does if i turn off the air, it cools right back to normal.
could the compressor pull enough to make the water pump belt not turn the water pump correctly.

i have a thermastat and am ready to change it but i can't see how that be the problem???

HELP!!
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Old 07-15-2012, 11:44 PM   #2
jr4jc
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i think its air in the cooling system, after my original post i spent about an hour warming engine and massaging air out of the upper pipe, refilling, letting it cool and warming back up. got a lot of air out of the system.
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Old 07-21-2012, 11:49 PM   #3
jr4jc
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OK anybody that could of figured this one out deserves a prize.
So i take the car back to where I had freon put in the cooling system and WE start looking at everything. no air to speak of in the cooling system, fans checked out, nothing making sense, we get an infared gun and start measuring temps. find a 250 ish somewhere behind the belts and the fans....cant quite figure out where its coming from cause of moving belts and moving fan....raise the gun a little and.......its the alternator. 310 degrees at 2000 rpm.
we disconect and drive it 10 miles with the air on, NO overheating.
wow how strange, got a new one from subaru, holy crap this thing better mow the lawn and walk the dog...but no more overheating.
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Old 07-22-2012, 12:16 AM   #4
rymaggi
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I'm having the same problem. Fans come on correctly. But when I'm stuck in traffic, car starts over heating, but when I start driving again it starts cooling down.
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Old 07-23-2012, 08:55 AM   #5
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Quote:
Originally Posted by rymaggi View Post
I'm having the same problem. Fans come on correctly. But when I'm stuck in traffic, car starts over heating, but when I start driving again it starts cooling down.

Bad thermostat, maybe??
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Old 07-23-2012, 04:56 PM   #6
rymaggi
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Quote:
Originally Posted by motohippy

Bad thermostat, maybe??
Why would a bad thermostat do that?
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Old 07-23-2012, 04:57 PM   #7
treedspeed
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i'm not sure it would.
how about fan switch? though not sure if that would also create the issue op described.
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Old 07-24-2012, 03:28 PM   #8
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Doesn't sound like this is your problem but maybe it leads you in the right direction. If a radiator is getting clogged and doesn't let enough flow through it, having the extra thermal load (or increased air input temp) from the AC condenser can make the car overheat.

Also a broken thermostat that's open (or if the thermostat is missing) will allow for too high of a fluid flow through the block limiting how much heat the coolant can absorb and transfer to the radiator.

Hope it helps, good luck!
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Old 07-25-2012, 04:30 PM   #9
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Quote:
Originally Posted by SubyMass View Post

Also a broken thermostat that's open (or if the thermostat is missing) will allow for too high of a fluid flow through the block limiting how much heat the coolant can absorb and transfer to the radiator.

Hope it helps, good luck!

Was wondering why my car was running hot (right around red zone). Removed a failed thermostat on a trip into NYC, figured it'd just run colder without it. Was actually starting to think it might have been a failing water pump.

Will have to get a new one and see if that helps.
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Old 07-26-2012, 03:06 AM   #10
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It has been super hot too....My jeep does it sometimes with the AC on...
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Old 08-08-2012, 10:30 PM   #11
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after new alternator, because the old one was overheating when airconditioning was on, had NO overheating issues until;
when it is 100 degrees or very close to it, like 97 and over, the temp gauge rises but again only when the air conditioning is on, AND; the temp rises to 222 degrees. it looks bad on the gauge but my accessport shows 222 degrees.
QUESTIONS; is 222 TOO warm or ok
it never ran warm like this before??
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Old 08-09-2012, 02:12 AM   #12
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under 95 degrees = no problems.
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Old 10-01-2012, 09:08 AM   #13
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is 222 TOO warm or ok
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Old 10-02-2012, 12:43 PM   #14
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I had this problem recently in very hot 100+ temps in traffic. I checked the intake air temp on my AP and it said 180 deg. Turned off the ac and it immediately dropped, but I had cooked my Grimmspeed Therm in the process. Your only option is to probably go with an all aluminum radiator, and that may not even do it. It may be a limitation on the stock cooling system. The ac compressor may be putting too much of a load on the engine for it to overcome in really warm, slow speed conditions.

222 is not TOO warm, but your rad fans do turn on at about 210 when the ac is not on. So the system wants to see a lower temp than that.
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Old 10-04-2012, 10:29 AM   #15
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Right, i agree that 222 is not TOO warm, but is IS warmer than the stock system is designed to run. Granted you don't have a "stock" system but i don't see any reason why it would be running warmer than designed.

WRXSD, IAT of 180+ degrees in hot traffic is completely normal for a heatsoaked engine. I don't see how this would have any impact on your thermostat. OP already has a mishimoto radiator, IE all aluminum. A completely stock cooling system should have no issue dealing with ambient temps up past 115F under normal load. I have done plenty of AC- on driving in these temps with no issue...until my thermostat failed eventually, but not related to temperature i don't believe.

If either of you have a protune, check your AC ON idle speed. It should be ~1100 rpm IIRC.
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Old 10-04-2012, 11:10 AM   #16
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possible sticky thermostat. and 222 IS HOT! the fans come on at 207 so .... its supposed to max around there and GO DOWN in temp. not hold till 222!!! do you have any extra volume of coolant in the system? i think our systems dont have enough coolant volume to keep it cool. especially with ac.. and some 100+ temps.
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Old 07-29-2013, 05:31 PM   #17
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I am researching my own A/C issues and was just going to give you what happened to me with your issue if your still having it OP.
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Old 07-30-2013, 11:32 AM   #18
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Why not start with the simple stuff? Take the fan out and reverse spray your radiator (with a hose) to get the gunk out of the fins.
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Old 07-30-2013, 10:46 PM   #19
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i have the same problem, car runs great but as soon as i turn the ac on my temp increases to about 220. I'mm to scared to blow my head gaskets so i just shut off my a/c. My car is fully built with a fluidyne radiator, mishimoto fans and a huge ams fmic. What i think is going on is that the ams fmic takes up so much space that the fans cant pull enough air through to cool the engine. i was thinking to add two push type fans in front of the condenser to push more air for the mishimoto fans. what do you guys think?
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Old 07-31-2013, 06:19 PM   #20
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My problem came back even after replacing the alternator which i thought was the culprit I have changed the thermostat again and flushed and cleaned everything again and while doibg that found my radiator looked slightly deformed and got doing a little research
I have replaced the radiator and so far no problems overheating with air conditioner
I have told the story too many and never really understood till now what I think happened but here goes
it was last summer hundred degree day driving around Nashville after work had to go an hour out of my way on my way home hundred degrees air running the whole time working okay but i was a little warm in the car and temperature gage running right at normal I head home stop and get gas airs still running the whole time temp gauge still running okay and my car is filthy I go through a car wash a touch free car wash and from that moment on when I turn the air on and it was over 90° the car would run warm
I I'm thinking that the cold water of the carwash hits my very very warm aluminum radiator and it expanded and deformed
when I took it out I could not see light through the radiator and the top and sides were slightly
like something had happened catastrophically to it
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Old 08-01-2013, 08:19 PM   #21
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Well I had the overheating issues with my aluminum radiator which came with slim fans. I found that all slim fans come as a 2 wire circuit and my factory 06 was a 4 wire. So soon as I put the original fans back in it worked the way it's supposed to.

I hope your issue doesn't come back! Now if I can just figure out why my relay to my A/C won't energize to send power to my compressor...my a/c would work. :/
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Old 08-01-2013, 08:20 PM   #22
MULEZSTI
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Oh also my overheating was just when a/c was on. Never overheated with it off.
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Old 08-02-2013, 03:46 PM   #23
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If you guys are running anything but the OEM Subaru T-stat it is likely your issue if you don't have air bubbles in there. We've installed probably 3000 T-stats in the past 12 years of working on Subies. The only ones we've seen fail are non-oem ones. Stant, NAPA, GrimmSpeed, etc. They all end up failing.

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Old 08-02-2013, 04:05 PM   #24
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look at the hose that goes back from the coolant reservior to the pump(that hose goes under the intake manifold) sometimes it clogged from rust and dirt and cause overheating problems.
in afriend car that overheat we replace almost every component in the cooling system till find this problem.
this is my 2 cents...
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Old 08-08-2013, 10:04 PM   #25
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Quote:
Originally Posted by waylouderthanyou View Post
i have the same problem, car runs great but as soon as i turn the ac on my temp increases to about 220. I'mm to scared to blow my head gaskets so i just shut off my a/c. My car is fully built with a fluidyne radiator, mishimoto fans and a huge ams fmic. What i think is going on is that the ams fmic takes up so much space that the fans cant pull enough air through to cool the engine. i was thinking to add two push type fans in front of the condenser to push more air for the mishimoto fans. what do you guys think?
Problem solved, finally, the problem is because in this hot Florida weather the slim fans just wont cut it. The stock fans have two speeds so i put back a stock set of rad fans and cars works perfect. Hope this helps someone. For more info, pm me.
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