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Old 09-07-2020, 03:06 PM   #1
855T
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Default Overheat on freeway

2010 WRX, ~70k miles, on a Stage 1 OTS tune from Cobb, timing belt + thermostat + water pump + radiator hoses + radiator replaced about 6 months ago.

It's been hot af in LA lately. I was averaging about 80 on the freeway a couple weeks ago and noticed the A/C cut out, checked the engine temp gauge, and saw it was about 3/4 of the way to H. Turned off the A/C, slowed down, and turned on the heater, got it back to mid-gauge in maybe 2 minutes. At the time, the external temperature gauge showed 108 F.

Yesterday, closer to 115 outside, going 70 and saw the gauge start to creep up, so I killed the A/C - wasn't enough. Again, turned on the heater, temp dropped right back down again.

No signs of coolant leakage, oil looks and smells like oil, coolant looks and smells like coolant. It is, however, green and not Subaru Super.

People live in Arizona, so I assume this is not typical behavior for this car. I'm gonna hassle the shop that did the work, but anyone have a guess as to what's most likely? Failure to burp the system effectively? Bad coolant or coolant ratio? Thermostat? Effing head gaskets?
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Old 09-07-2020, 05:51 PM   #2
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Have you logged coolant temps on the accessport to confirm the temps are indeed excessive? Are the fans kicking on? They should turn on at 205 deg.
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Old 09-07-2020, 08:50 PM   #3
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Ran a quick log today...I saw 205 on the freeway but wasnít driving very long and itís close to 20 degrees cooler today. Iíll try and get a better log when it gets warmer.

Whatís a reasonable max? 210?
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Old 09-08-2020, 09:31 AM   #4
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Check for air in your coolant lines.
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Old 09-08-2020, 12:46 PM   #5
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I'll try a burp...a funnel is arriving tonight.
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Old 09-08-2020, 12:50 PM   #6
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Don't need a funnel. Just open your reservoir tank and squeeze the large curved Radiator Hose a few time. If there is air you should see/hear it bubble out in the reservoir tank. When you squeeze, just keep a eye on the tank for the coolant not top over flow. This hose. Not my pic. Keep in mind to do this with your eng off.

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Old 09-08-2020, 01:06 PM   #7
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Bad rad caps can cause some pretty funky cooling system issues, like what you're experiencing, and are a service item many people forget.

IIRC, Turbo tank is 108kpa (or ~1bar) and rad cap is is like 137kpa (or 1.3bar).
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Old 09-08-2020, 01:40 PM   #8
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I'll give the hose a squeeze. The caps (rad and expansion tank) are new as well, but are cheap enough to try replacing.
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Old 09-08-2020, 06:21 PM   #9
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No obvious air on the hose squeeze. I'll try with the car running and the funnel in place, as well.
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Old 09-09-2020, 09:24 AM   #10
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Did this happen before you changed the thermostat?
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Old 09-09-2020, 12:23 PM   #11
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I never saw it before the cooling system was overhauled. Doesn't mean it didn't happen, but I'm fairly confident this is a new problem.

I ran a longish datalog last night - coolant temps as high as 207 during sustained cruise ~85 mph over 15 miles or so.
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Old 09-09-2020, 01:19 PM   #12
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Why was the coolant system overhauled? I would check, maybe change, the thermostat again and reflush with new coolant. Why did you change your water pump at 70k? Was it changed to a OEM one or upgraded to a different model? Check the Radiator fins to make sure that there is nothing stuck in them preventing air from going through. Why was the radiator changed? Was there a issue or did you upgrade it to a after market?

Last edited by BlackFighter; 09-09-2020 at 01:25 PM.
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Old 09-09-2020, 01:44 PM   #13
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make sure your caps are on the correct positions...the round one on the radiator the oval on the upper one
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Old 09-09-2020, 02:29 PM   #14
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Caps are in the right spot.

Car was due for a timing belt and needed hoses, so I had them do the water pump (OE) as well, and they recommended an OE replacement radiator given that everything else was being replaced.

Thermostat seems most likely at this point.
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Old 09-09-2020, 03:08 PM   #15
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Well first thing first the shop BSed you in to changing parts that were perfectly fine. Unless the radiator is leaking or damaged there was no reason to replace it. Especially at 70k miles. Was the radiator a dealer part or a OE part from autozone? OE does not always mean it comes straight from the dealer. It just mean that the specs are the same as the dealer. Was this done at the dealer?

At this point if everything is fine with the coolant system and you can't fix the problem I would just take it back to the shop. Tell them:

" Look, before you guys touched the car the cooling system was fine, as soon as i picked it up after you, it started to have problems, WTF."

If this was all done 6 months ago then going back to the shop will be a waist of time. But if it was like a few days back or last week then you might have a chance. Lets just hope the shop owners son did not take your car out for a "test" drive and blew your head gasket. This is why i always record my mileages when giving any car to a shop. Any smoke out of the exhaust? Any sweet smells?
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Old 09-09-2020, 08:28 PM   #16
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^^^^^^this

Shop worked on cooling system.....they need to fix
Period.
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Old 09-09-2020, 08:31 PM   #17
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IMO
It's a bubble
Now mind you I have 05, but one time
I had to park on inclined driveway, put front tires on ramps, ran can 20+ minutes while squeezing upper rad hose.
Finally did the trick
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Old 09-12-2020, 01:00 AM   #18
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https://i.imgur.com/hN0ZDuJ.png
^ pic of coolant temp plot from datalog, shaded blue area is freeway cruise


It's gotta be the thermostat. Running 205 on the freeway seems too hot. We might get another hot day to pull data, but everything about this seems like a thermostat that's not opening fully.

Last edited by 855T; 09-12-2020 at 01:48 AM.
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Old 09-12-2020, 02:34 PM   #19
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Quote:
Originally Posted by 855T View Post
Ran a quick log today...I saw 205 on the freeway but wasnít driving very long and itís close to 20 degrees cooler today. Iíll try and get a better log when it gets warmer.

Whatís a reasonable max? 210?
make sure you have enough water in system. I had a over heating problem due to that very problem, put some water in the system and it went away
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Old 05-25-2022, 01:53 AM   #20
855T
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Resurrecting this thread...


Had my first HPDE on Saturday at Willow Springs. I captured engine coolant temperature as part of my datalogging. For reference, air temp was mid 70s first session and low 80s by the fourth, and my intake temps ranged between 80 and 90 all day.



Peak coolant temperature reached 232 on my last session. I had the heater running most of the time and, when pushing, coolant temps were bouncing between 223 and 230 consistently. Warmup and cooldown laps saw more reasonable temperatures in the 215-220 range.



I'm thinking I need to go bigger with the radiator or consider an external oil cooler. I am hesitant to add new places for oil to leak, so I'm leaning towards the Koyo racing radiator and hoping that installation isn't an enormous pain. Anyone think an oil cooler is a better call?
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Old 05-25-2022, 02:13 AM   #21
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Becareful with hitting 230F things are starting to get hot in there.

I would first make sure there is no air in the coolant system by bleeding. You can buy no-spill bleeding kits and there are several tutorials online. If that doesn't fix the issue I would try to replace or inspect your thermostat. Check your radiator fans to see if both of them are working they should both kick on at 205F coolant temp. I had a bad radiator fan motor not work on the driver side and had to replace it which helped with temps drastically.

I've heard good things about the Koyo radiators and eventually plan to upgrade. Unless your radiator is cracked I don't think its necessary.

I have a 05 Sti on cobb stage 1 and I monitor temps pretty regularly. My coolant temps hover around 190-196F during hard driving however, mind you I do not track the car.
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Old 05-25-2022, 10:23 AM   #22
855T
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I can try burping the system again, but surely any air in the system would've found a way out after a year. The thermostat was replaced a year ago with an OEM Subaru part when this issue began - since then, it hasn't been hot enough outside for the issue to recur, so I figured that was the problem. And a radiator fan seems like it shouldn't matter at 90 mph on the track. At any rate, both fans are fine.

I'm still debating between a new rad and an oil cooler. I need to do something to take heat out of the system.
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Old 05-25-2022, 12:12 PM   #23
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have found heater core lines also trap air bubble...on my STI, a standard impreza and a 90 legacy...just disconnect the highest hose till water starts coming out and seemed to work it out for me
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Old 05-26-2022, 05:24 PM   #24
AliBenn
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i saw a program about some cars running Pikes Peak
car was over heating as you describe(not catastrophic OH mind you)
the car owner cut vent holes in the hood to let some of the hot engine compartment air to escape
it worked.
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Old 05-29-2022, 11:24 PM   #25
What could go wrong
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You may want to consider altering what you use for coolant as well if that hasn't been mentioned already... If you are using la strong anti freeze water mix your likely loosing out on cooling capacity if I remember correctly. A lot of people here in FL run just deionized water and water wetter, maybe a super weak antifreeze mix if you do trips up north or something... Worth a shot....

Likely burping the system thoroughly would be my bet but it looks like you may have done that already. I definitely wouldn't continue to drive it while overheating if you can avoid it...

Another thing to check: depending on who did your cooling overhaul, they may have used the wrong rad. WRXs have 2 radiator variants, an MT and an AT varient, and the AT had a chunk of the radiator carved out for a trans cooler. If your car is stick, and they managed to get an AT version working on your car somehow, that could also be an issue...

Last thing I'll mention is don't assume a new thermostat is a good thermostat, I had a new one from SOA be dialed in WAY to cold, the car would basically not get to operating temp. I swapped it out and it worked like a charm.
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