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2005.5 overheating after 15 minutes


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So I flushed the system like 3 times in a row but I think I still have air in the lines somewhere. 15 minutes into driving my car heats about 20 deg higher than it should. I also installed a 146 tstat and used Subaru coolant and the additive and followed flushing procedures but maybe I'm missing something.:spin:
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Check out for a bad head gasket. Or even worse - warped/cracked head.

 

Compression, mist/funny smell at exhaust, water in oil, oil in water...

 

But do you read the sensor value or is it just the needle in the instrument cluster that's poking around? It may of course be a faulty sensor.

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I don't get any codes and the only reason why I flushed the system was to replace with a cooler tstat. I never replaced any of the hoses but I don't have any leaks. I did a pressure test and it nada. I followed the Subaru manual by the numbers 9-10 steps and repeated it like 5 times but once I get her on the highway, blah, 15+ minutes later extra hot coolant is backed up into the overflow and pops the top open. I really don't want to go to the dealer and blow $100 on a flush because I'm not doing right...

 

I don't have any oil in the water, funny smell, compression issues or otherwise, just hot than normal coolant getting rejected from the turbo reservoir back into the overflow...then after a few runs I lose about a Qt or so and have to refill routinely.

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Mine didn't have an overheating problem, but I did have the overflow boiling over. When the mechanic did a pressure test, we watched the top radiator hose ballooned up an extra half inch in diameter.

 

I also did the TSB with the radiator caps, replaced both and cut the overflow hose shorter.

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Mine didn't have an overheating problem, but I did have the overflow boiling over. When the mechanic did a pressure test, we watched the top radiator hose ballooned up an extra half inch in diameter.

 

I also did the TSB with the radiator caps, replaced both and cut the overflow hose shorter.

 

what was your issue, clogged radiator/lower rad hose?

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The pressure test showed a slight pressure loss partly due to the upper radiator hose. Mechanic also noticed some dry coolant so he ended up replacing the radiator as well along with the thermostat. Also ran a pressure overnight just to make sure it wasn't a head gasket issue. Haven't had a problem since.
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Try running the heater on full blast a few times whilst letting the car warm up with the radiator cap off. This will get out any air trapped in the heater core as well.

 

I think the bubble is in the heater core too. Park the car on a ramp or uphill , put the heat on blast and use a coolant funnel to displace the air with coolant as it flows through the radiator.

 

Also as the car is warming up, place your hand on various coolant hoses (use caution, don't lose your hand or arm!) or IR thermometer to see if they are getting warm as well.

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Another issue that can cause overheating is if the water pump is bad. The impeller may be loose on the shaft or something similar.

 

And also check that the radiator cap is in good order and that you have the right cap. Wrong cap would give the wrong pressure.

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I found some confiming details (similar to what ehsnils said) with regards to the radiator and turbo reservoir caps and the hose in the overflow. Too bad this isn't a recall so I can try to scam a fresh block out of the deal.

 

http://www.import-car.com/Article/63198/Subaru_Coo.aspx

 

Tech Topics

 

Subaru: Coolant Comes Out of Reservoir

 

 

September 02, 2009

 

 

If you encounter a vehicle that experiences coolant coming out of the coolant reservoir tank, it may be caused by the radiator cap pressure valve being stuck open by debris sucked up through the reservoir tank hose.

 

 

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If you encounter a vehicle that experiences coolant coming out of the coolant reservoir tank, it may be caused by the radiator cap pressure valve being stuck open by debris sucked up through the reservoir tank hose. As the cooling system cools down, it sucks coolant back into the radiator.

If there is debris that settles to the bottom of the reservoir tank, the hose is low enough to also suck debris back into radiator. This causes the radiator cap not to seal, allowing excessive amount of coolant to escape overflowing the reservoir tank. If this condition continues over time, there will not be enough coolant in the system to maintain proper engine temperature.

 

In order to correct the condition you need to clean (and test) or replace the radiator cap, clean out the reservoir tank, and slightly shorten the hose, following the below repair procedure.

 

 

 

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Looks like replacing both caps and actually having them in the correct locations(137kpa for the turbo reservoir) corrected the problem. I additionally found out from a Subaru mechanic that when you swap out your tstat for a lower temp tstat, the pressure that normally is generated won't be enough to open the stock caps to allow antifreez back into the radiator, thus the back flush into the overflow tank. I also trimmed the hose that runs down into the overflow tank back by about 3/4". The stock length was jammed all the way to the bottom causing it to suck the very bottom of the tank and pulling any crap up into the cap and causing needle operation issues.

 

I flushed it twice with some prestone radiator flush, allowed the engine to heat up, fan to turn on and then shut it down, allowing it to cool for about 40 minutes and then after filling with the Subaru coolant (following the same procuedure) it was fine.

 

The Subaru mechanic also told me NOT to use the Subaru additive that many dealers tell you to use. He said unless you have leaks in your radiator or other leak related issues DON'T use it! It has ginger root and other components in it the swell up when exposed to hot heat, thus f*cking up the needle valves in the two caps.

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  • 4 weeks later...
Looks like replacing both caps and actually having them in the correct locations(137kpa for the turbo reservoir) corrected the problem. I additionally found out from a Subaru mechanic that when you swap out your tstat for a lower temp tstat, the pressure that normally is generated won't be enough to open the stock caps to allow antifreez back into the radiator, thus the back flush into the overflow tank. I also trimmed the hose that runs down into the overflow tank back by about 3/4". The stock length was jammed all the way to the bottom causing it to suck the very bottom of the tank and pulling any crap up into the cap and causing needle operation issues.

 

I flushed it twice with some prestone radiator flush, allowed the engine to heat up, fan to turn on and then shut it down, allowing it to cool for about 40 minutes and then after filling with the Subaru coolant (following the same procuedure) it was fine.

 

The Subaru mechanic also told me NOT to use the Subaru additive that many dealers tell you to use. He said unless you have leaks in your radiator or other leak related issues DON'T use it! It has ginger root and other components in it the swell up when exposed to hot heat, thus f*cking up the needle valves in the two caps.

 

 

If i'm not mistaken, the turbo res is 108kpa and the main is 137kpa? did you put a 137 on the turbo res, and was that what solved your problem? meaning the 137 is better than the 108 on the turbo res? or perhaps you just made a mistake. i only ask this because i'm having similar problems, i just had my car flushed, tstat replaced, and my coolant does not appear to have oil in it, and i have no other signs of head gasket failure aside from my cars temp going to abouuuut just below the red, then back to half, then up to 3/4s, back down to half....and i still have a gurguling/trickeling water sound from the dash, and when i stop the car, my res is boiling over. i'm praying its just the cap that fixes this issue. if not, than next stop the radiator, and final stop....head gasket :mad:

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  • 1 year later...

Bump to correct misinformation in this thread;

 

Filler Tank cap= 108kpa (16psi) -- part 45137AE00B (standard replacement at any parts store)

Radiator cap = 137kpa (20psi) -- part 45137FE002 (cannot find an aftermarket equivalent)

 

-Rob

 

legacygt_rad_cap_test.jpg

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