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Old 06-04-2020, 10:53 PM   #1
foxonwheels
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Question Overflowing coolant reservoir expansion tank

2013 WRX, 108k, Cobb stage 1

For the past few months, I've noticed my coolant expansion tank has been overflowing. I've done the burp procedure with a spill free funnel at the turbo tank a few times now. With all air out of the system, I did not experience any issues after taking a few short drives and staying out of boost. But boosting or going on a 40 min drive to and then from work caused the expansion tank level to be noticeably higher than where it started even after the engine cooled overnight.

Whenever it happens, there is obvious air in the upper rad hose when squeezing it once the engine cools down. Upper turbo coolant tank is also low. I have since replaced both the turbo tank and radiator caps with new OEM replacements. They are not reversed. My lines at the rad are connected properly. Both upper and lower rad hoses are hot when the engine is warm.

I did the timing belt, water pump, and t-stat (all OEM) a few months ago and replaced the coolant. There were some small rubber crumbs in the coolant and my upper/lower rad hoses felt a bit crunchy, so I replaced with silicone. Fans come on right at 205 and shut off around 192, new t-stat appears to be working fine.

I bought a pressure test kit and hooked up at the rad. Pumping up to around 13PSI and it holds, although drops maybe 1 PSI after 10 minutes. I also tested at the turbo tank and went up to 15PSI, again it very very slowly dropped to 13-14PSI. No obvious sprays, drips, or leaks that I could see.

No bubbles or foam in the expansion tank when revving. No signs whatsoever of milky coolant. My coolant tank does look a bit dirty inside near the top few inches where there normally is no coolant.

Tonight I reburped again and noticed something interesting. With the spill free funnel in the turbo tank with a decent amount of coolant in the funnel, I restarted the engine and revved a few times. No bubbles or excessive rise in the funnel. I then plugged the funnel, capped the turbo tank, and put the funnel on the radiator and removed the funnel plug. Revving now caused the coolant level in the funnel to immediately rise dramatically and stay there. Is this expected behavior or does it help diagnose?

With the funnel back in the upper tank, I notice that when I squeeze the upper rad hose a few times in succession, I can hear a water blooping noise somewhere under the intake manifold to the right of the turbo/upper coolant tank. Sounds like when a sink or a tub drains at the very end and you get a few 'glugs'. I'm guessing an air bubble is stuck and didn't work its way out. Does this mean anything?

Just trying to see if there is anything else I can try before I convince myself its a head gasket, which I was quoted at $3100 and will likely spell the end of my time with this car. I've done the burping procedure about 5 times by now over the past few months. Would a pinhole leak or bad hose clamp be able to cause such a dramatic rise in coolant in the expansion tank without showing signs of a leak? Clogged line or blocked passage somewhere? Do I bypass the TB coolant run? Replace the radiator? Don't want to throw more money at it if it certainly sounds like HG.
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Last edited by foxonwheels; 06-04-2020 at 11:00 PM. Reason: what about a blockage
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Old 06-05-2020, 06:22 AM   #2
mooshon
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I can tell just try this manual and make CO test.
https://strongforsubaru.com/resource...lant-bleeding/
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Old 06-05-2020, 11:11 AM   #3
Jedi03
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if you are bleeding it in full w/spill free i personally keep it in until the water starts to steam, i will often let it cool overnight if i have the time then plug and cap it...to make sure caps are not reversed you have the circle one on the radiator and the one on the upper reservoir is the oval one? if its backwards wont hold pressure properly at the radiator...also bleed it with heater running and after at operating temp give it a few revs, not to high but ~3k, i often will also hold it there to simulate a normal drive then let it idle down
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Old 06-06-2020, 10:17 AM   #4
Jay11STI
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I would try doing what Jedi03 has suggested first. I wouldnt want to condemn the headgaskets either until everything possible has been done.

Have you noticed any abnormal coolant consumption or loss? When you say "coolant overflow" are you saying that its litterally pouring out as in excessivly overflowing and spilling from the tank?

I only ask because in your first paragraph you said "I did not experience any issues after taking a few short drives and staying out of boost. But boosting or going on a 40 min drive to and then from work caused the expansion tank level to be noticeably higher than where it started even after the engine cooled overnight."

Coolant level will rise in the tank as it gets hotter due to thermal expansion so its not going to be at the same level in the tank after its hot compared to the level it was when the engine was cold after siting overnight.
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Old 06-06-2020, 11:46 AM   #5
Samurai Jack
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Sounds like you have been checking just about everything but also sounds like you still have air in the system. Could be from small leaks or could be you just never got all the air out of it.

Have you checked / re-checked all coolant / heater hose connections? Hoses compress over time under the clamps so definitely a good thing to check.

I have never used the funnel method you used to fill the cooling system. Many people have come to the forums with an issue similar to yours, have used the funnel method and have found air still in the system.

Suggest you try this method, which is how I always do it and never encounter your issues:
- motor off & cooled
- fill coolant overflow bottle to the fill cold line
- fill radiator allowing time for coolant to work it's way through the system pushing air out.
- cap radiator
- fill turbo expansion tank same as radiator
- start engine and let it idle. no revving needed. this works coolant throughout the system pushing air towards & out of the turbo expansion tank.
- fill expansion tank as needed
- after about 10 minutes, you can cap the expansion tank & check level of overflow bottle
- drive around for ~ 10 minutes & check overflow bottle. fill as necessary.

Never had an issue this method. I have never burped nor ever had a need to burp the system.

Now, since everything is already filled, I would suggest starting with a cold engine and remove the turbo expansion tank cap.

How low is the fluid level?
Start from here.
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Old 01-12-2021, 12:28 AM   #6
2ball
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was you overflowing issue a head gasket? If so how did you finally diagnose it?
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Old 01-12-2021, 03:45 AM   #7
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Make sure you have your funnel on the resivour not the radiator. And make sure your cap is not leaking. Coolant pressure sensors help a lot all cars should have them. Find that leak though that doesn't help any.
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Old 01-12-2021, 07:51 AM   #8
rtv900
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Quote:
Originally Posted by spoolinsti05 View Post
Coolant pressure sensors help a lot all cars should have them.
smh..
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Old 01-12-2021, 11:33 AM   #9
Jedi03
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don't know why i didn't put this in my last post, but have noticed Subaru's have a problem bleeding the air out of the heater core...i have pulled one hose while the vehicle is running to help get it out too...happened on 92 legacy 2.2 and a 99 impreza 2.0...not sure why, didn't have issues any time doing it on my STI but not to say it couldn't happen. I recommend do it while engine is cooler, i did it while hot, i do have a good pain tolerance but don't recommend doing this to anyone...220 degree or hotter coolant is no Bueno...
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Old 01-12-2021, 11:54 AM   #10
Max Capacity
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Quote:
Originally Posted by Jedi03 View Post
don't know why i didn't put this in my last post, but have noticed Subaru's have a problem bleeding the air out of the heater core...i have pulled one hose while the vehicle is running to help get it out too...happened on 92 legacy 2.2 and a 99 impreza 2.0...not sure why, didn't have issues any time doing it on my STI but not to say it couldn't happen. I recommend do it while engine is cooler, i did it while hot, i do have a good pain tolerance but don't recommend doing this to anyone...220 degree or hotter coolant is no Bueno...
May be jacking up the right front corner of the car as high as you can get it and turning on the heater to full heat while the engine is running, while your burping the system will help.

I do that.
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Old 01-15-2021, 01:12 AM   #11
spoolinsti05
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Quote:
Originally Posted by Max Capacity View Post
May be jacking up the right front corner of the car as high as you can get it and turning on the heater to full heat while the engine is running, while your burping the system will help.

I do that.

Thats what they recommend doing with the Nissan 240.

I drill a 1/8 hole in the thermostat.. Helps a lot!

Can even get those bleed valves for heater hose like on the jeeps Napa sells them..

Also you can get this a coolant vacuum refill kit theyre cheap and work great making it quick and easy to get the air out.
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Old 01-15-2021, 01:13 AM   #12
spoolinsti05
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Quote:
Originally Posted by rtv900 View Post
smh..
Yea sometimes I shake my own hand..
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