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air in cooling system
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Old 09-07-2019, 11:17 AM   #1
bdobraj
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Default air in cooling system

Hello all,

I have an '05 Impreza rs wagon, with 360k miles.

A few weeks ago, I changed my timing belt and water pump with an AISIN kit. I attempted to drive the car to work a few days later, and within ten minutes of driving, the temp gauge creeped up to 3/4, and blew coolant out the overflow tank. The gauge only stayed at 3/4 for maybe a minute or so, and slowly lowered back down to the normal position.

At this point I believed that I didn't "burp" the coolant system well enough, and purchased a spill free funnel and tried that method. I let it run with funnel attached for about 30 minutes or so and watched air escape through the funnel. I was able to drive the car for approximately 800 miles before I encountered the same problem mentioned earlier.

I then replaced themostat and radiator cap with Subaru parts, "burped" the system the same way with a spill free funnel, let it run that way for about an hour that time. This time I was able to drive the car about 1200 miles before encountering the problem again. During this 1200 miles, I would check the coolant level often in the radiator and overflow tank, and would sometimes see bubbles in the overflow tank, still at the proper level, and other times, the overflow tank would be filled to nearly the top. I would check the levels usually after driving approx. 80 miles to work.

Throughout the 1200 miles, I did not have any issues with temp gauge, and it always read at the correct level. Each time I encountered my initial problem, it was always within the first 5-10 minutes of driving.

Today I decided to try the combustion gas tester, which remained blue and did not change the fluid to yellow, which leads me to believe that the head gaskets are good. I noticed that a clamp on I think the small hose coming of water pump (return hose?) was a little wet, so I snugged the clamp up some more. I wouldn't think that would be my issue though.

Aside from that little return hose, there are no visible leaks.

What is the next step?

Thanks all.
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Old 09-07-2019, 12:39 PM   #2
SoCoNoHa
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I'd start by replacing all those horrendous clamps that Subaru used on coolant hoses/lines with some proper hose clamps.

Also, I did a water pump for my buddy recently, and the new pump leaked from where it mounts to the block, right off the bat. Everything was clean and a fresh gasket was used, but it wouldn't seal. I even tried rtv but no go. Considering the old pump didn't leak, I'm guessing the mating surface of the new pump was junk.

Idk where aisin falls on the quality spectrum, but maybe try an OEM pump?
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Old 09-07-2019, 01:53 PM   #3
bdobraj
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Quote:
Originally Posted by SoCoNoHa View Post
I'd start by replacing all those horrendous clamps that Subaru used on coolant hoses/lines with some proper hose clamps.

Also, I did a water pump for my buddy recently, and the new pump leaked from where it mounts to the block, right off the bat. Everything was clean and a fresh gasket was used, but it wouldn't seal. I even tried rtv but no go. Considering the old pump didn't leak, I'm guessing the mating surface of the new pump was junk.

Idk where aisin falls on the quality spectrum, but maybe try an OEM pump?

Unless the water pump is only letting air in and not coolant out, it seems to have sealed okay, at least well enough to not leak coolant. The research I did indicated that Aisin brand is 2nd best to OEM.
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Old 09-12-2019, 12:41 PM   #4
BettyblueRS
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are you squeezing your upper and lower rad hoses while the no-spill funnel is on and the car is warming up? I've burped my system twice after my recent swap, the first time hoses weren't squeezed, second time I did and had more air coming out.
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