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2009 Forester XT
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122 Posts
Discussion Starter · #1 ·
So we just replaced the radiator in our '02 forester yesterday. The top tank's seal gave out on the old one & was spraying all over the motor. So, I went ahead & installed the new one, poured a new gallon of subaru coolant in, along with about a quart of distilled water. Admittedly, we were in a hurry and I completely skipped the "burping" step. Today we drove the car a total of about 500 miles (moving out of Texas, it's a big state). Every time we stopped, I would check under the hood & a bunch of coolant seems to be spraying from the radiator cap, all over the intake ducting. We watched the temp. gauge like a hawk all day & it didn't go beyond normal operating temp at all.

So, my theory is that because I didn't burp the system, air is caught near the thermostat & it isn't opening in tome to prevent the cap from spraying. Thoughts?

Also, I just replaced the head gaskets / water pump / thermostat / radiator cap a couple months ago so those should all be pretty solid.

Thanks!
 

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2007 Forester SportsXT AT
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1,613 Posts
You may have overfilled it, i may be wrong but my observation is that there needs to be some room in there for when the thermostat opens and closes and if it's over filled then the pressure is going to build and release through the cap. I feel like you should be able to let the cap do it's thing until things return to normal and enough excess fluid will be released and it will stop spraying.
 

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2003 SG Manual
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30 Posts
If there is any 'excess' coolant in the system, it'll bypass the cap n disappear into the bypass bottle. Make SURE you bleed the system of air, then recheck. Might just be as small as the cap not being done up correctly.
 

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1999 L 4AT
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1,222 Posts
Also, I just replaced the head gaskets / water pump / thermostat / radiator cap a couple months ago so those should all be pretty solid.

Thanks!
Ideally, with a new radiator a new cap is recommended because the seal on the old cap has formed to the opening of the old radiator. You might be able to get away with the old cap by re-seating (open and close) it a few times until the seal finds a sweet spot.
 

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2017 Subaru Forester XT CVT
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10 Posts
Spring for a new cap. You already spent a bunch on the motor, don't skimp or chance an overheat. Fill the overflow bottle with coolant. As the engine runs the air will eventually come to the top of the radiator. As the motor cools it will draw coolant from the recovery tank and displace the air in the radiator. This may take a day or two depending on use.
 

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2009 Forester XT
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122 Posts
Discussion Starter · #6 ·
Thanks so much for all the prompt replies, everyone! I picked up a new NAPA cap this morning, as we're out in the sticks & nowhere near a Subaru dealership & will replace it with a Subie cap asap. I've honestly never heard of a cooling system being overfilled, though. I've always just topped off the radiator with the car running 'till I feel that all the air is out, full the overflow to max & call it a day with no issues. Could someone elaborate on the whole overfilling thing?
 

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2007 Forester SportsXT AT
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1,613 Posts
well, when I burped the system, and stuck a funnel in the radiator hole, and turned the motor on and ran it for awhile and squeezed the upper radiator hose to get any stubborn air bubbles out, the coolant would periodically rise and lower in the funnel to the point of overflowing a little, I'm assume due to the thermostat opening and closing, and say if you shut the motor off during a "lower" point and then filled the radiator completely full and put the cap on then it would be overfull and the pressure would build when the motor is turned on again and the thermostat opens with the cap on and the excess fluid would escape through the cap.
 

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2009 Forester XT
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122 Posts
Discussion Starter · #8 ·
Good news! It appears to have been the cap! Even with the cheapie NAPA cap, it hasn't sprayed a drop! Thanks everyone!
 

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2019 Crosstrek 2018 Forester XT
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Silence2-38554;3165785 Could someone elaborate on the whole overfilling thing?[/QUOTE said:
Almost every vehicle I have had...I fill the radiator all the way up..drive it a few miles. Let it cool and then refill the radiator. PIA but it always works. Need to do it maybe 3 times.
 
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