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2000 Forester S AWD
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Discussion Starter · #1 ·
Our Forester suffered from a bit of a frozen radiator yesterday :-( Only noticed this when the temp guage kept on going up - so pulled over before it got into the red and found there was no coolant in the overflow bottle at all. Waited until the engine colled down and limped the 1/2 mile to the Subaru rally garage where we had bought the car 6 months ago. To cut a long story short, the mechanic pulled the radiator out, defrosted it in front of a space heater and refitted it, then refilled with 50:50 antifreeze & water. It was taking ages to get the last litre or so of water in, and as the job had already taken three hours we agreed to take the car home and complete the job there.

Now comes the problem - we've been adding water gradually and running the engine. The system seems to pressurise ok, the heater works in the car (so probably no air bubbles in the system) and the temp gauge stays sitting in the normal position - so it would seem we do have coolant circulation. There is still a tiny drip we can't as yet locate but is hopefully from a hose connection and not a split in the raditor (it wasn't frozen solid). BUT - even if we run the engine until one of the fans comes on, no coolant appears in the overflow bottle.

How does coolant get into this bottle? How does it get back from the overflow bottle into the coolant system? The manual tells you to check the coolant level in this bottle, which we have been doing since we got the car and the level never changed until now. Is it possible that this part of our coolant system has never worked - and if so how do we check coolant level in the engine?

Your thoughts would be appreciated.

Thanks
 

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1998 Cayenne GTS 6speed
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1,751 Posts
Howstuffworks "How Car Cooling Systems Work"

You may have faulty/clogged radiator cap or hose, or you just do not have enough coolant in the system, which appears to be the case as you say you keep adding coolant (directly in the radiator, I presume); for the heater to stop working you need to have significant amount of air (~1L).
 

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2000 Impreza, 2003 Bugeye Sport, 2010 Base, 2014 Base, 2015 Premium, 2017 Limited, 2020 Touring
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1,020 Posts
Our Forester suffered from a bit of a frozen radiator yesterday :-( Only noticed this when the temp guage kept on going up - so pulled over before it got into the red and found there was no coolant in the overflow bottle at all. Waited until the engine colled down and limped the 1/2 mile to the Subaru rally garage where we had bought the car 6 months ago. To cut a long story short, the mechanic pulled the radiator out, defrosted it in front of a space heater and refitted it, then refilled with 50:50 antifreeze & water. It was taking ages to get the last litre or so of water in, and as the job had already taken three hours we agreed to take the car home and complete the job there.

Now comes the problem - we've been adding water gradually and running the engine. The system seems to pressurise ok, the heater works in the car (so probably no air bubbles in the system) and the temp gauge stays sitting in the normal position - so it would seem we do have coolant circulation. There is still a tiny drip we can't as yet locate but is hopefully from a hose connection and not a split in the raditor (it wasn't frozen solid). BUT - even if we run the engine until one of the fans comes on, no coolant appears in the overflow bottle.

How does coolant get into this bottle? How does it get back from the overflow bottle into the coolant system? The manual tells you to check the coolant level in this bottle, which we have been doing since we got the car and the level never changed until now. Is it possible that this part of our coolant system has never worked - and if so how do we check coolant level in the engine?

Your thoughts would be appreciated.

Thanks
I'd put some initial coolant in the bottle myself.

The sytem is a closed one, as the coolant heats and expands, it is supposed to go in the expansion tank, (incorrectly now commonly called an overflow tank). When the coolant cools off, it contracts, and the vacuum pulls the coolant back from the expansion tank into the system, hence a closed sytem with ideally no air in it. The system is pressurized to increase the boiling point of the coolant. You may alreay know that though.

You need to find and fix the leak though, because the system as it cools will pull in air as opposed to pulling the coolant back from the expansion tank.

Just another thought, do not Subbies have a radiator bleed screw somewhere near the top to bleed off air when refilling? I thought I saw this mentioned elsewhere.
 

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2000 Forester S AWD
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Discussion Starter · #4 ·
Thanks for everyone's coments and help. Sadly we have now found the cause of the problem - the radiator didn't survive the freezing as we'd first thought and the small leak was coming from a small and hard-to-find split in the radiator itself. We are now awaiting the delivery of a new radiator and will see what happens once we've fitted it.
 
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