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Discussion Starter · #1 ·
2010 Outback. Would like to change coolant. In other vehicles I have drained cooling system, added distilled water, ran, then another drain and refill. Repeat multiple times until clean. I do not want to cause problems with head gasket leaks. Will I be OK over a week or two without the coolant system conditioner for my multiple drain, refill, and drive cycles? My owner's manual recommends the use of the Subaru Cooling System Conditioner when changing coolant. Thank you.

Scott
 

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2008 OB Limited 2.5i, Portland OR USA
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The lack of conditioner shouldn't be much of an issue for a short time.

The lack of coolant will be, though. Not a good idea to run straight water through, as a 50/50 coolant mix has a lubricant in it for the water pump bearings, it's the proper specific heat for thermal transfer in both the engine's water jacket and radiator, it's the proper boiling temperature, it provides freezing protection, and so on and so forth.
 

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Discussion Starter · #3 ·
Thanks for your response. I understand the water pump lubricant, better thermal heat transfer, freeze protection, as well as anti corrosion etc. I usually do this over a week's time in the summer. I am not a big fan of the chemical flushes, at least in some Fords have contributed to the timing chain cover leak. Also I had problems one time with a Ford Ranger that I had added the plastic flush adapter to a heater hose which failed. Some advocate an annual drain and refill, mine has factory fill from 2009 and 91,000 miles, so I would like to clean out the system. Does the Outback have a heater control valve which allows/restricts coolant flow to the heater core, or is the flow constant with a blend door?

Scott
 

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Does the Outback have a heater control valve which allows/restricts coolant flow to the heater core, or is the flow constant with a blend door?

Scott
Yes the Outback have airflaps that control air temperature by directing air through / around heater core.
The heater core flows hot continuously.
 
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I think I recently mentioned this in another thread - my lament about the blue coolant only coming pre-diluted. If you do what you describe in your original post, you'll have 100% water in your system from doing the flush. What would your strategy be to get back to 50/50 mix, given that you can only add 50/50 pre-diluted, and you can't drain all the water now sitting in your system? Sure, you can drain the overflow tank, drain the radiator, even pull a freeze plug on the engine and drain most of that. But you'll still have water sitting in the heater core and in various other cavities. So the moment you fill back up with 50/50 mix, you'll have instantly diluted it down to less than 50/50 due to the water residing in the system.

That's why I don't recommend flushing the system on engines where you can't get undiluted coolant. Instead I prefer to drain-and-fill more frequently than the suggested 102k miles or whatever it is the maintenance schedule calls for, to avoid creating gunk that needs to be flushed.
 

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^^ That is indeed a logical plan. One simply needs to decide on what drain-and-fill interval to select. For me, it is typically 60,000 miles. Regardless of what the manual says for ANY vehicle, the chemical agents and friction modifiers in fluids wear out substantially with enough time and heat cycles. Fresh fluid is always better than continuing to push degraded fluid, regardless of the particular flavor.
 

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Discussion Starter · #7 ·
Pep Boys has an undiluted blue coolant for about $15.00 per gallon. After multiple drive, drain, and refill with distilled water plan to add undiluted blue coolant to capacity. Then test with a antifreeze tester, adjust as needed. Unless you are Subaru fluid purists should be fine.

Scott
 

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I think I recently mentioned this in another thread - my lament about the blue coolant only coming pre-diluted. If you do what you describe in your original post, you'll have 100% water in your system from doing the flush. What would your strategy be to get back to 50/50 mix, given that you can only add 50/50 pre-diluted, and you can't drain all the water now sitting in your system? Sure, you can drain the overflow tank, drain the radiator, even pull a freeze plug on the engine and drain most of that. But you'll still have water sitting in the heater core and in various other cavities. So the moment you fill back up with 50/50 mix, you'll have instantly diluted it down to less than 50/50 due to the water residing in the system.

That's why I don't recommend flushing the system on engines where you can't get undiluted coolant. Instead I prefer to drain-and-fill more frequently than the suggested 102k miles or whatever it is the maintenance schedule calls for, to avoid creating gunk that needs to be flushed.
I do agree with you that it is important to minimize intermixing when doing final-fill to a cooling system.

Based on your comments above - I would like to make TWO points

1) The Asian-Blue is PREmixed because it is mixed with deionized water. (not distilled water like lesser antifreeze blends) It is not easy to find a source to purchase your own deionized water so they premix it. Any concoction which calls itself compatible with "asain blue" BETTER be premixed.

2) I have successfully used a LEAF BLOWER to remove most of the residual fluids after cleaning or rinsing a cooling-system. One has to consider that the thermostat will be closed when using this method to purge the final droplets. Just remove hoses and blow into them.... you might be surprised how much comes out the other end.
 

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Discussion Starter · #9 ·
Hey brucep,

Thanks for your input. I have had inorganic, organic, as well as biochemistry and was completely unaware of deionized water. Did a little research and it seems the price for the premixed is well worth it for the deionized water.

Scott
 

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I do agree with you that it is important to minimize intermixing when doing final-fill to a cooling system.

Based on your comments above - I would like to make TWO points

1) The Asian-Blue is PREmixed because it is mixed with deionized water. (not distilled water like lesser antifreeze blends) It is not easy to find a source to purchase your own deionized water so they premix it. Any concoction which calls itself compatible with "asain blue" BETTER be premixed.

2) I have successfully used a LEAF BLOWER to remove most of the residual fluids after cleaning or rinsing a cooling-system. One has to consider that the thermostat will be closed when using this method to purge the final droplets. Just remove hoses and blow into them.... you might be surprised how much comes out the other end.
DI or distilled is not a big deal. Used DI water for decades when processing semiconductors. Distilled should be the purest of the two but it depends on the post process handling.
 
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