Can you refill engine coolant without flushing or draining?
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Joined: Aug 2016
Posts: 710
Likes: 74
From: SC
Over the years I have had more than one person say they had a vehicle that was overheating, they added coolant, and it was still overheating, only to finally figure out that they were adding to the overflow and not the radiator.
Of course if they keep filling the overflow and don't seriously overheat the motor it will eventually get into the system but just filling it up correctly is a much safer option.
Of course if they keep filling the overflow and don't seriously overheat the motor it will eventually get into the system but just filling it up correctly is a much safer option.
Your described scenario indicates that air has been captured in their system and not adequately removed (burped). Most likely, this happened by letting the overflow bottle run dry and when the system cooled down, it ingested air. This can also happen with head gasket failure, but that is much less common. You cannot get the air back out, once this happens, without burping the radiator.
The above being said, my initial reply was under an assumption that the OP had not ingested air into their system. As long as the radiator and block are air-free, topping off through the reservoir is perfectly acceptable and proper.
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Joined: Dec 2002
Posts: 1,043
Likes: 31
From: CA
I am late to this thread, would recommend you top off the overflow with distilled water and not coolant, specifically if it is noticed due to time and not due to settling or burping that happens just after a coolant change.
As shown and described, the overflow tube just hangs down into empty air. Over a heat cycle, some portion of GAS and vapor in the overflow is exchanged with the outside environment. Over a lot of cycles, the vapor exchanged ends up lowering the liquid level due to evaporation. But it is mostly water that has evaporated, majority of ethylene glycol does not evaporate (since ethylene glycol has a much higher boiling point and vapor point than water).
The liquid becomes more concentrated. it might even look a bit thick or grimey or even crusty. So adding Water and not coolant is the better course of action to bring things back to recommended original dilution, until you change your fluid more fully.
anyway, that's my 2cents
As shown and described, the overflow tube just hangs down into empty air. Over a heat cycle, some portion of GAS and vapor in the overflow is exchanged with the outside environment. Over a lot of cycles, the vapor exchanged ends up lowering the liquid level due to evaporation. But it is mostly water that has evaporated, majority of ethylene glycol does not evaporate (since ethylene glycol has a much higher boiling point and vapor point than water).
The liquid becomes more concentrated. it might even look a bit thick or grimey or even crusty. So adding Water and not coolant is the better course of action to bring things back to recommended original dilution, until you change your fluid more fully.
anyway, that's my 2cents
Last edited by raytseng; Oct 13, 2017 at 04:18 PM.
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nparthi
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