What is the best way to flush out coolant?

Tiny
IMTOOLER59
  • MEMBER
  • 2010 CHEVROLET AVEO
  • 1.6L
  • 4 CYL
  • AUTOMATIC
  • 82,000 MILES
I just bought this from a private owner that said it needed work. While checking it out I noticed he had added green antifreeze to the coolant tank, which I didn't catch before purchasing it. What is the best way to flush out the resulting sludge like material now in the cooling system?
Friday, January 17th, 2025 AT 4:00 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,520 POSTS
I would drain the coolant out the best you can, then fill the system with water from the garden hose and run it until hot, then drain the system again and repeat. Making sure none of the coolant enters the storm drains. Collect the coolant in buckets and then take them to the auto part store for recycling. Repeat until the fluid is clean then drain and add the correct coolant and top off with distilled water. Here is a guide to help you and I have included the drain for the system in the images below.

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

and

https://www.2carpros.com/articles/engine-coolant-59420607

It looks like you will need to drain the system by using the lower radiator hose, no drain plug :/ Check out the images (below). Let us know if you need anything else.

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Saturday, January 18th, 2025 AT 11:33 AM
Tiny
IMTOOLER59
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  • 27 POSTS
Good information, thank you!
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Sunday, January 19th, 2025 AT 9:52 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,520 POSTS
You are welcome, please use 2CarPros anytime we are here to help.
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Sunday, January 19th, 2025 AT 9:52 AM
Tiny
IMTOOLER59
  • MEMBER
  • 27 POSTS
I forgot to mention that they added the green antifreeze to the Dexcool already in the system, will clear water be enough to clean out the resulting sludge formed by the mixing of the two?
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Sunday, January 19th, 2025 AT 10:18 AM
Tiny
KEN L
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  • 50,520 POSTS
They do make a cooling system flush at the auto parts store, I would add that in after the first flush to relay help to clean it out.
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Monday, January 20th, 2025 AT 9:53 AM

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