Poured washer fluid in the coolant reservoir?

Tiny
TRAVIS JG
  • MEMBER
  • 2010 BUICK LUCERNE
  • 3.9L
  • V6
  • 2WD
  • AUTOMATIC
  • 103,000 MILES
My friend accidentally poured washer fluid in the coolant reservoir. Was driven approximately 50miles since incident occurred and I was made aware. No problems with the vehicle except the washer fluid low warning illuminates and that’s when I realized what had happened. What are the best steps to take to remedy this problem?
Tuesday, January 20th, 2026 AT 4:01 PM

2 Replies

Tiny
STEVE W.
  • MECHANIC
  • 15,446 POSTS
Fill the washer fluid. Then it depends on when the cooling system was last serviced. If it hasn't been done in a while I would drain out the coolant and refill the system with fresh coolant. https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars
It would be due for a coolant replacement around this time anyway.
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Tuesday, January 20th, 2026 AT 4:58 PM
Tiny
KRAKENAUTO
  • MECHANIC
  • 81 POSTS
Washer fluid is mostly alcohol and water. However being they may also contain some detergents, I'd recommend flushing the cooling system.

It has likely already contaminated the entire system being driven 50 miles. Due to the chemicals and detergents in washer fluid I would highly recommend a flush since it could degrade rubber seals or cause corrosion to your cooling system.
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Tuesday, January 20th, 2026 AT 9:36 PM

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