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Old 01-20-2025, 11:15 AM   #22
glennpm
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Join Date: Sep 2014
Location: Mid-Coast Maine
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Default Re: Under floor Master Cylinder Brake Bleeding

Quote:
Originally Posted by SoCalCoupe View Post
Poured some of what I bled out of the system into a deli container lid then poured some new DOT 3 fluid from the auto parts store into it. They did not mix, like oil and water. Then poured some water into it. The water mixed with the new DOT 3 but not the old stuff. Couldn't say that proves 100% the old stuff is DOT 5 but those would be the symptoms.
"Hydroscopic brake fluids are those that absorb moisture from the air, which includes DOT 3, DOT 4, and DOT 5.1. These fluids are glycol-ether based and can absorb moisture, leading to a gradual decrease in their boiling point over time. This characteristic makes them less suitable for vehicles that sit unused for long periods, as the absorbed moisture can cause corrosion and reduce performance. DOT 5 brake fluid, however, is silicone-based and is not hydroscopic, making it more suitable for vehicles that are stored for extended periods without use."

"DOT 5

DOT 5 is a silicone-based fluid and is separate from the series of DOT 2, 3, 4, 5.1. It is immiscible with water, and with other brake fluids, and must not be mixed with them. Systems can change fluid only after a complete system changeover, such as a total restoration."
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