Brake fluid

[Dayron84]

I popped open the master cylinder and brake fluid is less than half full. According to TM it should be 1/8” from the top. Seems that it would over flow once lid is back on? Either way I need to top it off and not sure what fluid I’ve got. TM says to use dot 5 silicone fluid which I believe has a purple color. What I have is clear. Looks like regular dot 3 fluid. Any way to tell the difference?


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[glcaines]

DOT 3 and DOT 4 are miscible with water. DOT 5 is not. Take a small sample of what you have in your MC and add it to a cup of water. If it completely disappears, it is DOT 3 or 4. If it forms a definite separate layer, it is DOT 5 which is silicone based. As an aside, DOT 5 is only purple when new. With age it tends to turn clear or yellowish.

 

[Dayron84]

DOT 3 and DOT 4 are miscible with water. DOT 5 is not. Take a small sample of what you have in your MC and add it to a cup of water. If it completely disappears, it is DOT 3 or 4. If it forms a definite separate layer, it is DOT 5 which is silicone based. As an aside, DOT 5 is only purple when new. With age it tends to turn clear or yellowish.

Worked perfectly! Separated in the water so I’ve got dot 5. Thanks!


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[fasttruck]

The Army has ben sing DOT 5 in hydraulic braked vehicles for at least 25 years now.

 

[86humv]

CUCV's from 1984 uses Dot 5

 

[papakb]

Military gallons of DOT 5 silicon fluid look purple when it's in the container and anti-freeze yellow-green when poured.