Help... Brake Fluid
Melting Slicks
Joined: Jul 1999
Posts: 2,305
Likes: 1
From: Ontario, Canada
Are you asking what was originally in it?
or
How can you tell the difference between Dot 3 and Dot 5 (silicone)?
From the NCRS DB.
It's very easy to positively ID. Take a small, clear glass jar and siphon into it some of the fluid currently in the master cylinder. Then, add some DOT 3 or 4 glycol based fluid to the jar. Shake the jar and let it sit for several minutes, at least. If you see a "phase separation" (i.e. 2 distinct fluid "layers") in the jar, then the fluid in the master cylinder is DOT 5 silicone. If the fluids mix completely and there is no "phase separation", then the fluid in the master cylinder is either DOT 3 or DOT 4 glycol-based fluid.
An additional test that you could run is to take a small amount of the fluid out of the master cylinder and place it on a painted surface (a TEST surface and one that you don't care about). If, after a few minutes, the fluid mars or lifts the paint, then you know it's DOT 3 or 4 glycol fluid. If it doesn't affect the paint, at all, then it's DOT 5 silicone fluid.
Keep in mind that DOT 5 silicone fluid is dyed purple. However, the dye rather quickly changes color to yellow. Since regular DOT 3 or 4 fluid is USUALLY an amber-colored liquid, it's very hard to distinguish between them after the purple color changes. However, the DOT 5, even after it changes color to yellow, is still a much more pronounced yellow than the normal color of DOT 3 or 4.
Re: brake fluid ID
You can also use water. DOT 3 or 4 glycol based brake fluid is miscible with water. DOT 5 silicone is not.
DOT 3 and 4 has a distinctive odor. I don't recall that DOT 5 has much detectable odor.
or
How can you tell the difference between Dot 3 and Dot 5 (silicone)?
From the NCRS DB.
It's very easy to positively ID. Take a small, clear glass jar and siphon into it some of the fluid currently in the master cylinder. Then, add some DOT 3 or 4 glycol based fluid to the jar. Shake the jar and let it sit for several minutes, at least. If you see a "phase separation" (i.e. 2 distinct fluid "layers") in the jar, then the fluid in the master cylinder is DOT 5 silicone. If the fluids mix completely and there is no "phase separation", then the fluid in the master cylinder is either DOT 3 or DOT 4 glycol-based fluid.
An additional test that you could run is to take a small amount of the fluid out of the master cylinder and place it on a painted surface (a TEST surface and one that you don't care about). If, after a few minutes, the fluid mars or lifts the paint, then you know it's DOT 3 or 4 glycol fluid. If it doesn't affect the paint, at all, then it's DOT 5 silicone fluid.
Keep in mind that DOT 5 silicone fluid is dyed purple. However, the dye rather quickly changes color to yellow. Since regular DOT 3 or 4 fluid is USUALLY an amber-colored liquid, it's very hard to distinguish between them after the purple color changes. However, the DOT 5, even after it changes color to yellow, is still a much more pronounced yellow than the normal color of DOT 3 or 4.
Re: brake fluid ID
You can also use water. DOT 3 or 4 glycol based brake fluid is miscible with water. DOT 5 silicone is not.
DOT 3 and 4 has a distinctive odor. I don't recall that DOT 5 has much detectable odor.
with wyckd1