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I'm going to have to disconnect one of the rear brake lines on my '66 to correct a problem with the parking brake. The person who did the restoration cannot recall what brake fluid type he put in. Is there a way to tell or am I into the drain/flush/refill routine?
If it's Dot 5 silicone fluid, it should be purple. If its Dot 3 or 4, it will be yellowish. Dot 3 & 4 are compatible with each other and mixing will not harm anything, but if there is Dot 4 in the system, mixing it with Dot 3 will lower the boiling point. Dot 5 can't be mixed with the other two.
Put some in a glass partially filled with water. DOT 3/4 will dissolve in the water, DOT 5 will sink to the bottom as a separate phase.
Although DOT 5 starts out as purple in the bottle, it turns to a yellow color in the brake calipers after use and heat. It should remain purple in the master cylinder, though.
Put some in a glass partially filled with water. DOT 3/4 will dissolve in the water, DOT 5 will sink to the bottom as a separate phase.
Although DOT 5 starts out as purple in the bottle, it turns to a yellow color in the brake calipers after use and heat. It should remain purple in the master cylinder, though.
Larry
I did this to determine what brake fluid the prior owner had used in my '65. It may have been Larry that gave me this trick and it worked great. Easy, peasy test.
Put some in a glass partially filled with water. DOT 3/4 will dissolve in the water, DOT 5 will sink to the bottom as a separate phase.
Although DOT 5 starts out as purple in the bottle, it turns to a yellow color in the brake calipers after use and heat. It should remain purple in the master cylinder, though.
Larry
Popped the cover off the master cylinder. Flashlight shows definitely purple fluid. However. drew some off with a syringe and found that the purple layer forms on top after shaking with water rather than sinking to the bottom as noted above.
I believe that Larry intended to say it floats rather than sinks. I'm concluding this is DOT 5 since from what I've found, the specific gravity of DOT 5 is 0.958, so it should float on water.
Popped the cover off the master cylinder. Flashlight shows definitely purple fluid. However. drew some off with a syringe and found that the purple layer forms on top after shaking with water rather than sinking to the bottom as noted above.
I believe that Larry intended to say it floats rather than sinks. I'm concluding this is DOT 5 since from what I've found, the specific gravity of DOT 5 is 0.958, so it should float on water.
Thanks for all the inputs.
You are correct...........I should of said "the DOT 5 fluid will form two separate layers in water rather than mix with the water like DOT 3/4".
That way I don't have to remember one which is lighter and which one is heavier.
10-10-2015, 01:47 PM
Any Way to ID Brake Fluid type?
