One item you really cannot test for is brake fluid grit or dirt contamination. This caliper piston has wear marks on it where it contacted the square cut caliper body seal.
If you put your finger into the fluid in this caliper body and rubbed it against your thumb, you would feel grit. The problem was that when a new caliper was installed the old fluid which was contaminated with grit was not serviced or flushed. The old fluid was then forced into a new clean caliper causing this abrasive wear.
Another item to always be aware of is petroleum contamination. Whenever you remove a master cylinder cover of the style shown look at it for any rubber gasket distortion.
If the rubber gasket is “puckered” as shown in the two examples shown it indicates petroleum contamination of some type. It could be power steering fluid, transmission fluid or a myriad of other fluids.
If you find such a condition suck out the fluid in the master cylinder and place it in a clear jar or empty water bottle. Let it sit and the petroleum contamination will separate from the remaining brake fluid. This is not the only test for petroleum but it is a quick and easy initial test.
Another simple test for petroleum contaminated fluid is to put it in a Styrofoam cup.
Petroleum contaminated fluid will generally eat through the Styrofoam cup at the fluid level line. This test will not work on cups with any degree of plastic mixed into their makeup.
Remember the most important thing to do is to test brake fluid on a regular basis and test more often when the copper content reading is 100-200. Failure to service brake fluid when required can lead to serious and expensive brake problems.
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