I was told by the place that I use to rebuild master cylinders and boosters that mixing DOT 5 with regular brake fluid will cause the fluid to gel. They said that you must remove all traces of the standard fluid to keep this from happening.
E-booger says:
Tech Question
Gary Boak, Chilliwack, BC, Canada, 1969 Dart Swinger 340
I notice in the April 04 issue you say that DOT 5 brake fluid can be used without flushing the system. Everything I have heard and read states that Dot 5 does not mix with anything except DOT 5. When switching to DOT 5 are you not supposed to use new rubber?
Gary-
Another old wive's (or Mopar Muscle) tale. First, realize that DOT specs don't specify the composition of the fluid, the rating relates only to the boiling point. So, therefore, it would be possible to have DOT 3 fluid that's silicone, and DOT 5 that's not (and this latter combination does exist.) These specs are covered in detail in Federal Motor Vehicle Safety Standard section number 571.116, which is part of the Code of Federal Regulations, #49, Chapter V Subchapter S6.5.4 addresses miscibilty,
specifying that the fluid being tested must mix with a standard type fluid, and this miscibilty test DOES apply to DOT 5 fluids, and can't gel, swell cups, etc. when mixed. So there!"
