I somehow managed to get a hole in my rear brake line. I am trying to figure out where the hole is before I replace the line, in case it is rubbing on something that is not obvious. The master cylinder says DOT 5, so I assume that is what I am supposed to use, correct? I had read some stuff about changing it to DOT 4......Anyway, is there any way to tell what fluid is in there? I don't want to start another problem. Thanks in advance.

 

The DOT 5 fluid is technically better than DOT 4. It has higher dry & wet boiling points and is harmless to paint. Everybody still uses DOT 4, because DOT 5 doesn't play well with ABS brake systems.... SO don't feel bad about having DOT 5...

Here is an easy test to check what you have...

 

DOT 5. It's like SILICON OIl. Does not hurt the paint. Harley had to go to 3 or 4 when they went to ABS. Not all had ABS but they did not want the confusing. The last thing you want is something that will hurt paint hanging over your tank. Dot 5 is purple but it soon changes to straw and looks like 3 or 4. Just drop some in water if you do not trust what the person before you has done. DOT 5 will not mix and looks like oil in water. Dot 3 or 4 will mix with water. If it is 4, flush it all out good and use 5

 

Another fan of DOT 5 here, that DOT 4 is nasty stuff, sucks that ABS must use it.