I currently have DOT 5 in my car. I would like to swap it back to DOT 3/4. I know the two don't mix well (like oil and water). What would be the best way to totally flush the old stuff out so I can get a clean start with the DOT 3/4. Any help would be appreciated.

get a suction deal to get all of the fluid out of the master, and refill with DOT3. then it's just a matter of bleeding the bejeesus out of the entire system- might need to flush a LOT of fluid thru it. a power bleeder would be a nice thing to have for this operation.
if you were really paranoid, i guess you could take all the lines loose and blow them out with air, then shoot some brake cleaner thru all the lines and wheel cylinders and what not, and just start over as iif it's a new system.

I have heard running rubbing alcohol will clean the lines, but I have never used that method myself.

Need to use denatured alcohol to flush out the DOT5. Even at that folks claim that the DOT5 can't be completely removed. I'd flush a couple of times, then fill and let sit, then drain and flush again. It would also be best to clean & rebuild the master cylinder, disk brake calipers and wheel cylinders (which ever the vehicle has). Then only the lines need to be flushed with denatured alcohol.

Rubbing alcohol has too much water in it.

Bob.

Need to use denatured alcohol to flush out the DOT5. Even at that folks claim that the DOT5 can't be completely removed. I'd flush a couple of times, then fill and let sit, then drain and flush again. It would also be best to clean & rebuild the master cylinder, disk brake calipers and wheel cylinders (which ever the vehicle has). Then only the lines need to be flushed with denatured alcohol.

Rubbing alcohol has too much water in it.

Bob.

That's it!

I knew it was some type of alcohol, thanks for the correction! :beers: