Having not owned my FLHTC very long adn not knowing the complete history, I decided to flush the brake fluid today and discovered that someone had previously used Dot 3 or 4 fluid instead of the recommended Dot. The fluid is clean and the brake work fine at this point. Should I flush the system and switch to Dot 5 or just stay with the Dot 4 fluid?

 

https://www.hdforums.com/forum/evo-c...l#post14576760

 

How do you know its 3 or 4?

5 loses it's purple color not long after use.

 

Well, i thought it was because the fluid was not purple but someone in the other thread told me that the Dot 5 fluid turns to a straw color after a year. Anyway, the fluid flush is done now. New Dot 5 and everything seems fine.

 

Good deal, I rather work with 5 anyday

 

I think in the long run your better off with DoT5. I was having rear brake issues. I would have to pump the brake the first stop. I bought rebuild kits for the MC and caliper, fully expecting them to be junk, as I had not changed the brake fluid, or even opened the top to look at it in 15 or 20 years. Hey, it's hard to get to, OK? When I took the caliper apart, it looked brand new inside with just a few marks from the piston wearing. No corrosion at all. MC was fine. The problem turned out to be a connection in the line. If that had been DoT3, the whole system would have been trashed from that abuse.

 

I didn't know the difference. Added 4 to my front m\s when I first got the bike 10 years ago. The gas from the master cylinder was leaking out the top and stripping the paint off my master cylinder. After about a year, I wasn't having problems but I thought I'd check the fluid. My whole brake system was filled with green jelly. Flushed the system with denatured alcohol and back to 5. They don't mix weel!

 

Yeah, Color isn't a reliable indicator. If you put some between your thumb and forefinger and put pressure on while trying to rub your fingers together. Dot 5 will feel slick. The others won't.

 

In a another thread just posted yesterday i believe i stated the difference. one is silicon base and the other is glycol-based that's why you can't mix 4 & 5. the following link has some good information that all of us could read. Silicon based fluid is better for the seals in the system over the glycol based....

http://www.epicbleedsolutions.com/re...1-brake-fluid/

 

Isn't DOT 5 silicone based or something? I am drawing from old memory here.