Ok guys, problem and question

I bought the bike off a guy who does NOT know what he use for brake fluid. Brakes were fine last year but now rear is out. So I look in the master cylinder ........still full of fluid and it looks kind of yellow..........no puddles on the ground or squirting from lines or fittings......so I remove the brake plunger rod from the forward controls so I can push it by hand...........I here air as I push it in and out.......figure diaphram has pin hole......order rebuild kit from preformance machine .... So I'm not sure what fluid is in there ( yeah yeah put some on some paint blah blah)....Or can I just flush the whole system using a vacum pump and some brake parts cleaner ( CRC Brakleen ) that I put in a cup and suck it through the whole system to clean it out ............Then it would not matter what brake fluid I use dot 5 , dot 4 , dot 3........I would use dot 5.

Would doing this harm anything ? And would it work ?

I would like to know before I screw something up.

input wanted and needed...........

 

The original brake fluid in mine (87) was yellow and it was DOT 5. Yeah, I figured it should be blue... First time the cap had ever been off the rear (98,000miles) and still haven't removed the front.

I don't know exactly when they went from DOT3 to 4 or 5. But I was freaked seeing yellow and "reading" DOT5 on the cap. Used a vacuum only to get the bit of "cloudy" out of the mastercylinder. I figure that was moisture....

Just for reference - had a friend put DOT3 on top of 5. It turned to gel in 3 days and had NO BRAKES. He flushed (bled) it out with 5 and all has been well after 2 years.

 

Take a sample from the bike and a sample of dot 5 and put them together, you will be able to tell right away if they aren't the same as you can see they don't mix, DOT 5 turns yellow with age.

 

Just cleaned my rear brakes out. had been 10 years since I changed the pads and they finally wore out. I forgot what I used in the system. Flushed with denatured alcohol just like you described. Replaced with Dot 5 no problem since. Works good stops fine. Marked the cap with an engraver "DOT 5". Age and memory loss suck.

When Dot 5 ages it will turn yellow (amber).

Good luck. You shouldn't have any problem.

 

That's what I did and decided it was good to go. REALLY appreciate the tip about the color change - great information.

 

My bike takes DOT4 so I flush it every year. Get some speedbleeders and flushing will take 5 minutes per caliper.

 

sounds like a good plan, other than the brake parts cleaner. I would not run it through the system and I do not think it would need it either.

 

DO NOT MIX dot 4 and 5 brake fluids. The two fluids mixed will cause big problems and cost you big time. I do believe old Harleys used dot 5. I have a 2007 FXDL and it uses DOT 4. Check in the owners manuaul if you have one for your bike or check with a dealer.

 

really kind of funny, I have a 2006 that came with DOT5, guess I have an antique compared to a 2007. just drain the old and flush with some new. a little mixing during the flush will not hurt anything. just flush it all out.

 

what's that make my 48? I think harley went to Dot 5 in the 80s, not sure when they changed to Dot 4.