brake bleeding

[rsjockey]

I have a '95 RS model with abs2. My bar-bak installation required fliping the top brake line and re-routing it. I have bled the system through both of the front calipers with a mighty vac pump but the brakes still seem a bit softer than when I started.

Is this a case of needing to bleed at the ABS nipples?

Any feedback?

[Ken H.]

Bleeding it at the ABS unit, might help, can't hurt.

[Phill]

I had to drain my front brake system replacing hoses and pipes on my 96 RT. I found that the system did hold some air too bled that abs tank but still found spongy. I then let it bleed by gravity first right caliper then other. Finaly got all air out.

[Willie]

One thing tha worked on my KLR after swapping out the front line was using a bungee cord to hold the lever in the squeezed position overnight. I had all the air out that I could see in the bleed line, but it still felt a bit spongy. A guy in the KLR forum told me to try this and it worked. Worth a try anyway. Terry

[Blue Beemer Dude]

I have bled the system through both of the front calipers with a mighty vac pump but the brakes still seem a bit softer than when I started.

 

I have never been satisfied with these vacuum bleeding systems. That's not how the fluid is supposed to go through the system, and I think it's the wrong approach.

 

Open the bleed screw, slowly pull the brake lever in until it's almost all the way down, then close the screw. Slowly release the lever. Repeat. After a few pumps, verify brake fluid level in reservoir. Do not squeeze quickly, or you may squirt fluid from the reservoir all over the bike.

 

You can also use Speedbleeders which makes it a little easier.

 

Do the same thing, but instead of bleeding from the calipers, bleed from the ABS pump.

 

Good luck!

 

Michael

[T__]

I have a '95 RS model with abs2. My bar-bak installation required fliping the top brake line and re-routing it. I have bled the system through both of the front calipers with a mighty vac pump but the brakes still seem a bit softer than when I started.

Is this a case of needing to bleed at the ABS nipples?

Any feedback?

 

rsjockey, you very easily could have introduced some air into your brake system & ABS unit when trying to bleed that hose area from a lower caliper bleed screw.. If the hose now goes up at the master cylinder or the banjo fitting is now upside down you could have some trapped air there also.. You also need the master cylinder level while bleeding or you could trap some air there also..

 

Brake bleeding kind of goes against nature you see.. Problem is: the heavier brake fluid wants to naturally go down & the air in the brake system naturally wants to go up or raise as it is suspended in the brake fluid..

 

If your brake lines & hoses went STRAIGHT up & down with no loops or high spots in the lines that were above the low spots in the lines it would bleed itself out through the take-up port in the master cylinder..

 

Problem is: If you can’t move enough fluid volume or move it far enough at one continuous time the fluid itself moves to the lower caliper bleed screws but the air runs back up the fluid filled lines & settles in the high spots in the lines, line connections, & ABS unit, etc.. Unless you can move lots of fluid volume quickly, the fluid trickles under the air trapped in the high spots or doesn’t move far enough at one time to flush out the bottom bleeder screws.. (that is why power or pressure bleeders are used on long run line ABS brake systems to bleed correctly)

 

The ideal way to bleed brakes is to back bleed by forcing fluid into the lower bleed screws & allowing the fluid & air to flush out the top into the master cylinder (very hard to do & can make a mess on the top of the bike)..

 

To add more complications to the bleeding process if you shake the brake fluid can, squirt fluid into the master cylinder with a small orifice type tool, or otherwise agitate it, it will aerate the fluid & as those thousands of little bubbles in the fluid reservoir travel through the brake system they combine & settle out in the line & fitting high spots as air pockets & that can & will leave a spongy brake pedal or brake lever..

 

I know it’s too late now but next time just bleed the top part (like that hose you removed).. If it was running pretty vertical all you would have needed to do was allow it to self bleed as you poured in fluid & watched the air bubbles escape out through the master cylinder take-up port hole, then after most of the bubbling stopped just pump the brake handle a few times & the air would have come out the top all by itself.. Or if the line made a few bends or flattened out, bleed it at the first bleeder screw below the hose (probably at the ABS unit)..

 

If you have air in the system now you will more than likely have to bleed it at all the bleeders in the side of the system you worked on.. Try to move as much fluid as fast as possible using the hand lever & working the bleed screws.. In a lot of cases once you have used the brakes a while it would have allowed the small air pockets to expand & contract so the possibility exists that they have combined at one high spot in the line or ABS unit & will bleed out as one slug of air.. Be careful not to aerate the brake fluid when pouring it in & if bleeding quickly cover the top of the master cylinder as fluid will want to squirt out the master cylinder take-up port hole & get on the bikes paint.. OH! by the way DOT 3 or DOT 4 brake fluid makes a great paint remover so be careful & cover all exposed painted areas..

 

Twisty