Front Brake Bleeding, Once Again

Front Brake Bleeding, Once Again

Postby Z Grand » Sun Jan 09, 2011 3:58 pm

First of all, let me admit that I'm not the sharpest tool in the toolbox. I'm great at normal maintenance, as long as its not too technical. I've replaced clutches, adjusted valve clearances (though not on the CBX), changed brake pads, sprockets, chains, gaskets, bled brakes the old fashioned way with a small jar and a clear plastic hose -- that kind of stuff. But I have never rebuilt a caliper or replaced fork seals. And I didn't want the CBX to be my first try at it, since I know my limitations and didn't want to take a chance on doing any unnessary damage. So recently when the CBX had at least one front caliper and the rear caliper stuck, as well as a leaking fork seal, I decided to take it to a very reputable shop that does work on CBX's. They replaced all the fork seals, and rebuilt all three calipers. No biggie.

When it was time to pick the bike up, I towed the trailer two hours to the shop, but it had been raining and the shop has a fairly long dirt / gravel driveway. Normally I would go for a quick test ride, but I didn't want to take a chance dropping the old girl on the slick mud, so I loaded it on the trailer and headed home. When I got home, I took it for a test spin to make sure everything was working properly. Uh-oh, I've got a spongy front brake lever. The rear brake is fine. I called the shop and was told that they had spent an hour on the brakes with a vacuum bleeder and though they did not test ride the bike either, everything was fine when they were done. I'm wondering if there may have been some air hiding in the system somewhere and the jostling on the trailer on the trip home made it show up.

Since the shop is two hours away, I decided I would try to bleed the front brakes myself. I didn't want to go through the hassle of bench bleeding, and I don't have a vacuum bleeding system. I did some research on this site and others, and decided to try bleeding the front brakes with a syringe set-up very similar to the one below:

Image

I was able to get fluid to flow out of the system into the syringe and then force fluid back through the left front caliper to the master cylinder no problem. No air bubbles were evident in either direction. I then tried the right caliper. The fluid would flow out of the caliper into the syringe (squeezing the lever of course), again with no air bubbles evident, but for some reason I could not force the brake fluid back in the caliper, either with the brake lever depressed partially or fully out. Not really sure why, so I just buttoned everything up. I've still got what I consider to be a spongy lever -- the brakes will stop the bike fine, but the lever goes back to within maybe a half inch of the grip when you squeeze it hard. You can pump the lever a couple of times and it will get firmer, so I'm assuming there still may be some air in the system somewhere.

Currently I've got the bike on the sidestand with the wheel all the way to the left, and the front lever depressed maybe halfway with a cable tie. Over the course of the next day or so, I'll go tap all the lines (braided stainless ones) and the splitter several times with a screwdriver handle in the hopes that any remaining air will find it's way up to the master cylinder. Short of taking the bike back to the shop, any suggestions on what else I should try? Thanks in advance, and sorry for the long post.
User avatar
Z Grand
ICOA Member
ICOA Member
 
Posts: 366
Images: 2
Joined: Sun Jun 28, 2009 7:06 pm
Location: Walnut Grove, Georgia, USA

Re: Front Brake Bleeding, Once Again

Postby EMS » Sun Jan 09, 2011 7:15 pm

I think you have addressed the issue pretty well, Z! There was one other thing that someone had come up with: Connecting a vibrating device to the brake line and for the life of myself, I can't think of what it was anymore....maybe someone else remembers.
But you may be left with a slightly spongy lever anyway, because of "old" rubber brake lines :?: :?
Last edited by EMS on Mon Jan 10, 2011 8:35 am, edited 1 time in total.
To be understood is the exception
To be misunderstood is the rule.
User avatar
EMS
ICOA Member
ICOA Member
 
Posts: 9295
Images: 1702
Joined: Wed Mar 05, 2003 8:55 am
Location: North East OH, ICOA 3904

Re: Front Brake Bleeding, Once Again

Postby Z Grand » Sun Jan 09, 2011 7:21 pm

I remember reading about a vibrating device as well, but I don't really have anything suitable. The front lines are braided stainless steel ones that are about 5 years old and I had a firm lever before the rebuild, so I don't suspect the lines.
User avatar
Z Grand
ICOA Member
ICOA Member
 
Posts: 366
Images: 2
Joined: Sun Jun 28, 2009 7:06 pm
Location: Walnut Grove, Georgia, USA

Re: Front Brake Bleeding, Once Again

Postby Don » Sun Jan 09, 2011 7:37 pm

It is tough to get all the air out of the front system - I suspect the crossover fitting is probably the culprit

If you remove the bleeders and put a couple of wraps of teflon tape on the threads you'll have a much easier time - Part of the problem is that when you open the bleeder 1/4 turn or so to allow fluid to flow out, you've created a loose connection where air can also get in . . . . especially if you're reverse forcing fluid back up into the lines the way you are

Teflon tape and a Mighty-Vac or some other sort of pump system are probably necessary to get it ALL out

Don
User avatar
Don
Amazing Poster
Amazing Poster
 
Posts: 806
Images: 13
Joined: Wed Apr 02, 2003 4:13 pm
Location: Biloxi, Mississippi, USA

Re: Front Brake Bleeding, Once Again

Postby steve murdoch icoa #5322 » Sun Jan 09, 2011 8:52 pm

One of the other place that air can hide is in the master cylinder/reservoir.
Have you tried removing the brake lever and compressing the master cylinder with a punch when bleeding the brakes. The cylinder can travel another 1/4" or so than when using the lever and there MIGHT be some Don Ho tiny bubbles hiding. I think it was Mopar Tony told me about this method.
steve murdoch icoa #5322
ICOA Member
ICOA Member
 
Posts: 3165
Images: 19
Joined: Tue Mar 04, 2003 10:12 am
Location: St. Catharines, On. Canada

Re: Front Brake Bleeding, Once Again

Postby Z Grand » Sun Jan 09, 2011 9:27 pm

No, I didn't try that, but I did crack open the master cylinder banjo bolt with pressure on the lever in case any air was hiding there.
User avatar
Z Grand
ICOA Member
ICOA Member
 
Posts: 366
Images: 2
Joined: Sun Jun 28, 2009 7:06 pm
Location: Walnut Grove, Georgia, USA

Re: Front Brake Bleeding, Once Again

Postby Don » Sun Jan 09, 2011 9:41 pm

I think the brakes must be bled from the top down - All the air needs to be removed at the bottom, either by fluid gravity flowing downward (with the air bubbles) or being pumped out, downward. Loosening anything besides the bleeder on the caliper just gives you another place for new air to be introduced into the system

I sent you a PM

Don
User avatar
Don
Amazing Poster
Amazing Poster
 
Posts: 806
Images: 13
Joined: Wed Apr 02, 2003 4:13 pm
Location: Biloxi, Mississippi, USA

Re: Front Brake Bleeding, Once Again

Postby Z Grand » Mon Jan 10, 2011 7:32 pm

Well, the procedure seems to have worked. I have a much firmer lever tonight. Thanks everyone for your replies.

Don - I sent you a PM.
User avatar
Z Grand
ICOA Member
ICOA Member
 
Posts: 366
Images: 2
Joined: Sun Jun 28, 2009 7:06 pm
Location: Walnut Grove, Georgia, USA

Re: Front Brake Bleeding, Once Again

Postby t140d » Thu Aug 28, 2014 3:10 am

What was the single game changer of all the all the tips? Or is it best to cover all of points raised.
t140d
New Member & Happy To Be Here
New Member & Happy To Be Here
 
Posts: 1
Joined: Sun Mar 25, 2012 7:32 pm
Location: New Zealand

Re: Front Brake Bleeding, Once Again

Postby daves79x » Thu Aug 28, 2014 5:51 am

daves79x
ICOA Technical Director
ICOA Technical Director
 
Posts: 3416
Images: 0
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA

Re: Front Brake Bleeding, Once Again

Postby Z Grand » Fri Aug 29, 2014 8:39 pm

Yeah - I don't think it was any one thing -- probably a combination of everything. They've been operating well ever since. (Can't believe its been 3-1/2 years already!) Good luck with yours!
User avatar
Z Grand
ICOA Member
ICOA Member
 
Posts: 366
Images: 2
Joined: Sun Jun 28, 2009 7:06 pm
Location: Walnut Grove, Georgia, USA


Return to BRAKES: Calipers, Pads, Lines, Rotors, Upgrades & Fixes

Who is online

Users browsing this forum: No registered users and 1 guest