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2003 Front Brake Issues

1K views 8 replies 5 participants last post by  Arjay67 
#1 · (Edited)
I'm helping a friend who purchased an '03 RR and we are having some trouble with the front brakes. The lever is loosing pressure, but it's completely random when it happens. You can get a firm lever, roll the bike around the garage a little, pull the lever again and it will be flat. It doesn't do it all the time. It doesn't go flat overnight like the master was leaking. It's just completely random when it happens. It can go from flat to firm to flat to firm in the matter of a minute or two.


What we have done so far:



  • We started by just simply bleeding the system. Same problem.
  • Rebuilt the Master Cylinder with OEM kit, replaced lines with Galfer SS lines, & bled the system. Same problem.
  • Bought a MightyVac bleeder to ensure all air was out of the lines to bleed the system again.
When we went to bleed the system with the MightyVac, while working on the front right caliper building vacuum, it started pulling air and a little fluid out of the bleeder valve BEFORE I had even cracked it open. Thought this might have been the issue, so we swapped bleeder valves and the same thing happened. Left caliper is fine.


At this point I don't know if the seal of the bleeder valve is bad somehow and allowing air back in the system, or if it might be something like a piston sticking.


Right now we are looking at replacing/ rebuilding the calipers, or moving back to look at the master cylinder again. When rebuilding the master, the piston had a nice feel and was a simple rebuild.


Any ideas or help would be appreciated!


Also if anyone does have some 03-04 calipers for sale we might be looking!


Thanks!
 
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#2 ·
  • We started by just simply bleeding the system. Same problem.
  • Rebuilt the Master Cylinder with OEM kit, replaced lines with Galfer SS lines, & bled the system. Same problem.
  • Bought a MightyVac bleeder to ensure all air was out of the lines to bleed the system again.
Thanks!
If you want to isolate the nipple, take em out, wrap some teflon around the thread and try again.

When you replaced the lines (to Galfers) did you replace all the copper washers and bolts? (just in case)

Make a visual inspection of the calipers (all around) looking for small cracks...

Silly question... have you seen any leaks?

You can always remove the whole front braking system (MC+lines+calipers) from the bike and carry more test easier...
 
#3 ·
We thought about trying the tape, but the bleeder is basically a needle valve which if it isn't seating correctly won't leak out of the threads, but out of the actual port. Correct? It's not leaking from around the threads, but out of the bleeder nipple.

We did replace all the banjo bolts and all crush washers with the new lines, (uppers and lowers) and torqued to spec.

No visible leaks anywhere in the system before we even tore into things originally.
 
#4 ·
yes. if it's not seating it will leak out the port.

however, the threads don't seal for obvious reasons, so when you use a vacuum pump you will pull air through the threads and out the port. I hate vac pumps for this reason, it's near impossible to know that you aren't drawing air through the threads instead of from the system
 
#5 ·
Update:

Installed completely rebuilt calipers on both sides. New pistons, seals, bolts, bleeders, everything. Refilled and bled the system and got the exact same issue. This is beyond baffling and frustrating now!

The master cylinder is the only piece left that isn't completely 100% new. We did rebuild it with an OEM rebuild kit. My only thought is that the seals were not put on correctly by the previous mechanic possibly. I put the new ones on the same way the old ones came off. The previous owner said that he had the local Honda shop rebuild the system and it was "never quite right" after that.

So, can anyone tell me which way they are supposed to go? I can not find any rebuild information online that shows this much detail.

The picture below is how I put them back on originally, also the way they came off. The taper of the seals angled towards the piston and away from the spring.



OR

Should the taper angle towards the spring and away from the piston? I've taken the master apart and swapped them to take the photo. I'll await some suggestions before reinstalling this way to test the system.




OR does it not matter at all?

Any thoughts? I'm running out of things to check. Thanks everyone!
 
#7 ·
After doing some research today I've found from the service manual that the gaskets appear to taper towards the piston. This is the way that we had them originally which still led to our issue.

However, I did see in the diagram that the spring guide and spring were installed backwards. According to the diagram the spring guide is mounted facing the piston and not the MC. I had it installed opposite because that is the way it came out before the rebuild.

My plan is to reverse that this evening and see if that might be the cause of the soft lever.

 
#8 ·
I just did my calipers and pads and seem to have the same issue. I say seem because I just completed them this morning and haven't had much time to look at them. Couple of thoughts I was having/noticing....

With the steering all the way to the left the master is still sitting relatively level. This makes it really hard to get air out. On a different Honda that I have, when the bars are full left the angle of the master is such that air will naturally raise up and out of the system. This can be seen (on that bike) when you rapidly and repeatedly hit the front brake lever. On that bike I just hit the lever repeatedly until no air is visible in the master. On this bike, full left seems to still leave the master level which may mean I have to bleed it the old fashioned way (crack the line to the master).

Also, just as a general FYI, it's never a good idea to full stroke the master when it's gone some miles on it and hasn't been rebuilt. What can happen is that you get a wear ridge in the master at the end of the piston's maximum travel point. So if it's got a 'wear ridge' and you full stroke it you push the cup seal over the ridge and it can damage the cup.

I'm just spitballing - perhaps some of it may help. I might be in the same boat though, will know more after lunch :)
 
#9 · (Edited)
After a bit of a brake (haha) I looked at it again this morning. I tried to bleed the master through cracking the banjo bolt but this was a bust and introduced more air into the system. I then took the master off (two 8mm bolts with the bracket being directional) and this enabled me to put it on an angle where the air would naturally travel up and out of the master. I tied off the brake lever (leaving the master cracked open so the air can flow through) and I'm pretty sure this will case the issue for me.

Good luck with your repair - methinks you're fighting air 0:) BTW, with regards to the piston seal, think about how it operates. As you pull on the lever it pushes the piston in. The brakes are activated by increased oil/hydraulic pressure. The piston slides in a tube and the piston has to seal in that tube to increase the pressure. If you consider how it works it becomes clearer which way the piston seal needs to be oriented to create the best seal when under pressure...
 
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