Hayes 9 bleed problems

John Flanagan

Hi all

I'm pretty savvy with mechanics but this has stumped me.... I cannot bleed Hayes 9 despite repeated attempts. I suspect the piston seals are bust as when I get to the stage of pumping the lever, all the fluid begins leaking from the piston. The bleed up to this stage is as expected - fluid going in, air bubbles clearing out - its the final stage which is failing.

Does anyone else have similar experiences? any pointers?

Cheers

John

The Rookie

Where does the fluid leak from the piston?

Noting that the piston holds no fluid, so do you mean cylinder or lever reservoir?

John Flanagan

Excuse the naming conventions - I mean the cylinder in the caliper. Pumping the brake as explained in the comprehensive instructions forced the piston out further than it should have been, causing the fluid to leak everywhere.

I have ordered a caliper rebuild kit, but I want to make sure this doesn't happen again. Any pointers?

The Rookie

Thats a somewhat different story to the first post!

The seals may be leaking air in, but normally they would leak fluid out as well and you'd see that.

What actually happens when you pull the lever?

mrmonkfinger

so you pumped the lever, and the calliper piston fell out?

did you still have the filler bottle attached to the calliper at this point? the pistons shouldn't move when you pump the lever, any fluid movement is taken up by the filler bottle.

John Flanagan

That's exactly it mrmonkfinger.... the calliper piston fell out. I still had the filler bottle and waste tubes attached.

mrmonkfinger

and the calliper bleed port was still open?

maybe there is something floating around and blocking the bleed port, so when you pump the lever, the fluid can't go out the bleed port into the bottle?

The Rookie

Surely with nothing holding the piston in place the fluid takes the line of least resistance, the bleed point is fairly restrictive so possibly just blew the piston out.

bikaholic

If the pistons have popped out and unseated from the caliper bores then you will have to unbolt the caliper halves in order to get them back in again. Take note not to damage the small o-ring that sits inbetween the two halves.

Question is, why was the brake bled without the pads in or a bleed block inserted to prevent this from happening?

In any case, you will need a vice or a small G-clamp to push the pistons into the bore holes. Be sure to protect the clamp contact points with card or tape.

Incidentally, the bleed procedure is best done using a syringe to pump fluid into the caliper end.

John Flanagan

Yep the piston blew out.... three times. I had assumed that there would be some mechanism of the piston being retained within the calliper - evidently not.

John Flanagan

bikaholic wrote:

Question is, why was the brake bled without the pads in or a bleed block inserted to prevent this from happening?

I was following Hayes instructions... there was no mention of keeping the pads in or using a bleed block.

I've ordered new pads too, so when I fit the new pistons, I'll be sure to use the old pads.

The Rookie

John Flanagan wrote:

I'm pretty savvy with mechanics but this has stumped me..

I'm starting to have my doubts......

John Flanagan

The Beginner wrote:

John Flanagan wrote:

I'm pretty savvy with mechanics but this has stumped me..

I'm starting to have my doubts......

Thanks for the support..... why do people feel the need to be negative? I have done countless repairs over the years for friends and family, and this is the first thing I have ever struggled with (first time on Hayes brakes). If you can't bring anything positive to the discussion then don't bother.

The Rookie

I'm not, I'm being a realist, the piston fell out, so you did the same thing again TWICE, for heavens sake, really, how daft was that - it really beggars my belief, I tried to help at ths start but as we go on it's clear you missed more and more out in your first post that was quite key in helping you.

If you were savvy, you'd not have done it the first time (logically there is no way of holding the pistons in) but then having done it once you persisted in doing twice more.....I try and learn from my mistakes (and yes I make them) not reinforce them!

I suspect the brakes would bleed just fine if you did it the way you are meant to.

Back to my earlier question what actually happens (happened) when you pulled the lever that made you suspect they needed bleeding?

John Flanagan

Thanks for the input.

As I said, I was following manufacturers instructions - hence the three attempts (I was convinced I was doing something wrong twice, but after the third attempt I realised that something had to be wrong). I knew they needed a bleed as the brake simply wasn't working, and while the pads need replacing, there was no more wear than the front which is working as expected. I didn't mean to sound ungrateful - I have had a long hard day and didn't like the tone of the comment.

Based on comments here, I have now completely disassembled the calliper and discovered that the little O ring is damaged. I will rebuild tomorrow when the kit arrives, and bleed as advised here with the old pads in.

Thanks again.

mrmonkfinger

The instructions for hayes brakes are a bit naff and they don't mention a block.

IIRC I just skipped the lever pump step when I bled my better half's Hayes brakes...

...or I might have popped the pads/disc back in. I can't remember, TBH. I don't recall the pistons falling out, though.

John Flanagan

Thanks for all your input. I managed to rebuild without the kit and they are now working as they should.

Cheers!