[al-irl]

I'm having a bit of trouble bleeding a front hayes dh-mag. I reckon there is air stuck in behind one of the pistons. It doesn't want to go anywhere. I've tried bleeding it from both lever and caliper, Ive tried sucking the new oil in through the lever and back out through the caliper using a syringe. I was kind of getting somwhere after bleeding the brake about 6 times i was getting a little feel at the lever. It was starting to pump up a bit but not of much use. So i decided to start from scratch and split the caliper and reset the piston hoping i would force any air trapped behind the piston out. I thought it was going to work when i reset the first piston and oil came out through the little hole. When i reset the second one nothing came out. So i thought to myself that i had got it. I reasembeled the caliper and then bled the brake and i was back to square one. The lever was again pulling back to the bar.

Has anyone got any tips for getting the air out from behind the pistons. Or am i stuck with bleeding this brake about 50 times till all the air is gone.

Help me before i go mad.

AL

 

[buildyourown]

For starters, your going the wrong way. Pump the fluid from the caliper to the lever. No sucking!
I think you can download instructions from the hayes site.
Here's how I do it: Put a hose on the lever site. Run that hose into a bottle with a little bit of fresh fluid.
Put second bottle with hose on caliper. Some like the syringe, I prefer the bottle. Squeeze for 5 sec, release for 3. Repeat that pulse about 10 times until you aren't getting any bubbles back. Then just squeeze like hell until you got clear fluid coming out the lever.

 

[MikeD]

For starters, your going the wrong way. Pump the fluid from the caliper to the lever. No sucking!

I disagree...I was totally frustrated by syring-bleeding Hayes until I was shown that sucking some fluid back with they syringe would dislodge some otherwise immobile air bubbles in the caliper. I don't finish the bleed this way...I first push fluid through (until the outflow hose has no air in it), then suck some back in from the outflow bottle, then push through again until it's all new fluid inside. Works like a charm every time.

As to why you have air in there, al, I can't guess...I'd try rotating the caliper around as I bled it, tapping it with a wrench, trying to get that air out, if that's indeed your problem (and it's not a stuck/stubborn piston or anything...) Wish I could give some more insight.

MD

 

[buildyourown]

I disagree...I was totally frustrated by syring-bleeding Hayes until I was shown that sucking some fluid back with they syringe would dislodge some otherwise immobile air bubbles in the caliper. I don't finish the bleed this way...I first push fluid through (until the outflow hose has no air in it), then suck some back in from the outflow bottle, then push through again until it's all new fluid inside. Works like a charm every time.


MD

Read my whole post. Al's post sounded like he was trying to complete the whole bleed by sucking. The !!! was a joke.

Another thing I just remembered. Make sure the caliper is rotated so the bleed fitting is pointing up. Usually you can just remove one adapter bolt and rotate it. I've found bubbles this way.

 

[al-irl]

I tried doing it the way you suggest originally. First with the hayes squeesy bottle. Attached at the caliper forcing the old fluid back out through the lever. I didn't have any great luck. I then moved on to the syringe (my prefared method always use it when im doing shimano, hope etc) Still no joy.
The reason i tried sucking the fliud was i reckoned i might be abel to suck the air out along with the fluid. I set up bottle of oil with a tube connecting to the lever and then sucked from the caliper using the syringe. All i got was a syringe full of oil and no air bubbles.

I seem to just be getting the oil to flow through the caliper and very little air seems to be comming out if any each time i bleed it. No matter what method i've tried. I've tried tapping the caliper, hose and lever with a screwdriver handle and every trick i can think of to get the air to move. But to no avail.

thought someone here might have had the problem b4 and found someway of solving it. Cheers for the advice so far but i've been there done that.
AL

 

[RideMTN]

If you are doing everything correctly(Turning the wheel so the brake lever is at an elevated position, and then push the fluid from the caliper to the lever body) then it seems like there is a bigger problem. It could be a few things. 1-One of the compresion fittings is bad. Some times they just crack and oil and air are free to move in or out.
2-Master Cylinder is bad. Brakes take a lot of abuse, sometimes you can get a pin sized hole in your MC and all it does is just suck in air.

I was have the same kind of problem you are haveing with my hayes brakes. It didn't matter how many times I would bleed them the lever was still soft. Through process of elimanation I found the problem.

I hope this is of some help to you.
Thanks,
Justin

 

[Dartman]

Flick the lever a few times while everything is open to shock loose bubbles in the system.

 

[bullcrew]

It must be bad, I'll buy it for $15.
It can never be fixed, get it off there before you hurt yourself, OOOO OOUUCH!
I'll give ya $10.