SRAM/Hope hydraulic brake, bleeding issues

[chriswoody]

So I'm trying to get my new Hope calipers fitted and bled and I'm having a right mare.

So with Dot 5 systems, you need to first run fluid through the system from the caliper syringe to the lever syringe. The fluid does goes through, but there is a bit more resistance than you would expect. Then you are meant to secure the lever back against the bar to isolate the caliper, before bleeding that. Then comes the part that I'm flummoxed by, you need to release the clamp on the lever and then gently let it return as you push in the plunger in on the caliper syringe. Now I've done this on the front brake in the past with no issues, but on the rear, nothing. The plunger on the syringe is hard as rock, there is no way that it's going in whilst the lever is against the bar and being held by minimal hand resistance. Letting the lever return without pushing in the plunger on the syringe means that the whole system is spongy as hell and the pistons will work, but not retract.

I'm pretty certain this is not a caliper issue, I've bled that according to Hope's instructions and all four pistons work just fine, it's just the system is spongy because I can't pressurise it from the caliper end. The only thing I can think of is that there must be a blockage somewhere in the line, I could just buy a new brake hose, but has any one here any thoughts or experience? I'm feeling pretty frustrated and wanting to throw the bloomin thing in the river at this moment in time.

 

[Ming the Merciless]

Is the bleed port screw on the brake lever removed and a reservoir attached to that? Have you undone the bleed port bolt at the calliper end?

 

[chriswoody]

I've got a syringe attached to the lever bleed port screw and I've tried it with both the syringe clamped shut and open. Most of the online tutorial videos I've seen, advocate the lever syringe is clamped shut whilst you perform this part of the procedure, but I've tried it both ways with no luck.

The bleed port at the caliper end is open, with the syringe attached. I've made sure the syringe is unclamped, there should be no reason why the plunger won't depress and it's really puzzling me.

Another point to add, I've detached the caliper so it's hanging free on it's hose, in order to create a straight run from the caliper to the lever with no low spots in the hose for air to trap itself in.

I have successfully bled the front system using the procedure described, so I know it works.

 

[JhnBssll]

I regularly have to tape the brake lever to the bars then cycle between vacuum and pressure on the caliper syringe when filling the RX4's for the first time. While you're pulling the syringe back you'll get some bubbles appearing from the caliper. It can take a while but you'll get there

 

[chriswoody]

Thanks @JhnBssll, I've used an elastic band to hold back the lever whilst I've bled the caliper. The problem comes during the next step, if I removed the elastic band and try let it return, whilst simultaneously depressing the plunger on the caliper syringe. The plunger just won't depress and pressurise the system, it's rock solid. This results in a soft feel at the lever and I just can't fathom what's wrong with it and what's preventing the syringe from depressing.

I have cycled the syringe a few times on the caliper and I did have some air trapped for a while behind at least two pistons, we did finally get there though. I just need to solve this issue and get a nice firm brake lever feel.

 

[JhnBssll]

So is the fluid all the way up and into the lever reservoir at this point, with the reservoir capped off again? If you're confident the caliper has no air left there might be a few bubbles in the lever. Best way to get rid of these is to pull the lever back 10mm or so and let it flick back. Do that a few times and see if it's improving things. If not you've probably still got air in the caliper.

 

[chriswoody]

There is fluid all the way through the system and when I remove the syringes the respectives ports are brimmed with fluid. Interestingly, the video on Hopes website differs from the information on their instructions. I started following the video and then switched to a technique suggested on the instruction sheet, which resulted in quite a nice flurry of air bubbles into the syringe.

I've spent a good bit of time now alternating and switching between bleeding the calliper and the reservoir, you could well be right that there is air still present somewhere. The feel is getting a lot better, but it's still a bit spongy for my liking. Thanks for the thoughts and suggestions though.