Brake bleeding hints and tips

[foz]

No, I don't have any. But I need some... Brakes are early Magura HS33, but I think brake bleeding is probably more a post 98 thing, as before then there weren't that many hydraulic brakes.

Have watched the Magura video, and it seems so simple. I'm using a homemade kit, which admittedly might be part of the problem, but I don't think so. Maybe it's just the brakes I have are bodged together and not the best.

I think the main problem I'm having is that when I loosen the bleed screws to connect the bleed hoses, oil just starts leaking out, and gets everywhere! This happens both when connecting and disconnecting the bleed hoses, and I think I have air in the system because of this. It doesn't happen on the videos I've seen! There, the bleed screw is undone, and maybe a drop will leak out, no more.

What am I doing wrong? I'm using Shimano hydraulic oil. Is a proper bleed kit really worth it? Looks just like hoses and syringes, is there anything special about the proper ones?

Any other hints and tips would be great!

 

[dazdc5]

Re:

How far are you undoing your bleed screws.. quarter to half a turn is usually my limit.

I always make sure the fluid bottle has been stood for a couple of days and am really careful when extracting from bottle to syringe NOT to get any air bubbles so go slow when you draw up the fluid, with your short length of hose on your syringe gently 'push' untill fluid is level with end of hose section.
Your piece of hose to connect to the caliper shouldn't leak on the bleed screw .. sounds like it may be too big, put spanner over bleed screw then attach hose, open bleed screw and with your syringe upside down (plunger facing up) draw some fluid out of the caliper first (assuming you have opened your brake reservoir cap) to get rid of any air trapped and let that rise up and out of the way, then gently push the plunger down but stop and re-tighten your bleed screw before you stop... and don't push so far that you push the bubbles back into your system... remove capture vessell off your reservoir and re-fit bleed valve.

Works for me until I cook my fluid trying to slow down off Happy Valley on the Malverns. :roll:

 

[My_Teenage_Self]

All I use is one large syringe, Lots of LHM a short piece of tube and a single magura barbed fitting. The important thing is to refit the lever screw, then the caliper screw.



viewtopic.php?f=1&t=408841

"TBH, all the maguras I've had have responded perfectly to the following, but I've never done a tandem...

Get a LARGE syringe - 50ml should do it for a tandem (I normally use a 20ml). You'll need tubing and adapters for it to screw into the rear caliper.

Remove bleed screws at the lever and caliper. Fill the syringe with LHM (No air bubbles at all)and screw it into the caliper.

Have a helper hold the lever in a towel or rag, bleed port up, and blast most of the 50ml through the system - push it through HARD.

When almost done, and still pushing LHM through, flick the lever a few times.

With the last few ml being pushed in, refit the lever screw. Then remove syringe and fit caliper screw.

All the waste fluid is in the towel/rag. It's a messy way of doing it, but has worked 100% for me"

 

[Bullpup]

The key to these is making sure the slave pistons move freely. I remove the pads and clean the surrounding metalwork carfully. Then use the master cylinder to partially push out the pistons then lubricate freely with XCP One and work them via the master cylinder until both moving freely and evenly - If necessary hold one piston in with a thumb while working the other. Then clean off any excess residue before installing.
As others have said, keep the master cylinder as high as possible and use 2 syringes. When you are ready to seal the system do the master cylinder first and then turn it upside down so the bleed on the slave is uppermost before removing the syringe.

 

[foz]

Thanks all for the advice. I think the lever might be not working, which won't help things... and the slaves aren't in the best condition either. I have others I can try, but connecting everything and bleeding each time just to check which ones work best together is a bit of a faff...

Are the master cylinder (lever) and slave pistons serviceable? Can they be taken apart, cleaned, and reassembled with new seals?

on the bleeding, I like the idea of turning the brakes upside down once the bleed screw is put back in at the lever end. I think I will uninstall from the bike and get them sorted, then fit again. Fitting is a pain too, it's only worth it because when they do work, they work so well...

 

[Bullpup]

I have had some master cylinders which have become gummed up etc. I remove the hose and bleed screws and put them in a bucket of hot water with a fairly strong mix of biological washing powder in it. Work the lever fairly regularly to draw the liquid into the system and repeat fairly often. Can take several hours to come right.
When working, repeat with plain water to rinse out, then pump out in the air and leave to drain. Then connect the 2 bleed syringes and work some LHM fluid through them before connecting and bleeding as normal.

This will probably work with the slave cylinders as well - in fact you could just force the detergent mix in with the bleed kit.

I would suggest you try cleaning then lubricating the slave cylinders as outlined above. Use some brake cleaner and an old tooth brush to clear the muck first. This has worked for me even with some particularly stuck brakes where somebody had used very old cooking oil.