• This topic has 22 replies, 13 voices, and was last updated 2 years ago by Bream.
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  • Magura bleeding problem – help please
  • Premier Icon svensvenson
    Full Member

    OK, further to the thread of several days ago, I have duly parted with some of my hard earned (well relatively hard earned) cash and bought a set of MT5s. They arrive with a generous 2m of hose, so duly cut down to correct length, using the correct tools in the bike shop at work etc. I also bought a magura bleed kit – which proved to have a vast selection of bits and bobs, (great) and two of the s*%#$st syringes ever (not so great).

    Either way after borrowing one of the pro bleed kits from the bike shop I still can not get them bled correctly. And yes I have followed various tutorials etc. Now I’m not an idiot either, I’ve just never had this problem before, either on bikes, motorbikes or cars!

    This is a little frustrating – not helped by my son cracking the swing arm on my other bike… grrrrr. (although unlikely to be his fault considering his paltry 40kgs and my “svelt 75…)

    Anyway if the collective hive mind has any experience of the same problem and ideally a solution, I will eternally grateful. Or at least until next week.

    thanks

    Steve.

    Premier Icon dmw536
    Free Member

    Mate of mine had similar issues with a pair of the new Magura brakes. He managed to bleed one perfectly and the other no joy, to the point where he just returned one of them! No idea what the issue was.

    He claims not to be an idiot too.

    Premier Icon svensvenson
    Full Member

    Hmmm… well I’m glad he’s not an idiot. (although not that many people claim to be idiots…)

    Premier Icon paulhaycraft
    Full Member

    I bled some Maguras for a mate a couple of months back and ended up doing them twice. I followed the instructions very carefully (very, very carefully the second time with not much improvement).

    They seemed to bleed through ok but the whole system just felt a bit spongy. They still stop ok but there is a lot of movement in the lever from rest to fully applied but almost no ‘free throw. in the lever before the pistons moved.

    They were better than when I got them so he was happy enough.

    Premier Icon svensvenson
    Full Member

    yeah, well that’s what I sort of get, but they really don’t work. The reason I bought them is one of the other mechanics has a trials bike with them on and they’re bloody amazing – no sponginess at all, so I kind of miffed (understatement) that mine are so useless. not had my last word on the matter though. I spent 8 hours in a gymnasium yesterday watching my daughter (for 4 minutes) which gave me plenty of thinking time.

    I’m thinking of doing the inverse of the directions when it comes to unplugging everything after the purge – on the principle that it can’t get any worse…

    thanks for the info though – it all helps.

    Premier Icon bigyan
    Free Member

    If the proper bleed procedure wont work and you have re orientated the caliper/lever to remove trapped air/high points I would try gravity bleeding them.

    Premier Icon luke0912
    Free Member

    When I bleed my mt5’s it took about 10-15 minutes of cycling the oil from the caliper up to the lever before any air bubbles emerged, then all of a sudden a load appeared and the lever feel was much better.

    Premier Icon svensvenson
    Full Member

    ok, stupid question perhaps, but please humour me: gravity bleeding? what is that exactly?

    Premier Icon weatheredwannabe
    Free Member

    If all else fails, rather than use the plunger less syringe method, suspend a clear bottle 1/2 filled with mineral oil with a bit of wire coat hanger etc from the handle bars and run a flexy, thin, clear 4mm tube fully inserted into the fluid in the bottle and stick the other end with an insert into the bleed port on the leveled lever. Proceed as normal with the syringe at the caliper end, the extra draw force should do the job. Also have the caliber and lever as vertical as you can get from each other and lightly tap the cable, caliper and lever with a screw driver to help release the bubbles.

    I’ve used a  semi filled syringe with the plunger at the lever before, which worked very well a few times, but once I blew the seals out, so don’t do that any more………You can’t buy Magura replacement seals and have to replace the whole unit. ( which really sucks imo )

    Premier Icon dubber
    Free Member

    Make sure the syringe in the levers is pushed in far enough – I was drawing air in on the back stroke when pulling at caliper as I hadn’t created an air tight seal.

    Remove calipers and make sure the 2 bolt holes look like ears on the caliper so the syringe is attached at the highest part .

    I thought I’d got all the bubbles out , but there were a lot of micro bubbles that I could just about see .

    https://www.bike-components.de/blog/en/2017/05/how-to-replace-the-brake-fluid-and-bleed-magura-mtb-disc-brakes/

    Premier Icon mucker
    Full Member

    I take it you’ve got the Magura disc’s as well, they’re a bit thicker than most other manufacturers.  I didn’t originally and was not getting a result I was happy with when bleeding my MT5’s.

    Premier Icon BearBack
    Free Member

    I love magura brakes, there probably hasnt been a brakeset better than the marta sl. Anyway, it was bleeding magura brakes that has me intonthe shop with anything more than a master cylinder bleed.

    Jude monica has a number  of tutorials. I think the biggest frustration i remember was pull:pull bleeding with a sealed syringe system. You just end up ‘cavitating’ the fluid or whatever the term is.

    A few time i though i had it dialled but then pulled the bleed block and blew the pistons out…

    Push:pull with an full but open (plungerless) syringe in the lever bleed port seemed the best but its supposed to be a dozen or so repeats.

    This is older generation brakes, ive not done any mt# but i do have a new set of mt8s that im thinking of using on a project…if only bleeding was easy 😉

    Premier Icon bigyan
    Free Member

    ok, stupid question perhaps, but please humour me: gravity bleeding? what is that exactly?

    For MT5s screw a syringe with the plunger removed into the lever, partially fill it, remove the bleed plug on the caliper and let the oil gravity drain through the brake, hopefully you will get some air bubbles at some point, refit the bleed plug when there is still fluid in the syringe. Slow but normally always works.

    Make sure the lever bleed screw is the system high point,and the caliper bleed screw is the caliper high point, its not unusual to have to remove the caliper from the frame/fork and move the lever on the bars. If the hose routing on the rear brake creates a high spot some creative angles may be required.

    You can also use a syringe with the plunger removed in the lever as a resevoir for a traditional pressure bleed, pull lever, open bleed screw on caliper, close bleed screw, release lever and repeat. Finishing doing this on any bleed tends to ensure a good lever feel.

    Applying a vacuum can easily suck in air if the syring seal is not perfect, pressure bleeding with a slight leak can make a mess, but does not introduce air into the system.

    At the end of the day you need the system full of oil with no air, there is more than one way to skin a cat.

    Premier Icon svensvenson
    Full Member

    thanks everyone. I shall be trying all of this in increasing order of complexity this evening… I’m thinking that taking the system off the bike will simplify things, and that maybe reverting to motorbike style bleed techniques (bigyan thanks for the reminders)…

    anyway I’ll shall let you all know how it pans out.

    Premier Icon Bream
    Free Member

    I had weeks of similar issues bleeding my MT8s over an over again, could even get it clear only to lose pressure half way through a marathon race. Got to the point I was looking to scrap them and buy a different set!

    In the end I solved it by not using the Magura bleed kit and instructions as on Youtube, but instead using my SRAM bleed kit parts. My problem was as mentioned above, sucking in air from the lever syringe under vaccum. To properly bleed it I had to use a lot of vacuum pressure to pull the air out and I could do that once the lever leak was solved.

    So decent syringes with tight fittings and high vacuum seems to be the solution.

    Premier Icon svensvenson
    Full Member

    thanks Bream, I get the theory, but how do you get a tight enough seal at the lever? it’s only a plastic thread. I did try endlessly pushing the fluid through from caliper to lever, something of a performance and it didn’t really work either, but thinking the same thing that I was getting air in the system when drawing the fluid back down. so just keep pushing it up right?

    ho hum. I foresee a little lunch time project, probably aided by 4 or 5 mechanics giving helpful and contradictory tips at the same time…

    Premier Icon wwaswas
    Full Member

    I use the two syringe method and cycle the oil both ways a with a few lever squeezes ever so often. Pushing fluid in witht the top and bottom syringes alternately (let the fluid pressure force the opposite ends syringe piston out to accept the oil) seems to avoid that thing of drawing air in with a vacuum.

    To get that really firm lever feel I’ve tended to let the pistons stick out the caliper a fair bit (so they have to be pushed back in to fit the pads and clear the disk when it’s finished).

    they do seem a bit sensitive to getting air in them when disconnecting everything I’ve found.

    Premier Icon svensvenson
    Full Member

    FINALLY.

    one of the guys at work found a video with a guy in it rocking the lever from just above the bar to just below, whilst working the action, syringe in the top and closed off below. (that make sense?)

    either way out come the bubbles and after 8 hours(!!!) 10 minutes of faffing and its done.

    thanks everyone for your input/suggestions etc. If anyone actually needs to understand the garbled explanation above, please just ask and I’ll make it clearer, but right now I’m going home!

    Premier Icon matt_outandabout
    Full Member

    Those cheeky last hiding bubbles, eh?

    Premier Icon dubber
    Free Member

    one of the guys at work found a video with a guy in it rocking the lever from just above the bar to just below, whilst working the action, syringe in the top and closed off below.

    The link to that video would be great if possible thanks .

    Premier Icon svensvenson
    Full Member

    as asked. it’s in French, but the pictures are worth a thousand words, or something like that.

    It’s still not a “fast” procedure, but the satisfaction in getting those last f*$#&g bubbles out…

    Either way hopefully I won’t run directly into any trees tomorrow night… or least because of not having any brakes.
    <p dir=”LTR” align=”LEFT”><span lang=”EN”>https://www.vtt-alsace.fr/viewtopic.php?t=2251</span&gt;</p>
    As I said above if anyone wants to know more please just ask.

    thanks again everyone,

    Premier Icon Bream
    Free Member

    Glad you got it fixed, just be prepared for it to lose pressure after a couple of hours riding if not! Lol, bad joke.

    Think my SRAM syringes fitted better in the lever port, so when I pulled out the oil from the caliper it pulled down the oil/syringe from the lever. Creates quite a high vacuum doing it this way as you’re pulling the oil through rather than pushing it through, but this was what solved my problem.

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