Bleeding hell

mylovelyhorse

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Is there some special trick to bleeding the brake fluid on a 2012 F800GS with ABS? I have one of those vacuum things and I have run about 500ml of fresh fluid through the braking system but I cannot get the air out. I can't tell how much air is in because the nozzle of the vacuum thing doesn't quite fit on the brake nipple and some of the brake fluid is kindly leaking out round the base of the nipple anyway. I can tell it must be quite a lot as I can rather easily pull the lever back to the bar...
 
If the nozzle is not tight then you are not creating a vacuum which is why you are getting air into the system. I used to use the same thing and it was ok but I started having the same issues. Get rid of it and buy a little bleeder, one of those simple one way liquid valves. You put the pipeover the nipple, loosen it and simply pump the brake lever. Once the liquid gets to the valve it can get passed but not back which stops air getting in. You then just keep topping up the reservoir until you have fresh fluid throughout the system. Takes minutes and the valve costs a couple of quid.
 
A good way to back bleed is to use an oil can, the one you pump oil onto a chain etc, clean it out and fill it with brake fluid. You then need a piece of pipe which is a tight fit over the nipple and the end of the oil can pipe. Get rid of as much air as possible from the pipe by pumping fluid through it then push it over and Loosen the nipple. Remove the top on the reservoir and pump the oil can gently. You will need a syringe to remove the fluid from the reservoir. Typically this is a good way of pushing air out as it tries to rise. Periodically tighten the nipple and squeeze the lever for feeling, sometimes it may help to zip tie the lever to the handle bars over night to let any trapped air escape
 
Feck me have things moved on and I don;t know??

What happened to getting someone to top off fluid and pump whilst you collect the remains in a bottle with a small length of windscreen washer tube, which is raised up away from the bleed nipple before it runs down into the bottle, so that air goes straight up without getting sucked back into the calliper?????


P.S. Make sure that you do NOT get ANY engine oil mixed with the brake fluid just in case you follow the above method! its a surefire way to feck up brake seals

If you want to back bleed go to a farm shop or a vet supplies or Vet and get a 60 ml syringe and use that with a length of windscreen washer pipe
 
Feck me have things moved on and I don;t know??

What happened to getting someone to top off fluid and pump whilst you collect the remains in a bottle with a small length of windscreen washer tube, which is raised up away from the bleed nipple before it runs down into the bottle, so that air goes straight up without getting sucked back into the calliper?????
You need a friend and I haven't got any boo hoo :fiddle:fiddle
 
Found a set of the Stahlbus anti-return bleed nipples in the bottom of a box (new too). Must have bought them a couple of years back and forgotten about them. Fitted them this lunchtime and ran brake fluid through until it was patently both clean and bubble free. Pumped the brakes a bit with the nipples closed, ran it up and down the road, got a little (little) more air out and generally played gentle percussion on the hoses and calipers in case there was anything still in there. Bled them again - no air seen this time. Still not getting a firm lever. Packed it all way mightily confused and put a zip-tie on the brake lever. Won't be around during the week so I shall look at this again next weekend.
 
Ok, pardon my lack of knowledge with the 800. On the 1200 you need the gs911 to open the ports on the abs pump/block to enable you to purge the whole system. Is it the same on the 800? I don't know but someone will. Also as the abs is powered by the bike you will need to bleed the system with the engine running to get the pump working. To be honest I've never had an issue bleeding the brakes on an abs bike but that may be because I've been ultra aware not to get air back into the system and just kept using brake pressure to do the work. If air has got in and worked its way back to the pump then it is just a case of keeping at it I'm afraid. It really can only be air trapped in a pocket somewhere.
 
Ok, pardon my lack of knowledge with the 800. On the 1200 you need the gs911 to open the ports on the abs pump/block to enable you to purge the whole system.
Not found that to be true on my 2011 1200 nor have I found it necessary to have the engine running. I've found the trick to pressure flushing and bleeding brakes with the levers is to do it fast to push the bubbles down the lines and not pause as the flow rate of the fluid has to be such that the bubbles don't have chance to rise back up. One difference between the 1200 and the 800 is that the latter has one line to the right hand caliper and a hop over line to the second caliper. The hop over line has a high spot which can allow air to rise and sit there if you don't push fluid through quick enough. A different reason why pressure can't be achieved at the lever is if the main piston seal is shot. Squeeze the lever and the fluid leaks round the seal rather than pressurizing the lines: release the lever and it seeps back into the system without any loss of fluid. I've tried vacuum systems without much success, finding that the vacuum sucked air round the bleed screw threads. The answer is I think, pressure flushing, either reverse flushing into the bleed screw, or pumping it quickly with the lever from the reservoir.
Alan R
 
If your not splitting the system the best idea when changing the fluid is to do it without getting air in the system in the first place, just pump fresh fluid through until its clean and then a bit more to be sure keeping the reservoir topped up as you go, I have done this loads of times on lots of different bikes and never ended up with air in the system.
 
So there is a final resolution to all this.

According to the mechanic at my local BMW dealership the anti squeal springs were in the wrong way round - i.e. with the little arrow pointing the wrong way. This stopped the pads moving and left the lever feeling like there was no hydraulic pressure.

The brakes are excellent now, the bike has its MOT and I just need to get 1k miles on it before going to Chimay in mid July :)



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