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crap mechanic content....
So had a first bash at bleeding brakes last night.
Went OK. Well when I say OK, I kinda understand the theory behind it and I think with another attempt it will happen. But suffice to say that the car was on the road last night and the bike still setup on the stand with a puddle of mineral oil in a pan below.
So by that it wasn't really all that a successful venture.
I feel like I am within distance of getting this right.
Can someone please give me a quick idiots guide on the order of what to do.
For reference: XT brakes 2010 with the open bath at the top not like the newest ones.
Got the bit by the lever open, taken the top off, filled to the brim. Got a tube around the olive at the bottom by the caliper.
Filled up top, open the olive thing with a spanner, squeeze lever. Bit of oil comes down into the tube. Let go lever.
What happens next? Is it squeeze lever and open-close the olive or the other way round?
Thanks and yes I know. This is not exactly the hardest task but ho hum.
I think it's the same way hopes are done, ie:
Fill bath.
Open valve with spanner
Squeeze lever
Close valve
Release lever slowly
Repeat.
I'm sure there will be youtube video's of this!
Change of approach- get a syringe and bleed it up from the bottom. Much more effective.
But if you stick with the oldschool way, then it's squeeze lever, undo nipple (not olive btw- the olive is the wee compression thing that goes around the hose), redo nipple, release lever, repeat.
The reason is, if you don't redo the nipple before you release the lever, it'll suck air back into the system. What you want to do is suck fluid in from the reservoir instead.
nipple!
Yes that's what I meant. Missed out on some sort of LAD joke there.
Ah yes, that's what I think I did, could hear the air going in.
right got it. I think. thanks!
this syringe method. you recommend?
Absobloodylutely. Shimano recommend it now for the recent brakes too. There's 3 reasons... 1 is that air, naturally, wants to go up. 2 is that if there's limited pressure in the system (ie new bleed) then the "top down" approach is pretty erratic. But the main one is just that the syringe can push far more fluid than the lever can.
Pushing some fluid back down when you're done can help clear out bubbles from the caliper, hose unions etc so a combination of the 2 works well. You can also apply suction with the syringe to do much the same.
+1Change of approach- get a syringe and bleed it up from the bottom
+1 for reverse bleed from the calliper.
Ideally arrange bike in a workstand to make the brake hose as vertical as possible (or remove it from the bike)
I always open the reservoir, suck all the fluid out of the system with the syringe. I top it up (if its clean) or replace it if otherwise. Get all the air out the syringe, then squirt it back in, giving the hose a few taps to release any little bubbles that might be in there. Keep going until the resevoir overflows (ensure you have a bag/rags tied around to catch the excess) and until the bubbles stop coming. Close it all up, and you're laughing.
Note - wear safety glasses: high pressure brake fluid is not something you want to get in your eye. And remember to remove brake pads (to avoid contamination) and push the pistons back first.
A second syringe is handy to deal with the stuff coming out the top, rather than spilling it, btw. Pushbikes have tiny wee reservoirs.
There's a good video here. Nice clean job. Certainly a damn sight cleaner than when I do it.
if you've lost the dust cap, be really careful doing the bleed up. I pushed muck that was in the nipple, into the caliper. took loads of faffing, before eventually deciding to strip everything, out popped the muck.
Top warning Banana. 🙂
As others have said,Bleed with syringe from caliper back
thanks all!
Had a re-run saturday morning using the syringe from the caliper method.
Piece of the proverbial pee, had the little bubbles running up and 5 minutes later a properly working XT brake.
bosh.
>adds to list of things can do in mancave.
moonboy - for even better modulation, do it bottom up, as you have done, and then top down. works a treat and gets any last bits of air out