bleeding Shimano br...
 

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bleeding Shimano brakes - part 232-leaky bladders?

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Despite a new caliper, my rear brake  is still weak and getting noisy again. 

I put a new bladder in the front, and the old one looked good so I put it on the rear lever

After every ride  there has been room to put more fluid in. I just bled it again, with a syringe each end., and finally tried squeezing a bit more oil in, which i saw leaking out of the lever outside end (the bit that the bladder is attached to.)

SO..Is the oil supposed to come out of there, or is it definitely a leaking bladder? Thats probably where the lost oil came from.

I seem to remember that that was what the hole there was for- to eject excess oil if it expanded due to heat etc., but Im not sure anymore

 
Posted : 13/09/2025 2:28 pm
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Posted by: alric

Despite a new caliper, my rear brake  is still weak and getting noisy again

Assuming you have a solid feel at the rotor, this sounds like contaminated pads to me. Cleaning the rotor with hot water and detergent, then sanding it and fitting fresh pads should eliminate that possibility. The new pads will need to be bedded in, obviously.

If the lever is spongy, it's a bleeding problem.

You might also have a bleeding problem plus contaminated rotor and pads.

 
Posted : 13/09/2025 3:33 pm
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Posted by: thols2

Posted by: alric

Despite a new caliper, my rear brake  is still weak and getting noisy again

Assuming you have a solid feel at the rotor, this sounds like contaminated pads to me. Cleaning the rotor with hot water and detergent, then sanding it and fitting fresh pads should eliminate that possibility. The new pads will need to be bedded in, obviously.

If the lever is spongy, it's a bleeding problem.

You might also have a bleeding problem plus contaminated rotor and pads.

Its not that, I tried all that before, when i put the caliper on, and the lever's not spongy

 

 
Posted : 13/09/2025 4:08 pm
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Sounds like a leaky/dislodged bladder. The expansion chamber is just air and it shouldn’t have any fluid in it seeping past the bladder. If you’ve over filled it maybe it’s dislodged the bladder….

 
Posted : 13/09/2025 5:08 pm
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Main piston in the lever has failed IMO. 

 
Posted : 14/09/2025 9:31 am

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