shimano caliper leaking

[SolemnWeasel]

I am now convinced that the BR-m525 rear caliper of mine is leaking - with light reflection I can see oil weeping in the middle when I brake. I don't think it is the piston seals gone.
That explains why they squeel extremely and loose power for the second time now.

I am wondering - should i replace with the cheap Shimano BR-MT200, or try to troubleshoot and maybe replace the O-ring? Or buy better caliper.
I hope I could reuse the lever and hydraulic line.
Never replaced hydraulic parts yet - I understand I need an olive and 'barb' to install?

Thanks for tips.

 

[wafter]

When you say "weeping in the middle" do you mean between the two halves of the caliper?

IMO always worth trying to save stuff; while you have nowt to lose if you're prepared to replace it anyway. Presumably the caliper halves just bolt together with fluid drillings sealed with O-rings / a gasket / sealant?

IIRC I vaguely recall watching a caliper strip on youtube; didn't seem terrible.


EDIT: Not your caliper but I'm sure they're all much of a muchness; looks straightforward with the only potential pain being piston removal if you don't have a source of compressed air.

 

[SolemnWeasel]

Yes, it is weeping / leaking between the two halves - very difficult to see - I only noticed when I saw that light reflection changed when pressing. I might go to a bike self repair place and see if they have o-rings for it.

 

[SolemnWeasel]

The solution to that is that I bought a new brake caliper, a BR-MT410 Shimano one. I installed it, only to see it is also leaking in a similar way.
Just to note the front brake is also an m525 and has absolutely no signs of leaking.

The MT410 can be seen here
View: https://www.youtube.com/shorts/aMT5XIqDvE0 (loud noises).

In addition to the 525 caliper - I opened it and the o-ring looks to be around 6mm and a bit in diameter.
Measured on the resceptacle for the o-ring - 6.3mm, the oring itself looks to be 6.1mm - I think I am reading this correctly.
Probably a 6mm o-ring will be fine then, preferaby thicker.

 

[Yellow Saddle]

The solution to that is that I bought a new brake caliper, a BR-MT410 Shimano one. I installed it, only to see it is also leaking in a similar way.
Just to note the front brake is also an m525 and has absolutely no signs of leaking.

The MT410 can be seen here
View: https://www.youtube.com/shorts/aMT5XIqDvE0 (loud noises).

In addition to the 525 caliper - I opened it and the o-ring looks to be around 6mm and a bit in diameter.
Measured on the resceptacle for the o-ring - 6.3mm, the oring itself looks to be 6.1mm - I think I am reading this correctly.
Probably a 6mm o-ring will be fine then, preferaby thicker.

I have a huge selection of O-rings. If you want some, I can probably help. You need to measure the ID and the diameter of the "O". for instance, 6.5 x 3