Bleed or flush old oil before brake removal and storage?

Question

I'm about to replace my stock Shimano BR-MT400 hydraulic disc brakes. The cables are external. I think I have a sense of how to install, bleed and bed-in the new Maguras, but is there some best practice around removing the Shimanos to keep them in working condition? In the short term, they're going into the parts bin, but they may eventually get put on another bike or donated to the co-op.

Specifically, is there any harm in letting the oil sit in the system or should this be flushed out before these brakes go unused for a while?

Any other recommendations for safe and sound removal are welcome.

Answer 1

The existing mineral oil will be fine. It’s stable over a human timeline. There might be microscopic amounts of water in the line but it’s sealed.

I would be more worried about the aluminium and magnesium parts corroding so when you store them if your local environment has a potential for corrosion

• Remove the pads.
• Push the pistons in as much as possible with a soft tool.
• Install a spacer between the pistons.
• Wash the set with your favourite cleaning product, dry.
• Lightly spray the callipers and levers with some WD40 to leave a protective film.

Coil up the set into a relaxed ~250-300mm circle and zip tie. The brakes ship coiled from the manufacturer so don’t worry about the coils bedding in. If you ever use them again you can decide then if you want to bleed.