Dodgy shimano hydraulic road shifter?

[Sensibleboy]

My front disc brake on my 5 year old Trek Domane 4.5 disc is playing up.

The lever is pulling all the way back without putting much pressure into the caliper. It is still moving the pads slightly. Theres no sign of leakage. They've never been bled since new.

If I pump the lever a few times the pressure will build slightly and the lever has less travel.

I'm not sure if the lever is knackered or it just needs a thorough bleeding.

Any ideas what the problem might be?

[NorthDave]

Sounds a lot like air in the system to me. Give it a bleed and I'm pretty sure you will be sorted.

[Juffled]

I find this happens all the time when I store my bike vertically. It's fundamentally air in the system.

[Sensibleboy]

I've ordered a bleed kit so hopefully that will fix it. How does the air get in though?

[frisbee]

Sensibleboy said:

I've ordered a bleed kit so hopefully that will fix it. How does the air get in though?

There are bleeding instructions in the Shimano service manuals. Fairly easy to find on Google.

Air can get in gradually over time, if the bike is stored at a funny angle it can also cause it.