A few weeks ago a mechanic friend of mine bled my brakes and informed me that the front lever was shagged. The lever seal had blown and showed me the oil spitting out the end of the reservoir.

Got a new lever (32€ via Amazon) and fitted it. Thought I’d have a look at the rear and bleed it before fitting new pads, and I find the seal in the reservoir has also blown….

Is this now a thing? Never had this problem with other shimano brakes.

M8000 levers with M8020 calipers.

What causes it?

Or…. Am I completely wrong and this is some kind of blow off valve to prevent the system being over filled?

The lever did feel very wooden with very little throw. Now it feels like the other lever.

Hmmmm

Right…. Have done another bleed on the rear brake, purposely over filling the system so that there was hardly any lever throw.
Gave the lever an aggressive pull and it squirted oil again.

Fortunately the GF is away as there is mineral oil all over the parquet floor and I may have trodden it throughout the flat, including her Persian rug and the felt rug in the hallway….. Shit.

But that would make sense, wouldn’t it? It would also mean you can add oil to the system as the pads wear and the system is able to self level.

Do the brakes work?

Yes… In the bike stand at least. Lever feel it’s there. Bike still in the stand. Will ride tomorrow.

We now need pictures of the clean up task force.😁

Pretty normal to see some fluid from around reservoir after a bleed, sure shimano mentions it somewhere. As above, as long as they work and it doesn’t continue I wouldn’t worry.

Oil should not be coming out and there is no need to add oil as pads wear – its an open system ( the rubber diaphramg acts to allow more fluid from the resovour into the system as pads wear

there is a blow off valve in some shimanos (xt,etc)
it just gets rid of excess oil

Member
there is a blow off valve in some shimanos (xt,etc)
it just gets rid of excess oil

nice one…. that puts my mind at ease somewhat, but also annoys me that i replaced the front lever for nothing.

where did you get that info? can’t find anything from shimano or in any reviews other than on forums with the odd person saying that it exists.

when mine dumped some oil I looked it up..didnt find anything 100% but this is useful

https://forums.mtbr.com/brake-time/help-deore-xt-m8000-break-leak-1009341.html

Its the way mine seem to work