Few weeks ago I took the big bike to Antur Stiniog, front brake made that awful ” oily screech” noise. First run saw it off, but was a we bit scary all the way down. I was certain the caliper wasn’t leaking as it’s s saint, not much use, about a year old.

Took the big bike out again last weekend, same. Oil on the pads or rotor.

How did it get there? Caliper looks oil free. Forks look oil free.

I’m a bit puzzled.

Bike was on the back of the car there and back. Could that be it?

Misting from the piston seals ,?

Thisis shimano greatest feature

It doesn’t sound like you’ve actually found oil on the rotor…maybe it just needs a decent clean and once it warms up its not an issue.

Or its in the firing line from the exhaust or rear tyres and getting dirty.

Really!

I had a deore brake that did this. Changed the pads and cleaned the disc and it was ok for a ride. Came back a week later and get a horrible squeal. Did this twice before I cut my losses and replaced the calliper with a spare I had. Problem solved.

I’ve had both xt and xtr calipers do that in the past. but not one of the current ones
Id probably change the pads and clean everything first

Sounds like the caliper. Does it look a bit dusty? Change the pads, clean everything inc the rotor and try again. If it goes again then more than likely you need a new caliper.

Caliper looks spotless. No dust sticking to parts of it.

I’ll pop new pads in.

It’s still the calliper. Replace it.

have you actually cleaned the disc?

yes, i’ve had some success just ‘running-in’ a contaminated disc, but it’s never proven an effective long term solution.

boil the kettle, pour it over your disc. Or something more industrial if you prefer, but give it go…

How do you store the bike? Hanging from back wheel maybe it’s dripping off a freshly lubed chain?

Also, as above – in the firing line for gunk from the exhaust/road grime off a tyre?

Bike is stored with back wheel on the ground. Front wheel goes into a hook on the wall, so it doesn’t fall backwards.

Might just get a new caliper… Not terribly chuffed.

my rear zee is doing the same at the moment. its stored in the same way as the OP’s bike.
was making a horrendous howl on sunday coming down jacobs ladder. sounded like i had a vuvuzela stuck in there.
i lock the brake completely and can still pedal the bike so it has very little bite. cant see any evidence of a leak on the caliper.
however the lever always feels spongy when i get the bike down and it always needs a few pumps even though it been bled…so i know there is still some air trapped in there.
gonna carry out a full clean of the caliper and rotor, re-bleed and change the pads this weekend to see if that sorts it…if that doesnt work then its going back to CRC for a warranty job/replacement

EDIT: OP try putting a sheet of tissue in the caliper between the pads and rotor and leave it over night. if there is a leak at the caliper it will show up on the tissue

Bought a new caliper, life’s too short to spoil weekend plans involving riding…

As mentioned above it is a seemingly common Shimano failing. Just discovered that I have the same problem by wedging cardboard in the caliper and clamping the brake lever on overnight.

Had been trying to source the squealing and ever deteriorating performance for months.

New brakes being fitted at the weekend.

Just found out, I bought them 29Sept, 2014, any chance of warranty if I act rapidly?

Shimano provide a 2 year warranty. Unfortunately you’re a day out. They may do it out of goodwill, you’ve got nothing to lose. Caontact the shop/mail order giant where you bought them from and see what they say?

Ive got Deore on my xc bike and used to store it vertically in a cupboard wth the rear wheel on the ground and I had exactly the same issue. Since I stopped doing this, I’ve had no further problems.

Of course, I had to change the pads and clean the rotors, but I did that before I stopped and it was still and issue.

You think gravity was making it leak out or something ?

Lack of use probably dried the seals out.