xg5a

I bought these ST-R7025 Shimano 105 STI levers new in September of last year (first bike with discs, upgraded to hydraulic brakes so this is my first set I've installed and worked on).

Bled the brakes a week ago for the first time after install and noticed on the left lever, this circular part was oily when I peeled back the hood (forward of the bleed port, top of the master cylinder?). I'm sure I cleaned it thoroughly with isopropanol after bleeding. Looked again today after 1 ride and a week of sitting in the garage, and found oil dripping down the outside of the hood from the same place. It's definitely not the bleed port leaking, it's coming from this other area.

This is my first bike with hydraulic brakes, but I can't imagine this is normal. I did start storing the bike hanging from the front wheel a few months ago, in cast that's relevant. The other brake lever is totally dry in this area. Also got a lot of bubbles out of this brake's line when bleeding, that could be related? (this is the left lever / front brake)

When I installed these brakes, first I used a syringe to fill the system from the caliper end, until brake fluid appeared in the funnel cup. Turned the bike various ways and tapped on the lever/caliper/lines to dislodge bubbles. Then I filled the funnel cup, opened the bleed port on the brake caliper, and let some oil flow through. Last, I closed the bleed port, refilled the funnel, squeezed the brake lever, then quickly opened and closed the bleed port to get some oil with bubbles to shoot out. Repeated this until no more bubbles and the lever felt firm.

For bleeding them it was similar, but start with filling the funnel and letting oil drain through the system (no syringe used). Then do the squeeze the lever, open/close port process. (this is where I got a bunch of bubbles out of the front brake line, and basically none from the rear brake which isn't leaking)

In other news, after bleeding the brakes both rubber hoods seem "stretched out" too, is this typical? They don't want to lay flat around the top/front of the levers. The left lever is definitely worse.

Chuckles1

Haven't bled my Shimano or Tektro Hydraulic brakes yet, but I'm guessing there's an O ring on the screw in cap on top of lever. Too much or too little torque, or a defective O ring could cause a leak. I hang bike with Shimano brakes from front wheel without issues. Hood covers usually have protrusions on inner side that need to be fitted into their appropriate indents on levers in order to get covers to lay flat. Good luck.

xg5a

​​​​​​​Thanks for the info. I definitely have the bleed port plug screw in correctly with the O-ring intact, plus the area around it is dry. That was my first thought too, but this leak is definitely coming from this more forward part of the top of the hood.

Regarding the rubber hoods, I definitely have all of the protrusions on the inside of the hood placed correctly. It just seems like the hood is too big now?

Iride01 

So is the area around where the hose attaches dry? Is it possibly leaking at the brake and running up the outside of the brake line to your shifter while hanging? Clean everything you can and inspect often for the fist sign of hydraulic fluid to narrow down where it's coming from.

You used mineral oil in those Shimano brakes didn't you?

xg5a

Good thoughts, thanks. I can confirm I used the Shimano brand mineral oil. And I did already clean everything in order to find the source of the leak. The caliper and hose connections remained bone dry, so I don't think the leak is coming from there.

Crankycrank

I'm pretty sure mineral oil can soften and swell some hoods if left on too long. Try cleaning it off with some mild detergent and hope for the best.

xg5a

Here's a photo of the hood so you can see how swelled it is. In contrast, the right hood is only a tiny bit loose, after peeling it back for the bleeding. I don't think much/any mineral oil has touched that one.

Crankycrank

The good news is that your hoods are around only $15 to replace. The bad news is that where the fluid appears to be leaking is not listed as a replaceable part. EV-ST-R7025-4342E.pdf (shimano.com) You could try for a warranty claim or if no luck I'd bet that the plug unscrews and has an O-ring which could be replaced. And I would also bet that the three indentations in the plug are used to for a tool to grip on to.