Mrs pdw brought me a bike to fix today. Shimano hydraulics, rear brake pulls straight to the bar. Start pushing mineral oil into it, and the stuff that comes out the other end is nice and clean, but yellow, just like the DOT fluid I put in my SRAM brakes.
There seemed to be fluid all over the pads, although the bike was left out in the rain this afternoon, so I'm not certain it wasn't just water.
So, is yellow mineral oil a thing, or is the reason that the brakes were screwed in the first place because someone has used DOT fluid and shafted the seals?
Probably the latter. You can tell if it's brake fluid, it smells like it and isn't particularly oil to the touch. And it'll wash off with water.
Yes yellow mineral oil is a thing - Juice Lubes for one.
Taste it. Then you'll know 😁
We often used to find yellow fluid in Shimano brakes on brand new bikes, I guess it was what they had in the factory at assembly time.
Thanks. Guess it could be legit, and there's been some previous ham fisted attempt to bleed it which resulted in fluid everywhere. I don't really trust myself to identify fluids by smell, but I did think to myself "isn't that what DOT fluid smells like?"
DOT fluids have a really nasty drying effect on skin which Mineral oils don't have. I use that as a test; not good for your skin but you only need to put a little bit on to feel the difference.
