The plunger in my syringe is sticking (fnarr, fnarr). What can I lubricate it with, that won’t contaminate the mineral brake fluid I am putting into my Shimano brakes?

Mineral brake fluid would be the obvious answer but it’s more likely the seal has swollen due to some reaction with the fluid.

My answer was going to be spit, which made me laugh. I looked for a video of someone doing one of those big long spit strings where they suck them back up and found this

[video]https://www.youtube.com/watch?v=BV4ZeNvXfhk[/video]

The problem is that the seals in the syringes are intended to be used with water based fluids (i.e. blood, and stuff that can be injected into it).

Brake fluid and mineral oil aren’t water so they swell the seals.

So the options are:
1) Invest in some expensive glass syringes without seals.
2) Invest in the real bleed kits not epic/ebay copies and hope the manufacturers had proper seals made.
3) Buy a box of syringes (ebay, pharmacist), they work out pence each and usually last one bleed if you work quickly before the seals swell up.

The syringes that most bleed kits include are actually single-use disposable syringes not intended for that use.

Bin it and get a new one. If it has has a threaded tip you need a luer-lock syringe.

Basically the only interesting bit in most bleed kits is the connector on the end that threads into the brake, everything else is standard- the syringes cost pennies on ebay so I just bought a wee bundle.

Leaving the syringe drawn back slightly so that instead of having to pull it back against suction- which can take the plunger head right off- you’re pushing into the syringe, also helps.

Buy a few disposables from either eBay or here – medtree

use what ever is going in the syringe

Thanks folks, bought a pack of five off eBay. Binned my old ones.