Bleed fail

[gil goshen]

Hi there,

I recently started experimenting with fixing my bike on my own. I tried to bleed my hydraulic breaks on my own, and I thought I did everything by the book, but when I closed the screw that can be seen in the video, it spits out the oil every time I squeeze the breaks. I didn't know if I should just screw it stronger, and I was afraid to go any further because the screw was already a bit eaten up...

Any insights on why this has happened to me?

By the way, it has also occurred to me that maybe I should not have opened the screw at all in the first place and just tried to squeeze the oil with the syringe through the valve of the screw. As I said - this is my first time bleeding, and I could not find any info or videos with this type of screw.

Thank you!!

 

[I like Skol]

Hi Gil and welcome to the forum.

Glad you are trying to tackle a few bike repairs yourself, bicycles are not very complicated and with YouTube and forums etc it's often easy to learn how to do a lot of the straightforward jobs. Unfortunately, bleeding brakes seems to be one of the trickier jobs that otherwise experienced diy'rs can sometimes struggle to master.

First of all, why did you want to bleed the brakes? The mineral oil used in most hydraulic bicycle brakes has a long service life and usually doesn't need any attention unless something else is wrong, unlike the automotive DOT brake fluids used in the more unusual bike brakes which absorbs water and has to be routinely replaced as a result.

Looking at your picture I would hazard a guess that you have removed the bleed nipple completely and then put it back in cross-threaded so it isn't sat straight and can't seal. It might be the angle of the picture but the nipple doesn't look straight to me. Unfortunately the leaking oil is likely to have contaminated the brake pads so they will need to be replaced once everything has been fixed and thoroughly cleaned up to remove all traces of oil, especially from the disc/rotor.

The bleed nipple ideally needs replacing. As you already say, it is badly chewed up. These should always be undone with a ring spanner of the correct size, probably 7mm. If the old nipple has been inserted cross threaded you will need to check how much damage has been done to the thread in the caliper body. You might be lucky and get a new nipple to thread in straight, if not it is new caliper time. If you do manage to get a new nipple to screw in ok you should know that there is no need to remove the nipple for bleeding. Opening the bleed nipple usually only takes around half a turn or less and this is enough to let the fluid purge out through the hole in the centre of the nipple. This will also prevent any chance of cross threading the nipple when removing/refitting. Use a small length of clear plastic tube to direct the expelled fluid into an old jar or bottle and the clear tube allows you to see when the fluid is coming out clean and free of bubbles.

Just one last thing. The brake hose looks like it has been strained/damaged at the nut where it enters the caliper. This is a weak point and likely cause failure in the future if it deteriorates or in a sudden emergency braking situation. If you have enough slack in the hose at the handlebars you will be able to trim the end of the hose by 20mm or so and refit with a new olive and hose insert. If the hose is already short (possibly the reason it is strained already?) then it will need an entire new hose.

Maybe at this point it might be more practical to let a bike shop take a look at it. They may well have a good nipple from an old caliper that will fit and will be able to identify the fittings or complete hose as required.

Good luck

 

[Big John]

Don't make a bad situation worse. Take it to a trusted local bike shop.

 

[Brandane]

Probably too late for your bleed nipple, and possibly also the caliper if the thread is mullered. But for next time:



Wouldn't worry too much if you HAVE wrecked the caliper, they aren't overly expensive to replace. Might even be able to find one on the usual second hand sales sites. Ebay etc.. But a replacement WILL have to be fitted correctly and bled properly.

 

[I like Skol]

Hey OP. If/when you manage to sort this please come back and update us on what the solution was.