CanadianBiker32

I was trying to unstuck my htydraulic brakes - rear on fat bike.
turned the screws on the level and a little bit of fluid came out. was i was just trying to pop out the air a bit. Pushing the pistons abit.
However now when i squeeze the level. there is no pressure whatsoever?
Not much fluid came out , just a few drips more less. But maybe i need to put some in?

Suggestions?

Right now the pistons are wide open and wheel spins freely. yet i have no brake pressure?

Also if i need to put in new fluid .
could i use DOT 3? from my auto selection?

i am usually able to get things working on my own bike . i want to get this properly working on my own
trial and error I am ok with and works with me usually
suggestions? thanks

cxwrench

How about you tell us what kind of brakes you have before you go do anything that could cause major problems.

Iride01 

Definitely depends on what brakes you have.

How where the brakes stuck that made you want to screw with them?

sch

One place to start is here: https://www.parktool.com/blog/repair...a%5B%5D=153809
You can also do a search on youtube for how to adjust/bleed bicycle disk brakes.
You can also search the website for the maker of your brakes for online tech support.
BUT you really really need to know what kind of brake fluid is used in your brakes, some use mineral oil
and some DOT and using the wrong one will ruin the seals in the other.

CanadianBiker32

Alvio

Cyclist0108

https://si.shimano.com/pdfs/dm/DM-BR0005-13-ENG.pdf

You need Shimano mineral oil. DOT fluid will destroy them.

dsbrantjr

Get some help from someone who can put eyes and hands on the problem and who knows what they are doing. As a safety item brakes do not lend themselves to trial and error maintenance/repair.

gsa103

This video will show you what you need to do:
You need Shimano mineral. Using DOT brake fluid will destroy the rubber seals and ruin the brakes.
You can buy a bleed kit including oil for about $20: https://smile.amazon.com/dp/B087ZZHN..._fpfNFbJVNYH4N
If you're comfortable working on cars and other things, buy the kit and fix it yourself. If you're not comfortable working on your car, take it to the bike shop.
They should be able to sort it out for $20-50 (depending on shop and location).

CanadianBiker32

thanks so much

cxwrench

Being that they're Shimano it probably says right on them 'Shimano Mineral Oil'...

CanadianBiker32

Just a question I watched a video of something using Baby Oil in the brake lines? would this be ok too? or should i stay away?

gsa103

Possibly, some people say it works. You have no way of knowing when or how it will fail though. Baby oil freezes at -4C, so I doubt it will work in cold weather, since you're Canadian that's probably relevant. Even if it doesn't fully freeze, its likely to thicken in the cold degrading braking performance. Keep in mind that if the oil actually freezes there's a chance it would do permeant damage.

People have experimented with different replacements for Shimano oil, but most of the more reliable automotive fluids (Pentosin 7.1 is mentioned) are similar cost so there's no real benefit. Every bike shop will have Shimano oil if you need to locally source it. The little bottle has enough to bleed most brakes twice, so the bottle lasts a very long time.

CanadianBiker32

so far i think i must lost all fluid. as no pressure on brake lever. like nothing

trailangel

Did you take the brake pads out?

CanadianBiker32

yes
i pushed the pistons in too
now there is nothing

Amt0571

It probably works. But buy proper fluid. It's not that expensive and it's way cheaper than a dentist.

CanadianBiker32

I made a mistake on the brakes. The brand is AVID

CanadianBiker32

CanadianBiker32

Looks like I should be using Dot 3?

Amt0571

You can use DOT3, but it would be ideal if you could use DOT5.1.

You also need a bleed kit. Avid brakes are more difficult to bleed than shimano. Search how to do it on youtube.

ARider2

It sounds like you make just need to bleed the system to purge it of air but first make sure there are no leaks. Pay close attention to all junction points of the hoses and also check the calipers for signs of leakage. It is important to note that bicycles with hydraulic brakes should be kept upright, not turned upside down, not even put on its side, or this may cause air bubbles in the system. This is from the Shimano safety instructions (document SI-8KC0A-001-00) for their Deore disc brakes:

"When turning the bicycle upside down or on its side, the brake system may have some air bubbles inside the reservoir tank which are still there when the bleed screws are replaced, or which accumulate in various parts of the brake system when it is used for long periods. This disc brake system is not designed to be turned upside down. If the bicycle is turned upside down or on its side, the air bubbles inside the reservoir tank may move in the direction of the calipers. If the bicycle is ridden in this condition, there is the danger that the brakes may not operate and a serious accident could occur. If the bicycle has been turned upside down or on its side, be sure to operate the brake lever a few times to check that the brakes operate normally before riding the bicycle. If the brakes do not operate normally, adjust them by the following procedure.

CanadianBiker32

The DOT 3 is from my Auto storage area.

Would the Auto version of DOT 3 work ok for my Fat Bike bicycle hydraulic brakes?

cxwrench

Do you not pay attention to your own thread? It's been posted that DOT 3 is useable but not ideal. I recommend taking your bike to a shop w/ a reputable service dept and have them do it.

CanadianBiker32

ok thanks

Cyclist0108

If they are Avid brakes, the best way to deal with them is to put them in the trash can and install Shimano. Alvio would even be a major improvement.