HomeMade brake bleeder idea?

[Ecomike]

It will eventually, as long as fluid remains in the reservoir. think about it. Once the fluid starts flowing down the line, where will the air come from? I don't like gravity bleeding because it's so slow, but it can be done. I still prefer vacuum. Just draw out at least as much fluid as your educated guess says is the capacity of the lines in question, and don't worry about the air coming past the threads.

IMHO, and based on 35 years of plumbing and hydraulic engineering and mechanics experience gravity bleeding to get rid of air pockets would be futile in most cases, especially with places that can trap air due to high spots in the plumbing route (Like a POS Prop-combo valve), and due to the small tubing diameter, and capillary forces involved.

That said I guess it can be an excellent way to drain and refill tubing that has no air trapped. If gravity could get rid of the air pockets, why bleed it all?

 

[Matthew Currie]

IMHO, and based on 35 years of plumbing and hydraulic engineering and mechanics experience gravity bleeding to get rid of air pockets would be futile in most cases, especially with places that can trap air due to high spots in the plumbing route (Like a POS Prop-combo valve), and due to the small tubing diameter, and capillary forces involved.

That said I guess it can be an excellent way to drain and refill tubing that has no air trapped. If gravity could get rid of the air pockets, why bleed it all?

I think the idea, at least in brake lines, is that the bubbles will not rise owing to the small diameter of the tubing and the viscosity of the fluid, but if you open the bleeder, gravity will eventually allow the fluid to push the air bubbles down. It can work, as long as there are no valves or other restrictions to free flow.

 

[Ecomike]

I think the idea, at least in brake lines, is that the bubbles will not rise owing to the small diameter of the tubing and the viscosity of the fluid, but if you open the bleeder, gravity will eventually allow the fluid to push the air bubbles down. It can work, as long as there are no valves or other restrictions to free flow.

Or the fluid will slowly leak around the outer surface of the air bubble and bleed liquid, leaving the air bubble in place. Thus the need for motive force to soundly push the bubble along. If I can't get the trapped air out with force using the brake peddle, by slamming the air bubble along with hundreds of pounds of force, what chance does gravity have of pushing an air bubble down that wants to rise do its density being less than the brake fluid density?

 

[Dobbs]

The best thing i have seen yet are speed bleaders around 10.00 per axle.Once installed just crack the bleader a little and pump the brakes check master cyl often after thru running a cyl of fulid thru just tighten back up I put a vac cap on mine so dirt and water wont get in and plug them.I installed them when I did the 95 up grade boster and master cyl.

 

[ehall]

I have those on the front but couldn't find any for the rear shoes

 

[Dobbs]

Got them from Orelliys .I havent had any ploblem useing them work grate.

 

[Matthew Currie]

Or the fluid will slowly leak around the outer surface of the air bubble and bleed liquid, leaving the air bubble in place. Thus the need for motive force to soundly push the bubble along. If I can't get the trapped air out with force using the brake peddle, by slamming the air bubble along with hundreds of pounds of force, what chance does gravity have of pushing an air bubble down that wants to rise do its density being less than the brake fluid density?

The air bubble doesn't go down because the system is closed. The fluid does not leak around the outer surface of the bubble, then, does it? If you open the system, it will indeed go down, but the only problem is that when you release the pedal it will pull it back up again, which is why pedal bleeding requires either a one-way valve at the open end, or a person with a wrench.

This is a pretty easy thing to see in action if you put a bubble in a piece of clear tubing and try to push it around. It will stay in the tube if the tube is closed, but if you add liquid at the top and open the bottom, the bubble will pass out the bottom eventually from gravity, and the fluid will fill the tube. It's just a lot slower and less satisfying with brakes, because the tubes are so narrow and long, and the fluid so viscous.