Gravity Bleeding

[Bgunner]

So I've heard of it but never have done it myself. Doesn't it leave some air in the system?

I just did my calipers and to get the majority of the air out of the new ones I pulled out the bleeders and screwed then back in once fluid started to poor out. I let some fluid come out the bleeder then tightened the bleeder till I had a neighbor help pump the pedal. I still got air out of the system when I blead them.

In your guys' experience what is the best way to gravity bleed to get the most air out?

 

[Curious Hound]

If I was going to gravity bleed brakes, I'd probably do it the way you outlined it. But I do enough brakes that I went ahead and bought a vacuum bleeder setup a few years ago. Money well spent, especially since I live alone. Haven't been able to train the dog to pump the pedal for me.

 

[bobbywalter]

depends specifically how your lines are set up, I tend to plunge low in the front with a steady rise when i reline the trucks.


and it works...okay ish with a non abs system in a truck where you can do that.

regardless your not getting the air out without a vacuum setup or two people and a tired leg....especially with an abs system.


best way if you dont have a pump is speed bleeders.

 

[alwaysFlOoReD]

I use a Mason jar, about 15' of clear hose to engine vacuum source, another 2' chunk of hose to bleeder, and both to the mason jar. (15' hose about 1/2" into lid, 2' hose thru lid to bottom of mason jar.). Make sure to keep fluid in master. It goes quick.
Engine running...

 

[BroncLander]

I have a brake bleeder hose with a one way valve on it. I poke it in a bottle, pump the brakes, and its done.
Always start with the farthest brake from the master cylinder and work towards it. 1 rear passenger, 2 rear drivers, 3 passenger front, 4 drivers front

 

[bobbywalter]

I use a Mason jar, about 15' of clear hose to engine vacuum source, another 2' chunk of hose to bleeder, and both to the mason jar. (15' hose about 1/2" into lid, 2' hose thru lid to bottom of mason jar.). Make sure to keep fluid in master. It goes quick.
Engine running...

i do that alot too

 

[RonD]

Gravity Bleeding for brakes or clutch assumes you are just changing calipers, wheel cylinders or slave, not hoses or Master

So you are not allowing fluid to leak out of the hose when its disconnected, as that allows air in while fluid leaks out
A bit of air is OK, as the weight of the fluid above it will push it back into caliper or wheel cylinder, once hose is reconnected and bleeder is opened

Clutch Masters have a fitting on the end of the hose, Quick disconnect, that closes a valve so can't leak or let air in so easy to gravity bleed the slave

When the brake pedal is up then the Master's reservoir is open to all the brake lines, fluid is free to flow "downhill" to any "open hose end", fluid flows downhill because of........wait for it.................Gravity, lol, sorry had to do it

Anyway the principle behind Gravity Bleeding is that a fluid will always run downhill if given a chance
But air likes to go to the top of a fluid, so we have discovered "anti-gravity" not really
Manufacturers put Bleeder Valves at the top of a caliper, wheel cylinder or slave, where air would collect
So if you open a bleeder any air will come out first and then the fluid once all the air is gone.
General speaking 20-30sec of partially open bleeder will clear all the air in a new caliper, wheel cylinder or slave.

After beeding all the replaced parts there should be no air in the system, if there is then you have let air into the lines and will need to power bleed or vacuum bleed

 

[bobbywalter]

Gravity Bleeding for brakes or clutch assumes you are just changing calipers, wheel cylinders or slave, not hoses or Master

So you are not allowing fluid to leak out of the hose when its disconnected, as that allows air in while fluid leaks out
A bit of air is OK, as the weight of the fluid above it will push it back into caliper or wheel cylinder, once hose is reconnected and bleeder is opened

Clutch Masters have a fitting on the end of the hose, Quick disconnect, that closes a valve so can't leak or let air in so easy to gravity bleed the slave

When the brake pedal is up then the Master's reservoir is open to all the brake lines, fluid is free to flow "downhill" to any "open hose end", fluid flows downhill because of........wait for it.................Gravity, lol, sorry had to do it

Anyway the principle behind Gravity Bleeding is that a fluid will always run downhill if given a chance
But air likes to go to the top of a fluid, so we have discovered "anti-gravity" not really
Manufacturers put Bleeder Valves at the top of a caliper, wheel cylinder or slave, where air would collect
So if you open a bleeder any air will come out first and then the fluid once all the air is gone.
General speaking 20-30sec of partially open bleeder will clear all the air in a new caliper, wheel cylinder or slave.

After beeding all the replaced parts there should be no air in the system, if there is then you have let air into the lines and will need to power bleed or vacuum bleed

for sure.

depending on system, when swapping calipers getting an air bubble trapped is easy to do on the earlier 4wabs setup. took a minute to figure it out. drivers side just sucks it in. the sla trucks i never really had any issues with though.

 

[mikkelstuff]

Having no help, I finally went with super bleeders for my '75 Ranchero. They work great. Just crack open and route with a hose to a catch can. Then depress the brake pedal. The one way valve prevents air from re-entering through the bleeder. Just have to watch the master cylinder fluid level.

 

[RonD]

Back in the old days when I was a kid and couldn't afford any new parts I had to rebuild everything
So I did my share of brake masters and figured out how they worked, wasn't magic anymore, lol
And the same for wheel cylinders, no such things as calipers in my world at that time, lol, drums all around

So I would have to pull off a wheel cylinder, hone it, put in new seals as needed and reassemble, so brake lines were disconnected for awhile

I found if I used a stick against the seat to press down brake pedal a bit that would close off the Master cylinders reservoir, kind like putting your finger over the end of a straw so fluid doesn't leak out
Really slowed down the leaking fluid and of course plug the hose as best you can, lol

Gravity bleeding got the air out usually

If it didn't I built a "power bleeder", well kind of
Block of wood with an air valve added, valve part removed, 2 C-clamps
Inner tube, yes the thing that used to be inside tires, lol
Would use a hand pump to pump up the inner tube to 5 or 6psi, not much
Then put a hose between the two
Power Bleeder............lol
Could usually do all 4 wheels without adding fluid or pumping up inner tube again

Mom was my "power bleeder" for awhile but told me to "figure something else out", so I guess she invented it
Like they say "Mother is the necessity of invention", or something like that

 

[tw205]

If I was going to gravity bleed brakes, I'd probably do it the way you outlined it. But I do enough brakes that I went ahead and bought a vacuum bleeder setup a few years ago. Money well spent, especially since I live alone. Haven't been able to train the dog to pump the pedal for me.

Have you tried putting blocks on the pedal so the poor dog can reach them.

 

[Uncle Gump]

I just did my rear brakes... wheel cylinders and a brake line.

All I did was gravity bleed the rear system. Pedal is rock solid... at the top.

 

[Ranger850]

When I worked at the brake shop, I learned from the mechanic that some cars like being bled by gravity and some like it forced. We had a vacuum bleeder but we actually force fed them with a seringe for best results.

 

[alwaysFlOoReD]

When I worked at the break shop, I learned from the mechanic that some cars like being bled by gravity and some like it forced. We had a vacuum bleeder but we actually force fed them with a seringe for best results.
View attachment 97083

So your forcing fluid back to the master?

 

[Ranger850]

So your forcing fluid back to the master?

Back? no. Forcing fluid from the reservoir , through the system to the calipers, just like when you push the pedal. I would put the rubber tip of the seringe into the reservoir, right on top of the hole that fluid goes down, and push fluid, from the seringe, to the calipers, until the mechanic said "STOP".