Brakes: Stude Avanti brake bleed time factor??

[Hawklover]

Assume that an Avanti is on a lift and that all four brake bleeder screws are cracked open.
How long should one expect it to take for all four lines to receive new fluid with continual replenishment of the dual master cylinder fluid?.........via gravity bleed.

Thanks in advance for your assistance.

[(S)]

Once it starts flowing clean, cap that one, and so on. Way better to use 2 people or a machine to 'push' more of the crud out with pumping of the pedal..

[Hawklover]

Yes I understand that, what I want to know is how long that will take, one hour, two hours half a day?

Once it starts flowing clean, cap that one, and so on. Way better to use 2 people or a machine to 'push' more of the crud out with pumping of the pedal..

[kxet]

We could bet on things like this, lottery anyone?

[Xcalibur]

Wow, what an inefficient way to do it. There are both pressure systems that attach to the master-cylinder that work quickly and well on Avantis, and vac systems that attach to each wheel cylinder, in turn. I've used both and find either will do the job. All the best.

[Jolly-John]

Yes, Xcalibur.....and Harbor Freight sells a very usable vacuum-style bleeder for under $25, if I recall correctly. As most of us may have learned back in the day: Start by bleeding the wheel cylinder farthest away from the master cylinder, and work down to the closest one.

Maybe Hawklover could background us about the "why" of his need to know. I'm simply curious....and certainly not criticizing him. John

[Mike Van Veghten]

Hawk -

I've left mine open a crack for a day or day+.
Does a decent job.
The difficult part is the tall "hump" at the rear cross member. That's why just a "crack" open so it fills that part of the tubing.

Mike

[bezhawk]

Gravity bleeding can take a long time. Any air displaced has to travel up the tubing all the way back to the master cylinder, and out the tiny compensation port. A very little will be let out the bleed screw. Fluid dynamics of a tube and all that. It is not the same as pressure bleeding pushing the air out.
Take a straw, fluid will not flow out of it until the air bubble has traveled back to the source. (unless pressure forces the bubble out). But that would be pressure bleeding wouldn't it.

[Colgate Studebaker]

My question to Hawklover is if the Avanti has a stock system (front disc and drum rear with the single master) or a modified system (e.g. dual master with Turner fronts and possibly 4 wheel disc)? My experience has been that drum brakes do not "self bleed" very well and getting pressure to push out the air is necessary. Disc brakes will self bleed but 4 wheel can be challenging. As others have said either applying pressure or vacuum has been the most efficient way that I have bled brake systems. To each his own, this is my two cents worth. Hope it helps, Bill.

[WCP]

My experience with gravity bleeding is approximately 15 min. per wheel cylinder. By bleeding through clear tubing into a proper glass bleed bottle (easily fabricated), you will be able to see a colour change as the new fluid comes through the tubing and settles in the bottle. You will gradually see a demarkation in the bleed bottle between new and old fluid. I use a 32 oz. pickle jar. The fluid in the line should be free of bubbles during this process. Adjust the opening of the bleed screw so no air leakage occurs at the connection. The 15 min. will pass quickly as you will have to ensue the master cylinder is kept topped-up. I use a piece of plate glass to lay on top of the M/C during the process. I have found this process the only way to bleed Dot 5 fluid as the Dot 5 fluid tends to foam under pressure or vacuum. Vacuum bleeding also tends to draw air into the bleed line at the bleeder screw and connection. BTW, Ive been using Dot 5 in non-ABS vehicles since the 80's.

[Hawklover]

John some information for you is in order:-) Any work done on my Avanti has to be done at my buds shop, when he can fit me in LOL..this old spine and other health related aspects preclude me from doing so much of my "own wrenching" Ok that being said.....I already know the horror of having the brakes bled in my Avanti due to "well meaning" mechanics not properly covering the inner fender area and front fender....yes...dot3 damage on the painted surfaces.....it has been four years since I had a two chamber master put on the car....and recently considered flushing out all the fluid (I have however sucked out the fluid from the master with a turkey baster two times over the past four years)..to bleed out the brakes I have to put the car on a lift...one tech is on a 15 foot ladder checking the master levels as the tech on the ground is opening and closing the bleed screws...yours truly will be sitting in the car working the brake pedal..I just have a fear that dot 3 will once again find its way to various painted surfaces....although this time I will put many layers of rags under the brake booster to protect those surfaces.....I thought that I could do away with all of that and just leave the car on the lift for an hour or so with the bleeder screws open and continual checking of the master cylinder levels? In the end I may have to go to another shop I know of that works on classic autos exclusively...better to actually pay for this to be done, than to go to my friends shop where the work would be for free but the 'pain" of damage will not be a pleasant thought.

Yes, Xcalibur.....and Harbor Freight sells a very usable vacuum-style bleeder for under $25, if I recall correctly. As most of us may have learned back in the day: Start by bleeding the wheel cylinder farthest away from the master cylinder, and work down to the closest one.

Maybe Hawklover could background us about the "why" of his need to know. I'm simply curious....and certainly not criticizing him. John

[Hawklover]

Brad thank you for the insight.....I will have to do this the correct way come the spring.

Gravity bleeding can take a long time. Any air displaced has to travel up the tubing all the way back to the master cylinder, and out the tiny compensation port. A very little will be let out the bleed screw. Fluid dynamics of a tube and all that. It is not the same as pressure bleeding pushing the air out.
Take a straw, fluid will not flow out of it until the air bubble has traveled back to the source. (unless pressure forces the bubble out). But that would be pressure bleeding wouldn't it.

[Hawklover]

Appreciate the insight!

My experience with gravity bleeding is approximately 15 min. per wheel cylinder. By bleeding through clear tubing into a proper glass bleed bottle (easily fabricated), you will be able to see a colour change as the new fluid comes through the tubing and settles in the bottle. You will gradually see a demarkation in the bleed bottle between new and old fluid. I use a 32 oz. pickle jar. The fluid in the line should be free of bubbles during this process. Adjust the opening of the bleed screw so no air leakage occurs at the connection. The 15 min. will pass quickly as you will have to ensue the master cylinder is kept topped-up. I use a piece of plate glass to lay on top of the M/C during the process. I have found this process the only way to bleed Dot 5 fluid as the Dot 5 fluid tends to foam under pressure or vacuum. Vacuum bleeding also tends to draw air into the bleed line at the bleeder screw and connection. BTW, Ive been using Dot 5 in non-ABS vehicles since the 80's.

[jif988]

There's an easier way to bleed brakes that I have done many times....you just need a turkey baster and a short piece of rubber or plastic hose that will fit snugly over the bleeder screw. Starting at the furthest wheel from the master cylinder, fill your baster up with fluid, attach to the bleeder screw via the rubber hose, crack the bleeder screw open a half turn or less, and "inject" fluid until you see it filling up the master cylinder. Close the bleeder screw, go to the master cylinder and suck out the fluid and discard it. Repeat on the other three wheels and you are done. This way, you are "pushing" any trapped air out the master cylinder. The air will thank you because now it will be reunited with all the other air!

[WCP]

Re post #14 / I don't think that is a good approach. Reversing the flow will result in wheel cylinder crud "falling out" into the lines and "dead zones", particularly in the firewall mounted master cylinder. That's a bit like trying to push sewage flow up hill in a septic system IMHO.