Assembly Line Brake Bleeding

[Ghoste]

An out of the blue question, but how are hydraulic brakes bled on a moving assembly line?

[c00nhunterjoe]

in todays world, machine pressure and electronics. Back in the day- gravity bled/vaccum the old fashioned way.

[John_Kunkel]

In the day I believe they pulled a vacuum on the system and then introduced the fluid. Same with the A/C and cooling system.

[Kern Dog]

Thank you. Would you elaborate a bit with some specifics?
I've wondered about this as well.

[Ghoste]

Yes please. 

[John_Kunkel]

I can't testify to the factory specifics, but I routinely charge A/C systems by pulling a vacuum on the system and opening the valve to a heated cylinder of refrigerant sitting on a scale. Vacuum will pull the proper weight of pressurized refrigerant into the system.

For the brakes and cooling system, an adapter on the radiator filler neck or MC will work the same. The key is VACUUM, i.e. absence of air. Some claim that the spring in the lower radiator hose is not there to prevent collapse during operation but to prevent collapse during vacuum fill. 

Only detriment to the brake fill theory is the drum brake wheel cylinder cups, I'd think they wouldn't hold much vacuum.