youcan use vacuum at the nipple or pressurize the M/C or have a helper work the wrench and bleed by instructing them to close when pedal is near down and open after returnign to the top.. or the trick with the bottle and a hunk of hose running into the bottle from the bleeded can work. then just crack the nipple open a tiny bit.


I prefer having a helper if available to press the pedal while I do the wrenching.

if a car has piston type cylinders or with an older master you can be pumping the brakes while bleeding and that can move the pistons past their normal movement pattern and into a zone that may be dirty.. If it is a new M/C that's not an issue and the calipers don't move far once they are seated. If you use a vaccum or pressure then sometimes you can avoid moving the rubber piston seals further than they are "used to" Occasionally that introduces a problem of a leak , because the rubber goes into a part of they cylinder that may have some accumulations of rust or debris in that "normally" unused portion of the bore.

in other words you can put your foot to the floor when bleeding but in a normally running car that would never be possible so that means the piston is moving to a position where it's not used to going.. If it's new than the bore should be clean and fine..

if a mechanic were to bleed your brakes in a used or old system.. and that could result in a leak and then you might turn and think well it didn't leak before he bled them. Next the customer may expect the mechanic to pay for the extra cost of new cylinders, arguing it wasn't broken before and he was only asked to perform bleeding. the problem may be avoided by using vacuum or pressure in this way, instead of making the master cylinder go to a "pedal to the floor condition"

I sometimes use a small vacuum generator to make suction from my comressed air, its mounted on a pressure cooker pot which contains vacuum and pulls the fluid into he pressure pot ( which contains vacuum) some use a rig to pressurize the master with a special cap. in this way I don't need a helper. vacuum generators are not expensive and have no moving parts, Its just basically a venturi device. they are a bit loud.