Using a pressurised brake bleeder

[Paul70]

Wondering whether to invest in a pressure bleeder and start bleeding my own brakes. The process looks straightforward but according to a recent Volkswizard video the VW manual states to start with the master cylinder reservoir, around the min level, rather than brim full, so quite a bit of air space. What happens to the air in the tube of the pressure bleeder and in the top of the reservoir when the fluid is pushed through? is there a risk of this getting pushed into the system, or is it simply a case of air always rises and the density of the fluid is greater? It feels like one of those obvious questions so apologies in advance if it is!

[madstaff]

It fills the master cylinder with fluid as soon as its pressurised.

[Paul70]

Thanks Madstaff - but what happens to the air that was in the reservoir when the fluid enter once it’s pressurised? It has to go somewhere?

Sorry if I am just being a little thick with this question.

[Tractor Dave]

The is a little pipe that feeds brake fluid to the bottom of the reservoir. I generally start with it half full. No risk of air getting in at all. A brilliant bit of kit but use carefully. Don't go too high pressure wise, especially in older cars as the reservoir can pop!

[sjw]

Wondering whether to invest in a pressure bleeder and start bleeding my own brakes. The process looks straightforward but according to a recent Volkswizard video the VW manual states to start with the master cylinder reservoir, around the min level, rather than brim full, so quite a bit of air space. What happens to the air in the tube of the pressure bleeder and in the top of the reservoir when the fluid is pushed through? is there a risk of this getting pushed into the system, or is it simply a case of air always rises and the density of the fluid is greater? It feels like one of those obvious questions so apologies in advance if it is!

I did it not long ago. The process is as simple as it looks, don't overthink it Just make sure you get the pressure high enough to bleed the ABS module

[Paul70]

Thanks SJW, that’s exactly what I wanted to hear. It’s a fluid flush so sticking with 15 to 20 PSI.

[Paul70]

Brake fluid changed on both mine and my daughter’s cars - very straightforward.