Bench bleeding dual master cylinder procedure

[Jim S]

I have a new master cylinder to bench bleed.  It has a bleeder port on the small reservoir. How is that used? Will it only bleed that one, or will it bleed both the small and large resevoir. What is the recommended procedure?

[jccatwb]

I've never bench bled a master cylinder. Don't know why it is necessary or desirable .  Enlighten me. 

[Skip Lackie]

Not sure I'm qualified to answer your question, but the idea is to remove all air bubbles from the master cylinder before it's hooked up to the brake lines for further bleeding.  I don't remember being told to do that ~30 years ago --  so we didn't.  But I now do it automatically, especially when instructed to do so.

[slk1966]

On 1/29/2026 at 3:28 PM, Jim S said:

I have a new master cylinder to bench bleed.  It has a bleeder port on the small reservoir. How is that used? Will it only bleed that one, or will it bleed both the small and large reservoir. What is the recommended procedure?

https://www.wikihow.com/Bleed-a-Master-Cylinder

Here is a step by step instruction program that explains how to bleed a master cylinder and the entire brake system.

 

[Jim S]

17 hours ago, slk1966 said:

https://www.wikihow.com/Bleed-a-Master-Cylinder

Here is a step by step instruction program that explains how to bleed a master cylinder and the entire brake system.

 

Thank-you.  I got it done.