Question on bench bleeding master cylinder

[NovaJ]

I am going to be swapping to front disc brakes in the next day or two, and was wondering if when I bench bleed the new master cylinder, do I need to separate it from the vacuum booster? They were shipped to me already put together, and I didn't know if it would be ok to work the piston with the rod coming from the back of the booster, or if it was a better idea to take it apart.

Any help is appreciated. Thanks.

[ironhide]

In the booster is just a diaphram . The rod goes straight threw. Might be easier installed tho .

[Mike Holleman]

I am going to be swapping to front disc brakes in the next day or two, and was wondering if when I bench bleed the new master cylinder, do I need to separate it from the vacuum booster? They were shipped to me already put together, and I didn't know if it would be ok to work the piston with the rod coming from the back of the booster, or if it was a better idea to take it apart.

Any help is appreciated. Thanks.
The point of bench bleeding is to be able to fully stroke the master to be sure all air is removed. You can only know for sure this is taking place with the master seperated so you can manually stroke the piston until all air is removed. Put it in the vise.
Mike

[NovaJ]

Alright, I guess I will take the two apart. That is what I didn't know, is if the booster would limit the amount the master cylinder piston could easily travel.

Thanks for the info.

[ironhide]

Never thought of that . Just thought it was a time saver and if you don't that anyone to pump for ya .

[JRouche]

Is there a stop in a brake booster?? I didnt think there was. I think you dont have to split them. The rod will go all the way in. And really, even if there was a stop as long as you are able to push fluid thats all you need. You are only pushing the bubbles out. You dont need a full stroke.

But Im sure you can get a full stroke if you are curious. A booster is NOT meant to be an impediment for the braking system. Only a helper. There is still a solid connection for safety reasons. If the boaster fails you will still have brakes. Un-boosted, get your heavy foot out, but it wont stop the solid connection from the pedal to the rod. JR

[NovaJ]

Well now I am not sure what to do...guess I will just have to see how it goes once I actually start to get everything on and just go from there.

Thanks again for the help.

[MonzaRacer]

All the master cylinders I bleed I use my Phoenix Injector (www.brakebleeder.com) then with lines one turn open have helper push pedal down, hold, tighten lines, repeat. I was instructed about 20 plus years ago that the newer more compliant brake seals could fold over if you stoke master cylinders too far.and on bench bleeding we only stroked the piston about 1/4" to 3/8" and we used plugs(metal block off) in outlet ports. Saves fluid and bleeds faster too.