What happens if I get air in the master cylinder?

[dstrout]

I would like to take all 4 calipers off the car for 24-36 hours so that I can paint them correctly (i.e. steel brush + G2 two-part paint). Of course, if I do that, all the brake fluid is going to run out. Which is fine, since I was planning on flushing the brakes and re-filling with RBF600.

My question is, what happens when all the fluid runs out of the master cylinder? Does that just mean I have a lot more air to bleed, or does something bad happen? And if something bad happens, how do I plug the brake lines while the calipers are off? (I have visions of golf-tees-in-the-vacuum-lines from days of old).

thanks,
Dave.

[OkieSnuffBox]

Nothing bad happens, it will just take longer to properly bleed.


Some will suggest pulling the master cylinder to do a bench bleed, but I find the extra hassle not worth it vs just having to bleed some more fluid through the system.


Also, I've never had much luck with gravity bleeding or using a pressure bleeder, I always use the 2-man method.

[murdoc]

condoms and rubberbands should be enough to counteract gravity if you're worried.

Or cut the fingers off some rubber gloves.

[OkieSnuffBox]

Meh, just let it drain, the fluid is already a few years old and wrapping up the ends isn't going to keep air from getting in.


I always plan on a complete flush/bleed if I'm cracking the lines.

[sirbobbinhood]

I just did this to my car, go to harbor freight and get their line clamps.
http://www.harborfreight.com/4-piece...set-65116.html

I had my calipers off overnight and there wasn't a drop of brake fluid on the ground in the morning. What color are you planning on painting your calipers? I went with red and used the VHT spray with a clear coat.

[dstrout]

Cool, thanks, all!

I'm going with the G2 2-part kit in red. The BRZ is black, so I think that red should look good. I want to get the calipers off so I can give them a good power washing followed by a steel brush before I apply the paint. Hopefully that will help with adhesion.

I have to find some Subaru caliper stickers somewhere as well. Should look nice.

[Poodles]

Any parts store carries caps to stop this from happening. You could also just clamp the rubber soft lines (also a normal procedure). This can't be done if you have braided lines though.


It's not the master that's the issue, it's the ABS unit, and it's NOT fun to bleed, so DON'T let it go dry.


If you want to flush, force new fluid through until it comes out. Don't drain.