Possible to flush brake system on a 1989 3.2 Carrera without calipers attached?
 

Hi,

I have installed new stainless brake lines and new rotors and my calipers are off being restored at PMB in Utah. The hard brake lines that fit into the calipers are currently plugged with the caps from the bleeder valves on the calipers.

Can I flush my brake system without the calipers and bleeder valves attached? The brake pedal is currently 1/2 depressed to prevent all of the brake fluid coming out of the system.

I would like to do this so that when my calipers are back and reinstalled I am pushing only clean brake fluid through them when I bleed the system. However, I am not sure how to flush the system without bleeder valves on it and without getting a lot of air in the system.

I have a Motive pressure bleeder and four bleeder bottles, so can hook those up to all lines at once.

Thanks,
Jonathan

I guess if you rigged something up to insure the air does not go back into the lines when your release the pedal could work.

I would keep the pedal depressed and when the calipers are ready, attach and bleed the lines starting with RR.

Gravity works well. Pour fluid into the reservoir, fluid pours out of the brake lines. Suggest a container below to catch the fluid. For flushing, doesn't matter if air is introduced. Purpose is to force out debris and old fluid. Evacuate air during the bleeding operation.

Attached calipers allow controlled flow via the bleed screw. If desired, force fluid through system faster using air pressure via a Motiv tank (or equivalent).

Sherwood

+1, Don't worry about air at this point, you are just flushing the lines. Once the system is complete then bleed the air out as you normally would.

I'm no rocket scientist but it seems to me that brake fluid like water will take the path of least resistance and as such the brake fluid won't travel throughout the entire system flushing all the old fluid as you either pump the brake pedal or apply force from a pressure bleeder.

Just release the pedal and it will flow...
I like to never introduce air and keep the reservoir full.

If you use a different kind of colored fluid you will see how nice it works.

Path of least resistance, sure but what path would that be? There isn't that many paths in the system.

If you're doing a complete flush,don't forget to bleed the clutch slave cyl on top
of the gearbox otherwise you will still have dirty fluid in your system ...

Cheers !
Phil

Why would you want to do this twice. Just drain what you have out completely and when you put the new calipers on bleed with the Motive bleeder.

X2 just dump the fluid and start over when the new calipers arrive.

In my experience, it's not that hard to start from scratch. Just proceed slowly.

I would not let air in the system. It's one thing to bleed the calipers after you install them it's quite another to try to get the air out of all the lines, proportioning valve, and master cylinder. I'd favor waiting and doing it all at once. If you have to do it twice, the gravity method while keeping the reservoir full would be my choice.

-Andy