Should I drain the entire brake system?

[Hendog]

I plan on rebuilding my brake calipers tomorrow. I will also change the rubber brake lines, change bleeder valves with speed-bleeders, and bleed the clutch. Should I start with opening the bleeder valves and draining as much out as I can then do the work? Is there any reason why I would keep any of the old fluid in only to bleed it all out at the end? If I keep as much fluid in the sytem as I do the work, will this minimize the chance of getting air in the sytem when bleeding?

Your experiences are appreciated.

[IROC]

Don't drain it - just go about your upgrades and bleed the whole system whgen you're done. Like you suspect, this will mitigate the chances of getting any air in the system...

Mike

[Hendog]

Thanks Mike. Another persons' opinion helps those of us who haven't done these things before.

[BK911]

Use a different color brake fluid. That way you can see when you get all the old stuff out.

[jluetjen]

Whatever you do, don't drain the system dry because it's a real pain in the neck to refill the system. You'll need to bench-bleed the master cylinder if you do.

[911mot]

Open the front caliper bleed nipples and use a length of wood wedged against the seat to hold the brake pedal in the full down position. This will stop any fluid dripping out as you work on it and will minimise the amount of air you have to remove when bleeding. Attatch pipes to the bleed nipples or cover with large lumps of rag before you do this to avoid brake fluid spraying everywhere.

[Hendog]

What size tubing is required to fit over the bleed nipples?

[911mot]

Small rubber like vacuum hose. Route into a bottle. Leave hoses attatched until youve squeezed the pistons back.