very soft brakes after swapping parts

[vintage_car]

I put in a new clutch slave and master cyl. I also removed my brake master and booster from the car to do some welding. I got everything back together. Bled the brakes furthest point first up to the front, and then the clutch slave last. The car stops but it takes some time and the pedal moves very, very easily to the floor, but does come back up on its own. Any suggestions?

[02jake]

try adjusting the rear brakes then the hand brake. rebleed the system. I have had to do some cars with a reverse bleed. Using a siringe (spelling ?) open up the bleeder and push the fluid back into the master. Use as a last straw. Also bleed the master before bleeding entire system. Have someone step on the brake pedal and crack open the brake lines till no bubbles are present. Have fun.

[Zenon]

There's air in your brake master, probably. Use a pressure bleeder - all other methods are inferior. I've tried them all...

BTW, that reverse flushing idea is kinda scary - seems like a good way to inject dirt into the hydraulics. Maybe pulling a vacuum at the reservoir would help clear an air lock in the master, but I would not open any bleeders while under suction, either. Pressure bleeding has always worked for me so far, though.

I would normally also say check/adjust rear brakes but since it was apparently OK before the work and you didn't touch them, I doubt they are the problem. Anyway, here's my take on it:

http://www.zeebuck.com/bimmers/tech/rearbrakes.html

regards,

Zenon

[TobyB]

I've found that when you first put fluid in a new component,

there's quite a bit of air that won't bleed on the first try.

With front calipers, I give 'em a few gentle whacks with a hammer after the first bleed- it often dislodges a pretty big pocket of air. Then, inevitably, another bleed a few weeks later gets out some more...

I wouldn't whack a master cylinder, though... it sounds like one side of your cylinder has an air lock in it...

t

[Guest Anonymous]

I have a device called a topsider used to pull fluids. Can I hook this up and pull the fluid through? Also do I leave the brake resivoir open or keep it closed? When I pump the brakes I hear air sucking in andout and I wonder if that is the entire casue of the problem. I replaced the brake hoses that go from the resivoir and maybe they are not clamped tight enough.