TheSamba.com :: View topic - Trying to bleed brakes with vacuum pump...NOTHING comes out

Sat Jun 09, 2018 5:30 pm

Out of three wheels that I tried with the vacuum pump, on two of them nothing came out. It creates and holds vacuum, but not a drop. What does it mean? Can the bleed valve itself be clogged? Before I did this, the brakes worked fine. I plan to replace the rubber hoses, but I wanted to empty the system first. What should I do? Thanks in advance.

Sat Jun 09, 2018 6:04 pm

Some guys get the vac pump bleeding method to work but I have found it is a better use of time to buy or make a pressure bleeder, and put a head pressure on the reservoir.
I can't say from experience on why the brake fluid won't come out but you are most likely looking at weak rubber flex hoses, or maybe a plugged vent cap on the reservoir.

Sat Jun 09, 2018 6:06 pm

pull the bleeders and clean the tiny little holes out... if that does not do it.. then i would suspect brake hoses are collapsing on the inside

Sat Jun 09, 2018 8:28 pm

^^^^This & the first time you vacuum or gravity bleed,
it's step 1: pull bleeders, wrap teflon tape around the threads, CCW
so the teflon draws into the thread as you spin the bleeder back on.
The only difficult part is tearing the teflon tape down instead of using
full width, you only need 3 or 4 complete wraps to have enough to achieve
an air-tight seal.
EDIT: more, use the upper bleeds on your front calipers, bottoms are useless
to chase air out, for obvious reason.

Sat Jun 09, 2018 9:30 pm

Don’t use Teflon on the bleeder screws. The threads do not seal, the seat of the screw is the sealing area.

Sat Jun 09, 2018 10:15 pm

timvw7476 wrote: ^^^^This & the first time you vacuum or gravity bleed,
it's step 1: pull bleeders, wrap teflon tape around the threads, CCW
so the teflon draws into the thread as you spin the bleeder back on.
The only difficult part is tearing the teflon tape down instead of using
full width, you only need 3 or 4 complete wraps to have enough to achieve
an air-tight seal.
EDIT: more, use the upper bleeds on your front calipers, bottoms are useless
to chase air out, for obvious reason.

^^^^^ what they say. Sometimes you need to remove the bleeder and clean the passage in the caliper.
Theyj do suggest putting teflon on the threads of the bleader valves when vacuum bleeding. Your not sealing brake fluid you are stopping the threads from creating a vacuum leak and sucking air.
When vacuum bleeding, you need to start at the closest wheel to the master cylinder and work your way to the furthest wheel.

Good luck
Tcash

Sat Jun 09, 2018 10:19 pm

Keeping the caps on the bleed screws stops or lessens the problems they can give, both being clogged and being stuck. Teflon tape or paste on the threads will also reduce the likelihood of a bleeder being stuck.

Sat Jun 09, 2018 11:00 pm

just meant to use teflon tape as blocking material to block 'pirate air'
from spoiling a good brake bleed /gravity bleed, otherwise you'll go nuts,
& still have air hiding in the brake lines waiting to scare you witless once
you go back out in traffic. Never fun.

Sat Jun 09, 2018 11:10 pm

I see what you meant with the tape - I missed that you were talking about using it while bleeding. Was going to say if the threads are leaking there are bigger problems!!

Sun Jun 10, 2018 7:23 am

I've tried vacuum bleeding a few times and never had great results. I use the pressure bleed method now. I made a adaptor using a brake fluid battle cap. I feed the reservoir 10-15 psi from my compressor. It's faster and better than pumping the pedal method.