Vacuum pump

cbertozz

cbertozz

Hero member
Location
Australia
Hey I'd you use a vacum pump to bleed brakes: any tips on how to seal the connection - seems to pull in lots of air from somewhere judging by the bubbles coming through.
 
I had the same problem, there is a bleed nipple type or two that seal and stop air passing by.

See here: http://www.laverdaforum.com/forum/index.php/topic,86754.msg380018.html#msg380018
 
Absolutely no need for any further sealing.  It is NOT air from the outside that you see, google "cavitation".   

Don't make it more tedious than it is...  :D

piet
 
Always pulls some bubbles past the bleed nipple. Does not affect the bleeding. If you get solid pressure, the brakes work and they remain constant and not spongy then all OK.
 
If the bubbles annoy you because you're watching for clear fluid coming out of the system, put a bit of thread tape on the nipple. Might help prevent nipple seizure too. I hate having my nipples seized.
 
Thick silicone grease around the base of the bleed screw will greatly reduce the air sucked in from around the threads and opening the screw only slightly[if using an air or electric vacuum pump] will reduce the air drawn in. I've found that the tiny bubbles in the hose are from the nipple leakage[have fun with that guys] the real air usually shows as a gap in the fluid being drawn out.
 
I've been vacuum bleeding hydraulic brake lines for over 40 years. I use a sealed canister with a clear neoprene hose that fits over the bleed nipples and charge the canister with approx - 20 inches of vacuum from the intake manifold of a running engine and pinch the hose with small vice grips - Then always finish with a pedal pump test - Keep the master topped up during the procedure.
 
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