Bench bleeding a new/rebuilt brake master cylinder

[TitaniumTT]

Something about pressurizing a fluid that can strip paint kinda bothers me. What about the air-comp powered vac ones that pull fluid from the calipers?

[djmtsu]

Originally Posted by TitaniumTT

Something about pressurizing a fluid that can strip paint kinda bothers me. What about the air-comp powered vac ones that pull fluid from the calipers?

Meh, its only like 10psi to get it all done. I can usually get 2-3 calipers done before I have to pump it some more.

Another way is with a simple oil hand pump (think like what the Tin Man uses to stay lubed).

Fill it with brake fluid, attach a hose to the end, and then onto the bleeder. Pump it so there is fluid to the end of the hose, crack the bleeder and pump it up through the lines to air escapes at the MC.

I've done it that way too. Works great too.

[Pete_89T2]

Originally Posted by djmtsu

Meh, its only like 10psi to get it all done. I can usually get 2-3 calipers done before I have to pump it some more.

Another way is with a simple oil hand pump (think like what the Tin Man uses to stay lubed).

Fill it with brake fluid, attach a hose to the end, and then onto the bleeder. Pump it so there is fluid to the end of the hose, crack the bleeder and pump it up through the lines to air escapes at the MC.

I've done it that way too. Works great too.

I would advise against the oil hand pump method, which is essentially a "reverse" pressure bleed. Reason being much of the decomposed rubber, crud and brake system gremlin droppings tend to accumulate at the low spots in the calipers, and by reversing the flow you would be pushing that crud back into the system rather than bleeding it out along with the air. If you've done the "standard" pressure or vacuum bleed methods before, you'll notice that the fluid that comes out of the caliper bleeder screw initially is darker than the stuff coming out when you're about done with that wheel - the color is from all that crud.

[Pete_89T2]

Originally Posted by TitaniumTT

Something about pressurizing a fluid that can strip paint kinda bothers me. What about the air-comp powered vac ones that pull fluid from the calipers?

^ Which is why you need a really good seal between the cap & the MC. I had the same concerns until I tried it -- IMHO, pressure bleeding works SO much better and is faster than vacuum bleeding. I've used the Mityvac hand pump vacuum method before and won't be going back - I can get a rock hard pedal via pressure bleeding in a fraction of the time it took me with the Mityvac. And no sore hands from the repetitive hand pump action.

Pressure bleeding works very well with only 2~5 PSI pressure; just enough to push the air bubbles & fluid out the bleeder screws without risk of blowing any seals. So if you buy or build one for yourself, just make sure it has a gauge.