Good Morning Raul,
On the mighty vac... I've had good success once I figured out a few
tricks...
If you PULL a vacuum you can bleed the front calipers pretty easily.
The disc brake seal works with both pressure and vacuum applied to it.
After you rebuild the front calipers keep tapping the side of the
caliper with a rubber mallet to loosen up all those air bubbles!
Had a heck of hard time with REAR brakes and the Clutch Slave cylinder.
Think of a cone shaped mushroom pushed into a cylinder. (Sorry, forgive
the mental image of that one!). As you apply pressure to the underside
of the cone... it presses out to the cylinder walls holding the pressure
in. If you apply a VACUUM to the underside of the cone... the cone
folds in allowing air to get past). So "vacuum bleeding" works, but on
some vehicles... what a pain. Yes, you need to wrap a little teflon tape
around the bleeder valves so air isn't sucked it. Since I wipe bleeders
with antisieze, that seems to work to. Clean and dry bleeders let air
get sucked past the threads, so you see a never ending stream of air
bubbles.
There is a neat "pressure pot" kit that I remember seeing. Basically has
a reservoir of brake fluid. Coupler attaches to the brake master
cylinder (remove the fill cap, and put this over it). Viola the whole
system is pressurized. Pressure is supplied by a spare tire (lots of
air, lower than 30 psi for safety). Whey you crack open a bleeder...
good stream of brake fluid.
Aircraft have tricks to "pressurize" the bleeder... forcing air back up
to the master cylinder. I tried it, and it worked. Only problem was all
the excess fluid spilling over the sides of the master cylinder (Messy
clean up!). I've since obtained a surplus medical vacuum pump and
collection jar system... so need to try that experiment again!
I found another trick.... siphon bleeding. Not sure why, but I seem to
be the only person with good success. A little anti-sieze on the bleeder
threads. Put the plastic tube TIGHT over the bleeder, then loop up and
over a higher point. As fluid goes up the tube it lets air bubbles rise
and keeps the cylinder full of brake fluid. Tube goes down into a empty
container to collect the old fluid (hazardous waste... I drop off at the
annual hazmat collection site). With the tube attached, crack open the
bleeder, tube looped up high, I just go pump the brake pedal! Refill the
master as needed, then go CLOSE the bleeder, then remove the tube.
Simple, easy, no fuss.
I just "flush" the old brake fluid by using the simple tube trick. Trick
is to make sure you get a TIGHT fitting clear tube, and keep it "looped"
up high. Oh, also acts like a great siphon as I learned when I went for
lunch and failed to close a bleeder back down.
Whew.... yes, Double Roast Coffee... pitch black, and I'm a roll!
Tom
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