Date: Wed, 24 Mar 2004 21:33:51 -0500 (Eastern Standard Time)
From: "Dan Nees" <cookiedan@domain.elided>
Subject: [ihc] Master Cylinder
I had to replace the Master Cylinder on my Scout this week. I wanted to
get the cylinder I had on Ugly, NAPA part 1494R, which has large, larger
than normal, reservoir, but the store I was at could only get a NEW one at
$60something dollars. Since I couldn't afford that at the time, I went with
the stock Scout one Wagner PN # A1B 10-1339, $16.25.
The parts store guy steered me away from buying a Universal Bleed kit to
bleed the MC. He said that the prefered method now was to insert these
plastic block-off caps and let the system gravity bleed, with an ocassional
push on the piston. He also said that gravity bleeding was the prefered
method for doing all the brake lines now.
I've ben gravity bleeding my brake lines for years, but; have not done
the MC that way. It seems to have worked, but; I wonder what others thoughts
on the issue were.
I'm having a difficult time imagining a full 'bench bleed' purge of all air
from the m/c this way, and *any* entrained air in the m/c is your enemy. I
have a pair of brake hard lines that live in the special tool drawer, bent
to go up and over into the reservoirs below fluid level. Makes bench
bleeding fairly painless, then the plastic plugs seal the m/c ports until
the real brake lines are installed. That and a low pressure pressure
bleeder does a pretty slick job. Take a piece of AL plate about 3/8" thick,
just big enough to cover both m/c reservoirs. Drill and tap NPT on one
side, pipe fittings to a small(cheap) air regulator w/gauge and air quick
connect. Glue a chunk of 1/8" or so thick rubber to the underside with a
hole for air input. I use a bar clamp to hold it on the m/c. Plug up the
air and dial in about 5psi. Enough to move fluid, not enough(IME so far) to
trip the pressure differential switch/valve. Work the bleeder screws, and
just make sure to keep fluid in the reservoir. Flip the bleeder 180 deg. to
do the other reservoir. *So* much easier than screwing around with a vacuum
bleeder!