Mark Rand wrote:

On Thu, 25 Mar 2010 09:52:01 -0700, Larry Jaques
wrote:

On Wed, 24 Mar 2010 17:32:39 -0500, the infamous "Karl Townsend"
scrawled the following:

I bought a brake controller that uses a sensor in the brake line. Today, I
took the brake line apart at the master cylinder, installed the "T" and
sensor. Had my better half pump the brakes while I bled. No big deal, I
thought.

Well, as soon as I started the truck, the brake warning light came on. So I
had the better half pump the brakes while I bled a whole can through the
front wheels. No joy.

I called "the Kid". He said to get a vacuum device from bumper bumper for
only $20. Well, it was $50. But I got it and bled a can through each front
wheel. No sign of bubbles at all. Note: the sensor is on the front set on
the tandem brakes

Still no joy. I got a brake warning light. I just got ****ed and called it a
day. What do I do tomorrow?

When you bled the rear brakes, the sensor piston went forward and hit
the alarm. Then when you bled the fronts, the piston went backwards
and triggered the alarm. You need to center the piston so the alarm is
not set.

In the olden days, I'd quickly open and close the bleeder screw to do
that. It was hit or miss. I believe that some sensors come with a
centering hole which you can insert a tool, but I got out of the
industry back in '86, before a lot of anti-brake hardware and
electronics were installed. Consult your local dealer for that info,
or buy the service manuals for your particular vehicle, Karl. You'll
want it anyway.

I'm confused here. Why do you lot have two axle vehicles with the brakes split
front/rear? Why aren't they split diagonally?

How do you control a vehicle, braking in a corner, if you've lost either the
front or rear anchors?

Expired minds need to know...

They experimented with diagonal split brake systems and found them to be
pointless. Having a single brake line to the rear also saves probably $5
per vehicle in manufacturing cost. The frequency of loosing half your
braking system while driving at any speed is also incredibly low. Much
higher probability that if a line is going to fail, it will do so on the
first actuation of the day, likely when you step on the brake initially
when releasing the mechanical parking brake. Even then, ruptured brake
lines are quite rare and a pinhole leak usually appears and is detected
first.