On Monday, November 3, 2014 12:36:55 AM UTC-5, J Burns wrote:
On 11/2/14, 11:15 PM, wrote:
On Sun, 02 Nov 2014 22:55:46 -0500, J Burns
wrote:

On 11/2/14, 10:13 PM, wrote:
Your collapsed lined had nothing to do with clamping. Lines fail -
and the failure you mention is COMMON.. Clamping the lines WORKS, and
if done with the proper clamp it will not damage a good hose. Might
damage one that is already failing - which needs replacement
regardless.

I wish I understood what happened with that car. At first, I assumed
that the piston was jammed with dirt or corrosion.

If the line had collapsed, I would have expected pressure from the brake
pedal to open it so I'd get full braking on that wheel.

As I haven't seen it on any other vehicle, might those lines (just the
front) have been manufactured differently from most lines?

The other explanation is that something had been done to those lines
that isn't done to most lines. For example, I have read that if you
remove the caliper, you should be careful not to turn it 360 degrees (1
turn in the line) when you refasten it; a twist could cause the line to
burst later on.


Several things can happen. THe "lining" of the hose can separate from
the structural part of the hose and cause a "flap" that allows fluid
out to the caliper, but does not allow the caliper to return. In this
case, the brake initially drags, causing a pull to that side while
driving, and more on initial braking. When the brake heats up and
fades, the pull can move to the other side on braking. Can really
throw a beginner mechanic for a loop!!! Sometimes the problem is rust
in the metal crimp fittings expanding and squeezing the hose,
restricting fluid flow. This can have the same results, or it can just
cause the one brake to apply more slowly, causing a pull to the
opposite side on initial application.

The hose can also bulge, causing a soft pedal.
Then, of course, the hose can split/leak.

Other brake problems include calipers sticking due to corrosion or
fluid contamination, brake caliper sliders sticking, drum brake cyls
seizing, adjusters seizing or breaking, and caliprs or cyls leaking .

Leaking cyls can cause the brake to grab, or to loose friction.

Leaking grease seals can contaminate brake surfaces as well - causing
either a grab or loss of friction.

In other words, leaking cyls, calipers, or grease seals can cause a
pull in either direction.

Disabling brakes one wheel at a time can quickly isolate where the
problem is by elimination.

Those two blocked lines are the only failures I remember. It was a
European car from the early 1970s. I may have found the cause:
corrosion at a fitting gradually squeezed the rubber lining together.
(Maybe the rear lines used a different kind of fitting.)
http://ecomodder.com/forum/showthread.php/internal-flexible-brake-line-failure-finally-happened-me-21019.html

Shop manuals always seem to say to hang a caliper by a wire so its
weight isn't on the line, but I've read that mechanics often let
calipers dangle on brake lines. Who's right?

The shop manual.

I know it's "common" to let 'em hang, but I don't like abusing hoses any more than I have to to get the job done.

I had a '71 Porsche 914 once, was working on it circa 1996ish. Probably still had the original hoses. When I replaced them I cut one open out of curiosity, the inside was swollen almost shut, so it may be normal for this to happen over years 'n' years of use.

Now my dad has a '73 chevy pickup that he still drives... I don't remember ever replacing the hoses on it... still drives fine, but were it mine I'd probably replace them and rebuild the hydraulics on principle. Just me...

nate