balance, thank yous

[Brett Dikeman]

At 7:44 PM -0700 4/11/02, Bernie Benz wrote:

>  > It's funny how things get out of whack but balance each other out.
>After reading this post, I don't understand what, in your opinion, is
>balancing out what.

The left rear caliper was dragging severely, causing 1mm wear over
and above the wear on the right side...and causing the car to pull to
the left, so when my alignment shop aligned it, they aligned it to
balance out this effect; they get it "right" using the machine, and
then road-test the car, then put it back on the rig and readjust.
When the left caliper was "fixed", now the car pulls to the right.

>  > It could be that I haven't driven the car in 2 weeks and have
>>  adjusted to the Volvo's neck-snapping brake pedal response, but the
>>  brakes seem too squishy; I did a complete pressure bleed this evening
>>  of the rear circuit
>No such thing as a complete brake bleed, of just half of the hydraulic
>circuit.

   Obviously doing just the rear circuit is not a compete bleed of the
entire system.  I said "a complete bleed OF THE REAR CIRCUIT",
meaning I completely bled the rear circuit(500ml of fluid or until
bubbles stop appearing, as per the Bentley), not "I did a complete
bleed of the hydraulic system, just the rear circuit."  It makes
little to no sense to bleed the front circuit since a)it was not
opened and b)I'm about to change the rotors on the front of the car
this weekend.

Stop nitpicking.


>  > I might also try doing the bleed with the drill bit on the
>>  proportioning valve to get more flow.
>For sure, an 1/8" hole through the proportioning valve will "get more flow",
>but what's this snake oil suggestion all about?

Volume two, Page 47.5
and
http://www.audifans.com/archives/1997/01/msg00368.html

The proportioning valve with the car up on a jack will restrict flow
to 20% of normal to the rear brakes, impeding a bleed of the rear
circuit.  Bentley doesn't outright suggest using the bit to fool the
valve when doing the bleed, but Igor lends his personal experience
that it helps, and he's highly respected on the list.


>I'm not a hi pressure bleeder but, when using atmospheric pressure bleeding,
>one certainly can draw air into the caliper on the master cylinder return
>stroke from around the loose bleed screw even with a tight plastic tube from
>bleed screw to sump.
>
>  To do it right one must open the bleed screw for the
>down stroke and close it prior to the return stroke.

...both of which are two reasons why people use pressure bleeders.


>   I find that atmospheric pressure bleeding usually works well
>without pumping, just takes a little longer.

List/world consensus is that pressure bleeding does a more complete
job(including all four mechanics I've regularly gone to, three of
which are audi master techs.)  Further, common list consensus is that
the clutch MUST be pressure bled(I'm not sure if the Bentley actually
specifically states this.)  Considering that it makes the job about
10 times easier in the first place, I haven't chosen to dispute it.


>  > Lastly, a huge thank you to all who responded over the last
>>  week/week+half to various "first serious brake job" questions(why I
>>  cc'd both lists, questions ended up on both.)
>IMO, yours apparently was a half brake job, not so serious.

It was "serious" in the regard that I completely tore down both rear
calipers save the ebrake mechanism, bead blasted/painted them along
with all the hardware+brackets, refinished the surface on both
pistons, resurfaced all 4 guide pins, cleaned out the carrier guide
pin holes+relubed, installed new rotors and pads.  It is the first
time I've done more than just change pads/rotors, and hence the
"first" part of "first serious brake job."

Further, my second sentence used the phrase "the complete rear brake
job" AND witness my mention of the fact that I have new front rotors
in hand.

Stop nitpicking.


>  > Certainly learned a lot(like, for example, ebrake cables get attached
>  > BEFORE you mash the brake pedal to get the calipers adjusted to the
>>pads/rotors.)
>More snake oil?  If the hand brake levers are against their stops the
>hydraulic system neither knows nor cares anything about the hand brake
>system.

"The hydraulic system" moves the piston out when you step on the
pedal to adjust the caliper to the new rotor/pads, and thus removing
the clearance necessary to turn the e-brake lever enough to get the
ball on the end of the cable into the hook on the lever.  If you undo
one carrier bolt, slide the caliper off the rotor/pads, cock the
lever back and install the cable, then go back to try and slide the
caliper over the pads+rotor, you'll find just exactly how the "self
adjusting" ebrake gets its name; the caliper won't slide over the
pads/rotors, and will need to be turned back in by about a eighth to
a quarter inch.

That's fine, except one piston took complete removal and benching
along with as much weight as I could put on it, and 30 minutes, to
screw back into the caliper.  The other one I was able to turn the
piston back in while it was still connected to the car(with some
difficulty.)

FYI, my definition of "constructive criticism" is not picking fights
on every little detail, labelling people's suggestions as "snake
oil"(particularly when in both cases, you didn't understand what I
was saying and should have asked for a clarification on those points,
instead of attacking them.)


Brett
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safety deserve neither liberty nor safety." - Ben Franklin
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