Stuck rear calipers

[Brett Dikeman]

At 10:52 AM -0400 10/11/02, Jagernauth, Stephen, RTLSL wrote:

>I'm replacing rear rotors/pads since they are down to minimum.  I'm
>changing fluid and fixing stuck e-brake cable/rusted shaft
>as well.   (Just got done with suspension bushings).

Make sure the cables have free play as well.  Also, if wear is
inconsistent between the two pads or from the inside edge versus
outside edge, check the guide pins, they're probably notched and
binding.  If the pins are visibly bent or notched, the entire carrier
must be replaced($$), the pins are not available separately.

I was able to spin each pin and using metal sandpaper, 'sand' out the
notch and then polish them to a mirror.  I used 300 grit paper inside
the guide pin holes to take out any burrs, then relubed everything
with Mobil 1 synthetic grease.  So far so good(6-9 months.)

>Pistons will not retract at all, I don't have a special tool to fit
>into the piston grooves.  15" Channel Lock is doing nothing.

They need to be SPUN IN(clockwise.)

>Caliper rebuild time?   I can take the calipers off and stick in the
>vise if that will help.

NO!  Do NOT force them in, you will damage the e-brake mechanism.

>   Do I need to crack bleeder valve to
>relieve pressure, never had to do that so I suspect calipers are
>really frozen.

I've seen a procedure which seems to have done Volvo listers a great service:
-clamp brake hose with a hose clamp or using pliers with adequate
protection(ie, doubled over piece of hose or similar to protect the
brake hose.)
-loosen bleeder
-screw caliper in

Why?  When you push the piston in, you push old fluid and all the
crap that's in the caliper back into the system, up into the ABS
unit, MC, etc.  It basically keeps the flow of fluid one-way.


>If I have to rebuild calipers, do I need special tool to get them
>out?  Home-brew solution?

    Needle nose vise grips work OK here(set the clamped-down width to
fit the two notches); there's also an official Audi tool($$) and a
"cube" adapter(different kinds of piston tabs on different faces of
the cube) that's not too expensive and available in many auto parts
stores...call around, ask for a brake piston tool.

Brett
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