Repeat: '90 200qa brake problem

[Larry C Leung]

wouldn't the back of the MC be wet then?

LL - NY

On Sun, 02 Dec 2001 21:04:39 -0500 Kneale Brownson
<knotnook at traverse.com> writes:
>--
>If the pedal's going to the floor slowly and there's no leak it has to
>be
>the master cylinder seals letting fluid bypass doesn't it?
>
>
>At 01:26 AM 12/03/2001 +0000, scott miller wrote:
>
>>The brake problem:
>>I replaced the LR caliper, broke and repaired bleed screw in RR
>caliper,
>>allowed the reservior to empty in the process.  Refilled with
>Valvoline
>>Synpower, bled thoroughly.  After that, the brake pedal felt firm and
>tight
>>with no boost (engine off, bad bomb), but firm pressure sent it
>slowly to
>>the floor with boost (engine on).
>>
>>Replaced the master cylinder with new, not rebuilt.  Replaced rebuilt
>LR
>>caliper for slight leak in bleed screw.  Bench bled the MC, bled
>everything
>>thoroughly, gravity bled, pressure bled, pump bled all lines several
>times.
>>Tapped on all components while bleeding, removed calipers and tapped
>on them
>>while turning them and bleeding to get any trapped air (none).  The
>pedal
>>still feels initially firm, but drops with steady, firm pressure.
>There is
>>a light vibration during the pedal drop, feels like the hyd pump
>pushing the
>>booster (bad bomb).  The brakes seem to work well, the rears might
>be
>>contributing less, but it's hard to tell.  Turning off the ABS
>doesn't make
>>a difference.  No apparent loss of fluid, and no leaks I can find
>with
>>careful cleaning and inspection.  I suspect the new MC, which is
>under
>>warranty.  If not, I'd like to avoid long and expensive
>troubleshooting by
>>my local trusty, but expensive, mechanic.  He's already looked at it
>a
>>couple times, no luck yet.
>>
>>Any ideas welcome at this point, I'm stumped.  If someone out there
>has an
>>idea that prevents a big repair bill, my wife *might* let me keep
>it.
>>
>>Scott Miller
>>'90 200qa
>>Holland, MI
>>
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>>
>--
>