Re: ihc-digest V6 #681

[jlandry@domain.elided (John A. Landry)]

In Linda Tripp's secret telephone recording, Monica and "Rik DesJardin"
<rik@domain.elided> were heard saying...

>Does the idle change when you push down on the brake?  If it changes than
>the booster is has a problem.  If it doesn't change something else needs
>adjusted.  How does the brake pedal feel as your applying the brakes?


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TROUBLE SHOOTING POWER BRAKES

From Bendix Corporation - Courtesy of Eldon McFarling

BASIC TEST

1. ENGINE OFF.  Depress and release brake pedal several times to remove vacuum
from power section.

2. Depress pedal and hold with light pressure, 15 to 25 lbs., and start
engine.

3. If power section is operating, pedal will fall slightly and then hold.
Less pressure will be needed to hold pedal down.

4. IF POWER SECTION IS OPERATING - FOLLOW INSTRUCTIONS UNDER VACUUM LEAK TEST.

5. IF POWER SECTION IS NOT OPERATING - disconnect vacuum hose from power
section vacuum check valve.  Then, with ENGINE RUNNING, check vacuum supply
with a vacuum gauge.  There should be at least 14 inches of vacuum.

6. IF VACUUM SUPPLY IS BELOW 14 INCHES - replace or repair vacuum hose and
vacuum fittings.  Also, tune or repair engine as required.

7. IF VACUUM SUPPLY IS 14 INCHES OR MORE - power section is defective and
should be replaced.

8. When adequate vacuum supply is obtained, repeat basic test.

VACUUM LEAK TEST

1. Run engine to medium speed.  Release accelerator and turn ENGINE OFF.  This
builds up vacuum.

2. Wait 90 seconds and apply brakes.  Two or more applications should be power
assisted.

3. IF APPLICATIONS ARE NOT POWER ASSISTED - disconnect vacuum hose from intake
manifold or power section check valve, whichever is easier.  If disconnected
at check valve, attach a short length of hose to valve.

4. IF APPLICATIONS ARE POWER ASSISTED - there is no vacuum leak.  Do the
HYDRAULIC LEAK TEST.

5. Blow into hose attached to check valve.  If air passes through, valve it
defective.

6. IF CHECK VALVE IS DEFECTIVE - install new check valve and repeat VACUUM
LEAK TEST.

7. IF CHECK VALVE IS OK - power section is leaking and should be replaced.

HYDRAULIC LEAK TEST

1. Depress and release brake pedal several times.  Then hold pedal depressed
with medium pressure, 25 to 35 lbs.

2. IF PEDAL DOES NOT FALL AWAY - hydraulic system is not leaking.

3. IF PEDAL FALLS AWAY - hydraulic system is leaking.  Check for external
leakage at wheel cylinders, hydraulic lines and hoses.  If there is no
external leakage, there may be an internal leak (master cylinder cups).
Repair or replace parts needed to correct leak.

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John L.
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