Customer

This system was not an easy one to get the air out of. Poor design is my thought. It actually was bad enough for Ford to release a Technical Service Bulletin for it. Here is the bulletin to assist you in getting the pedal bac.

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UNRESPONSIVE CLUTCH: AIR ENTRAPPED IN HYDRAULIC SYS - Page 1 of 6

UNRESPONSIVE CLUTCH: AIR ENTRAPPED IN HYDRAULIC SYS

TECHNICAL SERVICE BULLETIN

Reference Number(s): 93-12-19, Date of Issue: June 9, 1993
Related Ref Number(s): 93-12-19

ARTICLE BEGINNING

CONDITIONS

CLUTCH - "SOFT" UNRESPONSIVE CLUTCH PEDAL - AIR ENTRAPPED IN
HYDRAULIC SYSTEM - SERVICE TIPS

CLUTCH - HYDRAULIC - UNABLE TO RELEASE - AIR ENTRAPPED IN SYSTEM -
SERVICE TIPS

CLUTCH - HYDRAULIC BLEED PROCEDURE - SERVICE TIPS

TRANSMISSION - M50D AND ZF LIGHT DUTY - GEAR CLASH - AIR ENTRAPPED
IN CLUTCH HYDRAULIC SYSTEM - SERVICE TIPS

APPLICATION

Model(s): FORD LIGHT TRUCK: 1993 AEROSTAR, BRONCO, EXPLORER, F-
150-350 SERIES, F-47, RANGER

Group: Transmission

Bulletin No.: 93-12-19

Date: June 9, 1993

ISSUE

A "soft" unresponsive clutch pedal may be felt or the driver may
be unable to release the clutch. This is caused by air entrapped
in the clutch hydraulic system.

ACTION

Use the information in this TSB article in addition to the
appropriate bleeding procedure. This article includes detail as
well as extra service tips for easier hydraulic clutch bleeding.

The clutch hydraulic system for the 1993 model year is new and
more difficult to bleed than the previous hydraulic system.
Therefore, a different bleeding procedure is required for these

vehicles.

RANGER, EXPLORER, AEROSTAR

The most difficult systems to bleed are on the Ranger, Explorer,
Aerostars.

NOTE: When installing dry clutch cylinder or tube service
parts, do the bench bleed procedure first.

BENCH BLEED

The compact vehicles are more difficult to bleed because the
downward angle of the master cylinder makes it difficult for air
to escape up into the reservoir. Therefore, if the master cylinder
is removed from the vehicle and bled while held in a vertical
orientation (a bench bleed) air can escape much more efficiently.
Refer to Fig. 1 .

BENCH BLEEDING PROCEDURE (CONCENTRIC SLAVE CYLINDER)

1.Remove master cylinder, line and reservoir from vehicle and
assemble with replacement parts required based on initial
concern.
2.Hold the master cylinder vertically with the reservoir feed
hose in the highest position on the body. See Fig. 1 .
3.Fill the reservoir and extend above the master cylinder and
assure the quick connect on the clutch line is below the
master cylinder. (Lightly clamp reservoir in a vise).
4.Using a small screwdriver, depress the internal mechanism of
the male quick connect coupling to open the valve. See Fig.
1 .
5.Stroke and hold master cylinder pushrod.
6.Close quick connect valve.
7.Release master cylinder pushrod.
8.Fill reservoir.
9.Repeat Steps 4 through 8 four more times.
10.With the master cylinder still being held with the outlet tube
and reservoir feed tube ends high, quick connect closed and
the reservoir full, proceed as follows:
a.Push the pushrod into the body several times quickly to
expel any remaining air.
b.If it is a remote reservoir, pinch the supply hose with
your fingers two or three times to help move air into
reservoir.
11.When the movement of the pushrod is .130" (4mm) or less when

stroked in Step 10, reinstall the master cylinder into the
vehicle and couple it to the slave cylinder.

Fig. 1: Out-of-Vehicle Bench Bleed Master Cylinder Orientation

ON VEHICLE BLEED PROCEDURE, CONCENTRIC SLAVE CYLINDER

Under normal conditions, disconnecting the clutch coupling will
not introduce air into the system. However, if there appears to be
air in the system (spongy pedal or insufficient bearing travel),
the system must be bled. See Fig. 2 . The following procedure is
used with the hydraulic system installed on the vehicle.

1.Disconnect the coupling at the transmission with a coupling
disconnect tool (T88T70522A) or equivalent by sliding the
white plastic sleeve toward the slave cylinder while applying
a slight tug on the clutch tube.
2.Clean dirt and grease from around the reservoir cap.
3.Remove cap and diaphragm and fill reservoir to the step with
Heavy Duty Brake Fluid (C6AZ-19542-AA or BA) (ESA-M6C25-A) or
equivalent.

CAUTION:Brake fluid must be certified to DOT 3
specification.

a.By hand, apply 10-15 lbs. to clutch pedal.
b.If pedal is hard (.25-.50 movement), skip to Step 9.
c.If pedal is spongy, proceed to the next step.
4.Using a small screwdriver ...
a.Depress the internal mechanism of the male coupling to
open the valve.
b.While continuing to hold the valve open, slowly depress
the clutch pedal to the floor and hold.
5.Remove the screwdriver from the coupling, closing the valve.
6.Release the clutch pedal.
7.Refill the reservoir to level at step.

NOTE: The reservoir must be kept full at all times to
ensure that there will be no additional
introduction of air into the system.

8.Repeat Steps 4 through 7.
9.Install cap on reservoir.
a.Reconnect the coupling to the slave cylinder.
b.Check that the connection is secure by applying a slight

tug to the clutch tube.
10.Stroke the clutch pedal as rapidly as possible for five to ten
strokes.
11.Wait one to three minutes.
12.Repeat Steps 10 and 11 three more times.
13.Loosen the bleed screw which is located in the slave cylinder
body next to the inlet connection.
14.Depress and hold the clutch pedal while tightening the bleed
screw 3-5 N-m (2.2-3.7 lb-ft).
15.Refill the reservoir to level at step.
16.The hydraulic system should now be fully bled and should
release the clutch. Check the clutch reserve.

Fig. 2: In-Vehicle Master Cylinder Installation

F-SERIES, BRONCO

Since full size vehicles have master cylinders which are mounted
in a level attitude, they bleed more efficiently than do compact
vehicles. However, some difficulties may still be encountered if
the new procedure is not used.

VEHICLES WITH CONCENTRIC SLAVE CYLINDERS

Use the same bleed procedure as specified for the compact vehicles
which is included in this article. The optional bench bleed
procedure may be used, but is probably not necessary.

VEHICLES WITH EXTERNAL SLAVE CYLINDERS

1.Clean reservoir cap and slave cylinder in area of the tube
connection.
2.Remove slave cylinder from the transmission bell housing.
3.Use a 3/32-inch diameter punch to drive out tube holding pin.
4.Remove the tube from the slave cylinder and place tube end
into a container for waste fluid.

NOTE: The tube is connected to the master cylinder, so
keep the reservoir cap tight to minimize fluid
loss.

5.Hold slave cylinder so connector port is at highest point, by
tipping cylinder to approximately 30 degrees. Fill with
approved DOT 3 brake fluid through connector port. See Fig.
3 .

NOTE: It may be necessary to "rock" slave cylinder around
or push gently on push rod to expel all the air.
Pushing on push rod too hard will cause fluid to
spray out of the connector hole.

NOTE: Do not allow any moisture or foreign matter to
enter slave with brake fluid.

6.When all the air is expelled from the slave cylinder and no
more bubbles come out of the port hole, install slave
cylinder.

Fig. 3: Filling Slave Cylinder

NOTE: Fluid is expelled from the connector port, as the
push rod is compressed attaching it to the
transmission and lever.

7.Gravity fill the master cylinder and tube as follows.
lRemove the reservoir cap and diaphragm.
lFluid should flow out the open end of the tube into waste
container. Be sure to keep the reservoir full.
lWhen fluid is flowing out in a steady uninterrupted flow
and fluid is level with step in reservoir, install cap and
diaphragm.
lInstall end of tube into slave cylinder.
lReplace pin holding tube to slave cylinder.
8.Remove the slave cylinder from the transmission.
9.Holding the cylinder so that the port for the tube is at the
highest point, slowly push the pushrod into the cylinder and
slowly let it return. Be sure the reservoir is full of fluid
beforehand. Repeat this step two more times.
10.Re-attach the slave cylinder to the transmission.
11.Rapidly depress the clutch pedal 10 times through a travel of
about 1" (26.4mm).
12.If the pedal is not hard within .25" (6.35mm) to .5" (12.7mm)
of travel, repeat Step d.
13.System should be bled and functioning properly.
lTo verify proper system function, set parking brake and
put vehicle in neutral.
lStart vehicle and shift into reverse gear.
lIf gears grind, other components may be causing the
concern.
lCheck slave cylinder push rod travel as described in this
section.

PARTS INFORMATION
Part Number Part Name Class
C6AZ-19542-AA Heavy Duty Brake Fluid B

Shawn