INSTALLATION INSTRUCTIONS FOR 680-1 MASTER CYLINDERS
Please read these instructions prior to installing your Grove 680-1 master cylinders as there
are critical steps that you must take to ensure proper operation of the brake system.
Removal of Existing Master Cylinders
1. Disconnect existing brake lines from the master cylinders and cap their ends to prevent
contaminants from entering.
2. Remove the ten screws holding the master cylinder components to the master cylinder
frame. Place rags, etc. under the master cylinder to collect the fluid that will drain out.
Prepare for Installation of Grove 680-1 Master Cylinders
1. Clean and inspect the master cylinder frame and pedals for cracks or any other cause for
replacement.
2. Inspect the existing brake lines for serviceability and capability. The existing master
cylinders produces only about 350 psi and the Grove 680-1 master cylinders are capable of
producing 1.000 psi. Ensure that the brake lines are of aircraft quality and are rated at
1,500 psi or more. If not, replace with suitable ones.
3. Determine whether your brake lines will attach to the rear or bottom of the Grove 680-1
master cylinders. Refer to Figure 1.
NOTE: You may attach your brake lines to either the rear or bottom of the
Grove 680-1 master cylinder. They are shipped with a plug in the lower
port for attachment of the brake lines to the rear port. If you wish to use
the bottom port, remove the plug from the bottom port and install it in the
rear port prior to installation. Use a sealing compound such as TiteSeal.
Never use Teflon tape!
Install the Grove 680-1 Master Cylinders in the Aircraft
1. IMPORTANT — Screw the shaft ball-end into the shaft as far as it will go.
2. Temporarily mount the master cylinder to the Scott housing using two of the supplied NAS
1352C08-8 using the supplied ball driver.
3. Unscrew the shaft ball-end from the shaft until you have approximately 0.020” gap between
the ball-end and the pedal socket.
NOTE: It is critically important that there is free-play between the ball-end
and the pedal socket. This free-play allows the internal shuttle valve to
open, allowing the brake to self adjust for wear and to vent the system for
thermal expansion. Refer to Figure 2.
4. Remove the master cylinder from the Scott housing and tighten the jam nut on the shaft.
5. Apply a coating of grease to the tip of the ball-end, then temporarily reinstall the master
cylinder using two NAS 1352C08-8 screws. Check to ensure that there is still approximately
0.020” free-play between the ball-end and the pedal socket. If not, remove and repeat this
process until you have the desired clearance.
6. Final attachment of the Grove 680-1 master cylinder using the nine NAS 1352C08-8 screws
and MS 3533-38 lock washers with the supplied ball driver.
7. Attach the brake line to the master cylinder.
Bleeding the Brakes
This is a two-step process. First remove the air from the system by bleeding from the bottom
up, then bleed the master cylinder to remove any remaining air in the master cylinder.
Grove master cylinders use Buna-N (Nitrile) O-Rings. For compatibility, use only MIL-H-5606
(MIL-PRF-5606) hydraulic fluid or its newer replacements: MIL-PRF 83282 or MILPRF-87257.
All of these fluids are miscible and can be used with each other
1. Remove the vent plug from the master cylinder reservoir. You should also place a rag under
the master cylinder to catch any spilled hydraulic fluid.
2. Connect a clean hydraulic pressure source such as a hydraulic hand pump to the bleeder
valve on the lower end of the brake caliper.
3. Open the bleeder valve one-half turn.
4. Pump hydraulic fluid into the system while observing the level in the master cylinder
reservoir. When the reservoir is nearly full, tighten the bleeder fitting and remove the
hydraulic pressure source.
5. Remove the protective cap from the bleeder valve on the master cylinder (refer to figure 1)
and crack open the bleeder valve using a ¼” wrench.
6. Depress the brake pedal by hand while watching for air bubbles to escape from the bleeder
valve. After a full stroke, tighten the bleeder valve BEFORE releasing the brake pedal.
Continue this process until the discharge from the bleeder valve is free from any air bubbles.
7. Fill the master cylinder reservoir with hydraulic fluid to approximately 3/8” from the top.
8. Replace the bleeder valve protective cover and master cylinder reservoir vent cap.
9. Apply foot pressure to each master cylinder and check for a “soft pedal” or any fluid leaks in
the system. If you experience a “soft pedal” repeat the bleeding process.
10. If you have also installed new brake linings, ensure that you follow the instructions for
seating new linings.