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Massey Ferguson 6465, 6480, 6485 - Park Lock

MF 6400 Series Tractors Service and Repair

The Park Lock is a parking brake mechanism located above the GPA40 rear axle. It is designed to immobilise the tractor in complete safety. The Park Lock is easily controlled via a pushbutton located to the left of and below the steering wheel. This pushbutton enables the operator to select the Park Lock engaged position (A) or the disengaged position (B) while seated in the operator's seat. The Park Lock mainly comprises three parts: hydraulic part, electrical part, mechanical part.

Hydraulic part

The hydraulic part is located above the rear axle inside the Park Lock unit (7)/cover plate (20) assembly. It comprises: two "O" rings (12) and (13), piston (2), which is returned by a set of eight.

Belleville washers (14). The effect of the load exerted on the piston (2) by the Belleville washers may be cancelled by fully screwing the special hexagonal head screw (5). Cancelling the load exerted by the Belleville washers is useful if: it is necessary to disassemble the Park Lock, Hydraulic and/or electronic problem occurs, which hinders tractor mobility.

Electrical part

The electrical part comprises: two solenoid valves (21) and (22), two switches (18) and (19). The solenoid valves and switches are screwed onto the Park Lock unit (7) and the cover plate (20) respectively. They are managed by the MF 6465, 6480, 6485, 6490 tractor's electronic system and via the connectors.

Mechanical part

The mechanical part of the Park Lock uses the components and the operating principle which are an extension of the hand brake mechanism. Here is a reminder of the components used: Actuator lever, Discs, Intermediate plates, Mechanism.

Parts list: (1) Park Lock (2) Piston (3) Pin (4) Wedge (5) Special screw (manual disengagement) (6) "O" ring (7) Park Lock unit (8) Actuator lever (9) Screw (10) Push rod (11) Pushrod (12) "O" ring (13) "O" ring (14) Belleville washers (15) Screw (16) Cover plate (17) Screw (18) Switch (19) Switch (20) Cover plate (21) Solenoid valve (22) Solenoid valve (23) 17 or 21 bar union (24) Mecanindus pin (25) Circlip (26) Tie rod (27) Screw (28) Stud (29) Washer/nut (M) Hand brake mechanism

Massey Ferguson 6465, 6480, 6485, 6490 - Park Lock Operation

Engaged position: mechanical action

The movement of the piston (2) caused when the Belleville washers (14) are released forces the actuator lever (8) to tilt, compressing the hand brake discs splined in rotation with the pinion. The rear axle is then blocked and the tractor is immobilised.

Disengaged position: hydraulic action

In this configuration, the Park Lock mechanism receives a 17 or 21 bar oil supply via two different solenoid valves. The piston (2) then compresses the Belleville washers and releases the push rod (10), the mechanism (M) and the hand brake discs via the actuator lever (8) and the hand brake tie rod (26). One of the two solenoid valves secures the Park Lock disengaged position in the event of a fault. The principle consists of maintaining the oil chamber of the piston (2) under pressure by shutting off its return line. A switch screwed onto the cover plate (20) and a second switch located on the Park Lock unit (7) check the hand brake disc wear and operation of the Park-Lock respectively via indicator lights. Each electrical component is controlled by the tractor's electronic system.

MF 6465, 6480, 6485, 6490 - Manual disengagement and engagement of the Park Lock

Manual disengagement

If manual disengagement is necessary - The Park Lock must be disengaged manually: if the rear axle is to be removed for dismantling, to provide tractor mobility in the event of a failure on the 17 or 21 bar hydraulic system or a fault on the electronic management system.

Using the remote control (1) linked to the special screw (5) on the cover plate, manually disengage the Park Lock by fully screwing in the special screw (5) until it no longer turns.

Description of the mechanical reaction during manual disengagement - When the special screw (5) is screwed in, the wedge (4) moves. This beveled wedge mechanically pulls the piston (2) upwards, compressing the set of Belleville washers (14). The load which had been applied to the push rod (10) is cancelled. The mechanism (M) and the hand brake discs are then released to make the tractor mobile.

Manual engagement

If for whatever reason the Park Lock has been disengaged, using the remote control (1), completely unscrew the special screw (5) until it comes into contact with a "hard" point. This procedure restores the Park Lock original functions: disengagement (hydraulic function) and engagement (mechanical function).

Massey Ferguson 6465, 6480, 6485, 6490 - Removing and install the Park Lock unit

Remove the components restricting access to the Park Lock unit.

Disconnect the connectors (TR5) to (TR8) connected to the switches (18) and (19) and the solenoid valves (21) and (22), marking them beforehand. Disconnect the 17 or 21 bar supply pipe connected to the union (23). Manually disengage the Park Lock.

Removal

Remove the M12 screws (27) and the nut (29) (if fitted) but not the M10 screws (15). Separate and remove the Park Lock from the centre housing. Recover the push rod (10) without allowing it to fall inside the centre housing.

Install

Clean the mating face of the Park Lock on the centre housing and on the unit (7). Smear the bottom end of the push rod (10) with Molykote type grease or equivalent. Reinstall this rod into it compartment on the actuator lever (8). Replace the two "O" rings providing the seal between the Park Lock unit (7) and the centre housing. Smear the housing of the piston (2) with Molykote type grease or equivalent. Position and refit the Park Lock, fitting the upper end of the push rod (10) into the compartment on the piston (2). Lightly smear the thread of the screws (27) and the thread of the nut (29) (if fitted) with Loctite 542 or equivalent. The thread of the screws and the stud (28) (if removed) must be smeared with Loctite as their ends protrude inside the centre housing. Tighten the screws (27) and the nut (29) to 100 to 130 Nm.

Reinstall the components which were taken off for hindering the removal of the Park Lock unit. Restore the original functions to the Park Lock (disengagement and engagement) by completely unscrewing the special screw (5). Reconnect the 17 or 21 bar supply pipe connected to the union (23). Reconnect the connectors (TR5) to (TR8) to the switches (18) and (19) and the solenoid valves (21) and (22). Start the tractor engine.

Slowly move the tractor several meters over a track with a slight slope and immediately place the shuttle lever back in the neutral position. Before stopping the tractor, push the pushbutton to engage the Park-Lock and carry out an initial test. When engaging the Park Lock, check that the tractor is immobilized by noting a slight hesitation caused by the transmission locking. Repeat the above procedure several times to confirm that the Park Lock is operating correctly. While seated in the operator's seat, move the tractor onto a track with a steeper slope. Stop the engine and check: efficiency of the Park Lock, that the hand brake is operating correctly. Check that there are no leaks in the hydraulic system (union, mating face, switches and solenoid valves).

Massey Ferguson 6465, 6480, 6485, 6490 - Disassembling and reassembling the Park Lock unit

Remove the Park Lock comprising the unit (7) and the cover plate (20). Unscrew and remove: solenoid valves (21) and (22), switches (18) and (19) fitted with their seal.

These switches are located on the cover plate (20) and on the unit (7) respectively. Recover the pushrod (11). The pushrod (11) acts as a transmission component between the switch (19) and the piston (2).

Park Lock unit disassembly

Completely unscrew the special screw (5) so that the Park Lock is in the manual and as a result, the Belleville washers (14) are almost released. Unscrew the screws (17). Release and remove the cover plate (16). Remove the circlip (25) and the pin (3).

Place the Park Lock in a press, protecting the underside of the unit (7) using two pieces of flexible protection (P). Also slide a flexible protection (P) over the cover plate (20). Apply the hydraulic press ram to the flexible protection (P) without exerting any force (F) on the cover plate (20). Unscrew the screws (15). Slowly decompress the hydraulic press ram to decompress the Belleville washers (14). Remove: cover plate (20), Belleville washers (14), first noting their number and positioning The eight Belleville washers are referenced in the spare parts catalogue in the form of a kit.

On the cover plate (20): Drive out the spring pins (24). Completely unscrew the special screw (5). Recover the wedge (4). Remove the "O" ring (6) and discard it

Take out the piston (2) from the Park Lock unit (7). Remove and discard the "O" rings (12) (13).

Park Lock unit reassembly

Clean: mating faces of the Park Lock unit (7); all parts. Using a jet of compressed air or a flexible iron wire, check that the hydraulic channels of the Park Lock unit (7) are not blocked. Check: that the pushrod (11) for the switch (19) moves freely in its housing; that there is a rivet fitted to the outer end of each hydraulic channel of the Park Lock unit (7). Temporarily remove the seals (12) and (13) from the piston (2). Test fit the latter inside the Park Lock unit (7). Check that the piston moves freely inside its bore with no "hard" points. Eliminate any impurities that may have become accidentally lodged inside the chamber of the piston (2). Lubricate the seals (12) and (13) with clean transmission oil. Install these seals into the grooves of the Park Lock unit (7). Hold the piston (2) above the Park Lock unit (7), positioning its flat section so that it is facing towards the return port.

Install the piston (2), gently tapping its centre in a circular motion using a plastic hammer. After fitting, check that there are no fragments of seal around the piston. Lightly smear the upper mating face of the Park-Lock unit with Loctite 5206 or equivalent. Reinstall the Belleville washers (14).

Install and position the cover plate (20) on the Park Lock unit (7). Test fit to check that the wedge (4) is correctly aligned with the clevis of the piston (2). If the alignment is incorrect, correct it.

Place the Park Lock in a press, using the same protections that were used for removal. Using the ram press, exert a moderate force (F) on the cover plate (20) so as to compress the Belleville washers. As soon as the cover plate (20) reaches the ParkLock unit (7), screw on and tighten the two screws (15) to 57-77 Nm. Lubricate the "O" ring (6). Install it into the groove of the cover plate (20). On the cover plate (20), screw on the special screw (5) and fit the wedge (4) at the same time. Form a wedge/special screw assembly using two new spring pins. Lightly smear the upper mating face of the cover plate (20) with Loctite 5206 or equivalent. Reinstall the cover plate (16). Tighten the screws (17) to a torque of 12 to 16 Nm. Ensure that each switch is fitted with a new seal.

Install: switch (18) onto the cover plate (20); pushrod (11) and the switch (19) to the ParkLock unit (7). Tighten the switches to a torque of 15-25 Nm. Install the solenoid valves (21) (22) in the same positions as before disassembly. Tighten the following onto the solenoid valve (22): spool to a torque of 18-20 Nm; solenoid to a torque of 4-5 Nm.

MF TRACTORS TROUBLESHOOTING
1652	1749	2620	2725	2805
3050	3120	3640	3709	4245
4455	5320	5455	5613	6150
6280	6480	6615	7618	7720