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Massey Ferguson 7499, 7495 load sending auxiliary mechanical spool valves

MF 7400-7700 Series Tractors Repair Operations

Massey Ferguson 7495, 7499 tractor proportional auxiliary spool valves, of the Bosch/Rexroth SB23 LS type, are fitted to the high flow rate high pressure circuit.

They are fed by the oil coming from the priority block(s). When no functions are being activated, the entire flow rate is directed towards the spool valves.

If certain priority functions are being supplied, the remaining flow is then available for the auxiliary spool valves. E

ach spool valve has a flow regulating system controlled by a black, red, green or yellow button located directly on the each spool valve regulating valve system.

The main spool of the valve is controlled by a cable linked to a lever in the cab. The spool directs oil towards either outlet port.

Each outlet port is linked to the LS pilot line of the variable displacement pump regulating valve via the priority block(s).

The auxiliary spool valves are made up of elements themselves containing spools and valves. Some elements cannot be identified as spare parts.

Different types of MF 7499, 7495 spool valve block components

A spool valve block can consist of three, four or five of the following components. It can combine components of similar type of or different types.

Component b

4-position component with flow rate regulation, double acting and automatic return to neutral.

Component c

4-position component with flow rate regulation, double acting, zero leak and automatic return to neutral.

Couplers

The quick-disconnect couplings are held by a bracket on the centre housing. They are sealed by covers of different colours (red, green, black or yellow) corresponding respectively to hydraulic ports A and B of auxiliary spool valves.

When the auxiliary spool valve is at rest, a lever system (1) allows existing pressure to be relieved into the hydraulic hoses (2). These hoses link the spool valves with the concerned couplers (3).

By acting on this system, the clean oil under pressure is directed to the return via a hose and pipe assembly (4) connected to the upper part of the intermediate housing. This drop in pressure facilitates the connecting of the male coupler to the female coupler.

The contaminated oil, coming from the separation of the couplers, flows into flexible and transparent tanks (5) located on either side of the third-point linkage.

Operation

When the lever in the cab is pulled (spool (1) pushed), the oil enters via channel P and travels towards the restrictor of the flow regulation control spool (5) and grooves of the main spool (1).

The oil is then carried towards a main channel and lifts the ball of valve (2) to enter a chamber. Displacement of the spool (1) simultaneously opens the one-way valve (3).

The oil flows from the chamber towards port A and returns to the housing through port B via the hydraulic slave device.

The operating principle is identical when the lever is pushed (spool (1) pulled). The oil flows from the chamber towards port B and returns to the housing through port A via the hydraulic slave device.

Layout of components and identification of ports

(1) Main spool (2) Valve (3) Non-return valve (4) Flow regulation control rod (5) Flow regulation control spool (6) Housing and locking system (7) Flow regulation control button

Removing and install the spool valve blocks

Disconnect the control cables (7) of each spool valve component by uncoupling the sleeves (1) located under the cab.

Mark the position of the hydraulics hoses connected to the couplers. Disconnect them from the MF 7499, 7495 spool valve block.

Disconnect:

- the high pressure pipe;
- the lift ram supply pipes;
- the LS hose.

Mark and disconnect the lift control valve solenoid valve harness (R10 Down - R11 Up).

Removal

Remove the screws and flanges from the manifold. Sling the MF 7495, 7499 spool valve block.

Separate it from the support. Place it in a clean work area.

If necessary, remove support. Discard the O'ring.

Reinstall

If it was necessary to remove the support, replace the return pipe O’rings. Tighten the screws.

Clean the manifold mating face, along with that of the support.

If the studs need replacing, lightly smear the short thread of the new studs with Loctite 270 or equivalent. Install and tighten the studs. Clean off any excess Loctite.

Replace the O’ring. Reinstall the spool valve block on the support.

Tighten:

- the screws to a torque of 50 - 70 Nm;
- the nuts to a torque of 90 - 120 Nm.

Assembling and adjusting a control cable

To be performed on the console

Remove right-hand console cover.
Install the unit (1) and its control cable on the suitable fixture.
Install the console cover.

To be performed on the Massey Ferguson 7499, 7495 auxiliary spool valve

Check, without turning, that the valve spool is in neutral position.
Screw clevis (1) flush with the threaded part of cable (7). Tighten nut (3). Fit the pin (4).

Screw:

- the bell housing (8), partially;
- the screws (6) without tightening them.

Adjust the bell housing (8) by turning it from left to right to centre the lever (1) in the console opening.