BLOCK 5I4083 - Caterpillar

There are two make-up valves in the hydraulic system. Make-up valve (5) is in the rod end of the lift circuit and make-up valve (6) is in the rod end of the tilt circuit. Housing (7) is fastened directly to the lift and tilt control valve. The make-up valves will permit oil from the return line to add with pump oil when the cylinder rods are retracted faster than the pump can supply oil to the cylinders. Orifice (8) causes a restriction to the flow of oil back to the oil tank. The orifice makes sure that there is enough oil available at the make-up valves so that there is no cavitation (vacuum) in the cylinders.Make-up valve (6) operates when the rod end of the tilt cylinder is retracted fast when the bucket is dumped. When the pressure in passage (2) decreases enough, the pressure in passage (9) will become greater than the force of spring (4). Make-up valve (6) will move up and oil from passage (9) will go into passage (2) and add to the oil in the rod end of the tilt cylinder. Make-up valve (6) will operate in the same way when an outside force on the bucket causes the tilt cylinder to be retracted.Make-up valve (5) operates the same way as make-up valve (6). Make-up valve (5) operates when the lift arms are lowered.
MAKE-UP VALVES
1. Passage from rod end of lift cylinders. 2. Passage from rod end of tilt cylinder. 3. Spring. 4. Spring. 5. Make-up valve. 6. Make-up valve. 7. Housing. 8. Orifice. 9. Inlet passage for return oil. 10. Outlet passage for return oil.