BUSHING 6E4381 - Caterpillar

Makeup Valve Operation
Illustration 1 g00854676
(1) Spring (2) Valve cartridge (3) Passage from the low pressure side of the drive loop (4) Passage (5) Supply passage of charge oil from the hydraulic oil filterWhen the pressure in passage (3) and the force of spring (1) is less than the charge oil pressure in passage (4) , charge oil pressure forces valve cartridge (2) upward. Charge oil flows from passage (5) through passage (4) to valve cartridge (2) . The oil flows past valve cartridge (2) through passage (3) back to the drive loop.Relief Valve Operation
Illustration 2 g00854677
(1) Charge relief valve (2) Passage from the high pressure side of the drive loop (3) Poppet (4) Spring (5) Spring retainerOil flows from the drive loop to the crossover relief valve through passage (2) . Pressure oil acts against the surface of poppet (3) . Since poppet (3) screws into spring retainer (5) , the spring retainer attempts to compress spring (4) . When the pressure of the oil overcomes the force of spring (4) , the poppet moves upward. Oil flows from passage (2) past poppet (3) to charge relief valve (1) . The oil flows through charge relief valve (1) to the case drain. Refer to Systems Operation, "Relief Valve (Charge)" for additional information on the operation of the charge relief valve.