307C Excavator Hydraulic System Caterpillar

Illustration 1	g00755237
Rear view of hydraulic tank (10) Pilot relief valve (11) Pilot filter (12) Port (13) Line

Illustration 2	g00754839
Pilot Filter (10) Pilot relief valve (11) Pilot filter (12) Port (14) Filter element (15) Bypass relief valve

Pilot relief valve (10) is attached to pilot filter (11). The pilot relief valve limits the oil pressure in the pilot circuit to 4100 kPa (595 psi). When the oil pressure in line (13) increases to the pilot relief valve pressure, valve (10) opens in order to allow part of the oil in port (12) to return to the hydraulic tank.