TEST OR INSPECTION
HYDRAULIC SYSTEM - CONT
Check platform drift in front suspension while gooseneck isolation valve is in RUN mode by
uncoupling tractor and semitrailer while in ADJUST mode with front support legs 3 inches (7.6 cm) off
the ground. Pilot check valves in suspension control manifold may be contaminated or leaking.
a. Clear contamination by raising platform (para. 2-19) to near full height and lowering platform to
near fully lowered for three or more full cycles of operation. While raising and lowering platform,
abruptly release and reverse handles several times each cycle.
b. If platform drifts downward at a steady or even rate, counter balance valves CB1 (curbside) and
CB2 (streetside) may be leaking internally or around valves. Remove and clean valves. Reinstall
Clean and repair or replace parts as
SUSPENSION RIDES STIFF AND DOES NOT ADJUST FOR BUMPS/ROAD HAZARDS
Check that axle suspension isolation valves are open.
Check that suspension isolation valve handle operates both valves equally and is secure. Tighten or
For highway driving or when semitrailer and tractor are coupled, gooseneck isolation valve should be
Be sure all four support legs (para. 2-22 and 2-23) are lowered and supporting the
platform prior to checking the gooseneck isolation valve handles for proper
operation or injury to personnel may result.
a. Linkage should be tight and adjusted so that all valve handles move the same distance and open
each valve equally. Adjust valve linkage as required (para. 4-84).
b. Check each valve handle to be sure both valves are being operated. Tighten or remove and