Thomas 153 Repair Manual

1
C4250
C1865
C4476
1-37
Before performing this test, ensure the control linkages
are not binding and the hydraulic control valve spools are
centering in the neutral position. Check the hydraulic
circuit for external leaks. These conditions will give the
same symptoms as a worn piston seal. If the cylinders
under pressure are sluggish or stop functioning, these
would indicate that oil is leaking by the cylinder piston
seal. The following test can be performed to check the
cylinder piston seal.
1 Retract the cylinder(s) to be tested. Shut off the
engine and cycle the controls to release the hydraulic
pressure. Have a container can ready to catch any waste
oil to prevent environmental contamination.
2 Disconnect the hoses from the cylinder to be tested.
Cap the hose with a plug to prevent contamination.
3. Disconnect the cylinder to be tested as outline on
page 1-38 or 1-39.
4. Place the base or fixed end of the cylinder in a vice
or support to hold the cylinder.
5. Extend the cylinder ram about 6 ~ 8”. Fill the fixed
end cylinder port with hydraulic oil using a funnel.
6. Cap both ports with a 3/4 JIC steel cap to prevent
system pressure from escaping.
7. Apply pressure using your hand to the ram.
6 Monitor the movement of the ram. If the ram slowly
retract back to it original position, then the seals are bad
and need replacement. If the cylinder stays extended then
you may need to check the load check valves or spool
wear in the hydraulic control valve.
7 Repeat for all both pairs of cylinders.
8. If the cylinder passed the piston seal test then
assemble the cylinder to the loader.
Testing the Piston Seals
HYDRAULIC CYLINDERS 1.4
WARNING
Use extreme caution when checking the hydraulic
system for leaks. Fluid under pressure can penetrate
the skin and cause serious injury.
Remove cylinder to be tested
Remove cylinder to be tested
C4477
Allowable boom or bucket cylinder drop: 1.5” in 3
minutes, @ loaded rating and operating
temperature.
IMPORTANT
Extend cylinder 6 ~8”
Slowly retract the ram

Thomas 153 Specifications

General

Brand	Thomas
Model	153
Category	Compact Loader
Language	English