A hydraulic flush after a component failure is contamination control, not an oil change. When a pump, motor or cylinder fails it releases metal and seal material into a circuit holding hundreds of liters that reaches every actuator. The flush runs in stages: remove the failed component and clean the tank, replace every filter and clean the suction strainers, refill with the specified oil, then stroke every function at low pressure so flow carries debris to the filters instead of past them. Filters are changed at short intervals, the first after a few hours and the second after tens, and the job is finished when a laboratory particle count meets the target ISO code. Finishing on how the oil looks is how a rebuilt pump fails inside a month.
Stage and acceptance
| Stage | Done when |
|---|---|
| First sample | An ISO code is on paper and the target is agreed before work starts |
| Component replaced and tank cleaned | Tank floor, baffles and magnet wipe clean on a white cloth |
| First fill and full filter set | All elements new, strainers clean, no leaks at first pressure |
| Low-pressure circulation | Every cylinder stroked, every motor turned, oil at working temperature |
| Second and third filter change | Laboratory count at or below the target code, not a visual check |
How to confirm it
- Take a particle count before touching anything
A sample from the tank at operating temperature gives the ISO 4406 code the flush has to beat and shows whether the failure debris has already circulated. It also documents the starting condition, which matters when the same machine fails again.
- Remove the failed component and read what it left behind
Cut the filter open and look at the debris. Brass and bronze say pump or motor, rubber says a seal, steel chips say a gear or a bearing. The material points at which circuits downstream are most at risk and which ones need opening.
- Drain the tank and clean it by hand
Through the access cover, wipe the tank floor and the baffles and clean the magnet. Debris settles in corners a drain plug never reaches, and a genuinely clean tank is the difference between one flush and three.
- Change every filter and clean the suction strainers
All of them, including pilot and return elements, at the first fill. A strainer left half blocked starves the new pump and the flush never gets the flow it needs to move debris out of the dead ends.
- Stroke every function at low pressure to move the oil
Warm the oil to working temperature, run each cylinder to full travel and turn each motor for a minute at a reduced relief setting. Closed centers and cylinder end chambers hold debris until something pushes oil through them.
- Change filters again and count until the target is met
First change after a few hours, second after tens of hours, with a sample at each. The flush is complete when the count reaches the target code, and not before, however clean the oil looks on the dipstick.
What to do about it
C
l
o
s
e
t
h
e
j
o
b
w
i
t
h
a
f
i
l
t
e
r
s
e
t
,
a
f
r
e
s
h
c
h
a
r
g
e
o
f
t
h
e
s
p
e
c
i
f
i
e
d
o
i
l
,
a
r
e
c
o
r
d
e
d
p
a
r
t
i
c
l
e
c
o
u
n
t
i
n
t
h
e
m
a
c
h
i
n
e
f
i
l
e
a
n
d
a
s
e
c
o
n
d
c
o
u
n
t
a
t
a
h
u
n
d
r
e
d
h
o
u
r
s
t
o
p
r
o
v
e
t
h
e
s
y
s
t
e
m
i
s
s
t
a
b
l
e
.
T
h
e
p
a
r
t
s
t
h
a
t
m
a
k
e
a
f
l
u
s
h
w
o
r
k
a
r
e
o
r
d
i
n
a
r
y
:
e
l
e
m
e
n
t
s
,
s
t
r
a
i
n
e
r
s
,
b
r
e
a
t
h
e
r
s
a
n
d
t
h
e
f
a
i
l
e
d
c
o
m
p
o
n
e
n
t
i
t
s
e
l
f
.
G
u
a
n
g
z
h
o
u
S
h
e
n
y
u
e
M
a
c
h
i
n
e
r
y
T
e
c
h
n
o
l
o
g
y
C
o
.
,
L
t
d
.
s
u
p
p
l
i
e
s
h
y
d
r
a
u
l
i
c
f
i
l
t
e
r
e
l
e
m
e
n
t
s
,
s
u
c
t
i
o
n
s
t
r
a
i
n
e
r
s
,
t
a
n
k
b
r
e
a
t
h
e
r
s
a
n
d
p
u
m
p
s
w
i
t
h
t
h
e
g
r
a
d
e
s
t
a
t
e
d
o
n
e
v
e
r
y
l
i
n
e
,
f
r
o
m
3
,
0
0
0
+
p
a
r
t
t
y
p
e
s
o
n
t
h
e
s
h
e
l
f
a
n
d
1
0
0
,
0
0
0
+
p
a
r
t
n
u
m
b
e
r
s
a
v
a
i
l
a
b
l
e
t
o
o
r
d
e
r
.
Parts you may need, by grade
| Part | Grades commonly quoted |
|---|---|
| Filter elements | Genuine or OEM-quality at the specified micron rating and beta ratio. A coarse element passes the debris the flush is trying to catch. |
| Suction strainers and breathers | Genuine or OEM-quality. A breather that does not seal puts dust into the cleanest oil in the system. |
| Replacement pumps and motors | Genuine, OEM-quality or clearly identified aftermarket matched to the model and displacement. The flush protects the warranty on all three. |
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
How much oil does a flush take?
Plan on the system capacity plus one change, and often two after a bad failure. The oil that comes out carries the debris and putting it back returns it. Filters are the larger cost, because a failure usually consumes three sets.
Can I flush with diesel or a flushing oil?
Follow the manufacturer. Some allow a dedicated flushing oil with a short run and a complete drain; others permit nothing but the specified hydraulic oil. Diesel is a solvent that leaves the system with no lubricity at the moment the new pump needs it most.
Why does the oil look clean while the count is still high?
Because silt-range debris is invisible. Particles under ten microns do the damage to clearances, and they are exactly what a particle count measures and the eye cannot see.