Page 1 of 3

Technical Service Bulletin
SUBJECT:

INSPECTION CRITERIA FOR LEAKING SHOCK
ABSORBERS

No:

TSB−18−33−001

DATE:

April 2018

MODEL:

All Models

CIRCULATE TO:

[ ] GENERAL MANAGER

[ X ] PARTS MANAGER

[ X ] TECHNICIAN

[ X ] SERVICE ADVISOR

[ X ] SERVICE MANAGER

[ X ] WARRANTY PROCESSOR

[ ] SALES MANAGER

This bulletin supercedes TSB−10−33−001, issued January, 2010, to add more details of oil leakage
severity. Revisions are italicized and indicated by A.

PURPOSE
This TSB provides instructions for shock absorber inspection, and criteria for determining oil leak
severity to help dealers judge whether a shock absorber requires replacement.

AFFECTED VEHICLES
All models

DESCRIPTION
When inspecting shock absorbers, oil seen on the surface is not always an indication of a seal failure
requiring shock replacement.
Shock absorber seals perform 3 functions:
1. seal the shock absorber oil inside the cylinder.
2. prevent dust from entering the cylinder.
3. spread an even film of oil to lubricate the piston rod and seal.
Oil Film = necessary for lubrication, durability of seal
Compression Stroke

Rebound Stroke

Oil Film Scraped

Formation of Oil Film

Off by Dust Seal

Dust Lip
Piston Rod

Oil
Film

Main Lip

Oil

"
"

Shock absorbers lose a small amount of oil during use and this is considered normal. As the piston rod
travels through compression and rebound strokes during shock absorber operation, a film of oil adheres
to its surface, bypassing the seal. This helps lubricate and extend the life of the seal. During compression
of the shock absorber, oil is scraped off the piston rod by the seal's dust lip and accumulates on the outer
surface of the shock absorber. This small amount of oil does not always indicate a defective shock
absorber.
Copyright 2018, Mitsubishi Motors North America, Inc.

Continued

The information contained in this bulletin is subject to change. For the latest version of this document, go to the Mitsubishi Dealer Link,
MEDIC, or the Mitsubishi Service Information website (www.mitsubishitechinfo.com).
(4603)

Page 2 of 3
TSB−18−33−001

PROCEDURE
SHOCK ABSORBER VISUAL INSPECTION FLOWCHART
Use the Shock Absorber Visual Inspection Flowchart when inspecting shock absorbers. If there is oil
visible on the shock's surface, use the Oil Leak Severity Guidelines to determine the extent of the leak,
and proceed according to comments in the Remarks column.

SHOCK ABSORBER VISUAL INSPECTION FLOWCHART
Start
Inspection of shock absorber
No

Visible trace of oil

END

Yes
Determine the level of leak severity of shock absorber.
(Refer to Oil Leak Severity Guidelines)

What is the level of severity?
Level 2 or 3

Clean oil and dust, sand,
undercoating
adhered to shock absorber.
(Normal oil
END
adhesion, No defect)

(Oil leak due to defect)

Replace the shock absorber.
END

Level 1

Page 3 of 3
TSB−18−33−001

OIL LEAK SEVERITY GUIDELINES
Level

Shock Absorber with
Spring Seat (strut)

Shock Absorber without
Spring Seat

Visible oil pattern is
less than ⅓ the
length of the shock
absorber body
length (L).

1
"
Trace of Oil

Trace of Oil
Less than 1/3L

Less than 1/3L

Seam weld

Sealed case

"

Spring sheet

Remarks

Knuckle
bracket
Case-end
caulking

Appearance of oil in
this pattern does
not suggest a
progressive oil leak.
Replacement is
NOT recommended
and is NOT a
warranty covered
condition.

Band-like oil
dripping (length is
irrelevant).

2

Appearance of oil in
this pattern
suggests a leak in a
short time span.

"

Replacement is
recommended.

3

Trace of Oil

"
More than 1/3L

Trace of Oil

Visible oil pattern is
more than ⅓ the
length of the shock
absorber body
length (L).

More than 1/3L

Visible oil pattern at
this level indicates
the leak is
progressing.
Replacement is
recommended.

WARRANTY INFORMATION
This TSB provides information only. When replacing shock absorbers, refer to the LOTS for repair
operation numbers and labor times.
DO NOT replace shock absorbers categorized in level 1.
"

Shock absorbers categorized in level 2 or 3 should be replaced. DO NOT replace shock absorbers as
an axle set (right and left on same axle) unless BOTH show level 2 or 3 leakage. Replace leaking
shock absorbers only.