L-SB-0039-20

October 16, 2020

Water Pump Leak Inspection and Diagnostic Tips
Service
Category

Engine/Hybrid System

Section

Cooling

Market USA

Applicability
YEAR(S)

MODEL(S)

2019 - 2021

ES350, GS350

2016 - 2020

GS F

2016 - 2019

GS200T, GS300

2010 - 2021

GX460

2016 - 2021

IS200T, IS300, RC200T,
RC300, RX350, RX450H

2018 - 2021

IS350, LC500, LC500C,
LC500H, LS500, LS500H,
RC350

ADDITIONAL INFORMATION

2008 - 2011, 2013 - 2021 LX570
2015 - 2021

NX200T, NX300, NX300H,
RC F

Introduction

This Service Bulletin provides updated non-electric water pump leak inspection and diagnostic tips
for some 2008 – 2021 model year Lexus vehicles.

© 2020 Lexus, a division of Toyota Motor Sales, USA

Page 1 of 8

L-SB-0039-20

October 16, 2020

Page 2 of 8

Water Pump Leak Inspection and Diagnostic Tips
Warranty Information
OP CODE

DESCRIPTION

TIME

OFP

T1

T2

N/A

Not Applicable to Warranty

–

–

–

–

APPLICABLE WARRANTY
 Warranty coverage is based on the failed component. Please refer to the Warranty Policy and
Procedures Manual and the Powertrain Parts List for specific coverage.
 Warranty application is limited to occurrence of the specified condition described in
this bulletin.
Warranty and Claim Submission: Warranty Policy 4.18.



ANY leak repair to be performed under warranty requires photo documentation of the
active leak.



This documentation showing the cause of the defect MUST be created prior to the start of the
repair and attached to the warranty claim.



Photos MUST be clear and provide perspective image(s) that identify the vehicle identification
number (VIN) and the affected component(s), and close-up image(s) that illustrate the defect
or condition.



For additional information regarding application and eligibility, please reference
Warranty Policy 4.18.



Water Pump Construction ......................................................................................................... 3

Procedures



Evaporation Port and Drain Plug ........................................................................................ 3



Mechanical Seal ................................................................................................................. 4



Temporary and Active Leaks .................................................................................................... 5



Water Pump Replacement ........................................................................................................ 7


Diagnostic Procedure ......................................................................................................... 7

© 2020 Lexus, a division of Toyota Motor Sales, USA

L-SB-0039-20

October 16, 2020

Water Pump Leak Inspection and Diagnostic Tips
Water Pump Construction
Evaporation Port and Drain Plug
Figure 1. Typical Pump Assembly

1

2

3
4

1

Evaporation Port

3

Drain Pocket

2

Mechanical Seal

4

Drain Plug

© 2020 Lexus, a division of Toyota Motor Sales, USA

Page 3 of 8

L-SB-0039-20

October 16, 2020

Page 4 of 8

Water Pump Leak Inspection and Diagnostic Tips
Water Pump Construction (continued)
Mechanical Seal

The water pump shaft is sealed by a mechanical type seal.
Figure 2. Mechanical Seal

1
2
3

4
5

1

Spring – Applies Pressure to The Seal Ring To
Ensure The Seal Ring And Mating Ring are in
Constant Contact

4

Cartridge – Locates the Seal Ring and Bellows
in the Water Pump Housing

2

Seal Ring – Stationary Sealing Member in the
Water Pump Housing, Held in Place by
the Cartridge

5

Bellows – Seals the Cartridge and the Seal Ring

3

Mating Ring – Rotates With the Water Pump Shaft
and Provides a Sealing Surface for the
Seal Ring

© 2020 Lexus, a division of Toyota Motor Sales, USA

L-SB-0039-20

October 16, 2020

Page 5 of 8

Water Pump Leak Inspection and Diagnostic Tips
Temporary and Active Leaks

Water pump replacement is NOT necessary for a temporary leak condition. The water pump
should be replaced for an active leak condition. Examples of both conditions are shown below:


As the water pump assembly rotates, a small amount of engine coolant is discharged to cool
and lubricate the sliding surface of the mechanical seal and evaporates.
Figure 3. Temporary Leak – Dry Coolant Residue
(Do Not Replace the Water Pump)

Figure 4. Active Leak Leak – Wet Coolant
Residue/Drips (Replace the Water Pump)

© 2020 Lexus, a division of Toyota Motor Sales, USA

L-SB-0039-20

October 16, 2020

Page 6 of 8

Water Pump Leak Inspection and Diagnostic Tips
Temporary and Active Leaks (continued)



If debris becomes lodged between the
mating ring and seal ring, a small gap is
formed. This allows coolant to bypass the
mechanical seal, flow into the fluid catch
pocket, and drain out of the weep hole. This
condition is temporary and will no longer be
present once the debris breaks up or works
its way out of the seal.

Figure 5. Debris in Mechanical Seal
3

A

2

1

4
B

5
C

1

Mating Ring

2

Seal Ring

3

Spring

4

Cartridge

5

Bellows

A

Housing Side

B

Impeller Side

C

Gap Formed by Debris

© 2020 Lexus, a division of Toyota Motor Sales, USA

L-SB-0039-20

October 16, 2020

Page 7 of 8

Water Pump Leak Inspection and Diagnostic Tips
Water Pump Replacement
Diagnostic Procedure

1. Confirm if there are leaks present from areas in the cooling system not including from the
water pump assembly.
NOTE
Refer to the applicable model and model year Repair Manual at TIS – Cooling System – OnVehicle Inspection – Inspect for Coolant Leak.

Are ANY leaks present in the cooling system other than from the water pump?


YES — Continue leak diagnosis using the applicable model and model year
Repair Manual and correct any other cooling system leaks BEFORE proceeding.



NO — Continue to step 2.

2. Is the coolant level below the “low” indicator in the reservoir and does the water pump
appear to be actively leaking?


YES — Replace the water pump. Refer to the applicable model and model year
Repair Manual.



NO — Continue to step 3.

3. Does the water pump pulley/bearing have excessive free play or does NOT turn smoothly?


YES — Replace the water pump. Refer to the applicable model and model year
Repair Manual.



NO — Continue to step 4.

© 2020 Lexus, a division of Toyota Motor Sales, USA

L-SB-0039-20

October 16, 2020

Page 8 of 8

Water Pump Leak Inspection and Diagnostic Tips
Water Pump Replacement (continued)
Diagnostic Procedure (continued)

4. A paper towel should be used to determine if a leak is current or was temporary due to
debris that has now cleared. Apply a dry paper towel to the coolant deposits around the
water pump. If the paper towel remains dry, the leak was temporary and the water pump
does NOT need to be replaced. If the paper towel becomes wet with coolant, the leak is
active and the water pump should be replaced.
Figure 6.

1

A
2

A

Apply a Dry Paper Towel to the Coolant Deposits

2

Wet Paper Towel

1

Dry Paper Towel

Is the paper towel wet with coolant?


YES — Replace the water pump. Refer to the applicable model and model year
Repair Manual.



NO — No active leak is present. Confirm the coolant level in the reservoir is correct,
adjust as necessary, and return the vehicle to the customer.
NOTE
Thoroughly clean ANY coolant residue from the engine and surrounding areas.

© 2020 Lexus, a division of Toyota Motor Sales, USA