Genuine Honda coolant drain plug washer 28 mm – 90401-PR4-000

Genuine Honda coolant drain plug washer – 90401-PR4-000 (28 mm)

Genuine Honda sealing washer with part number 90401-PR4-000 (90401PR4000), used under the coolant drain plug in the engine block. It provides a tight seal between the drain bolt and the block, preventing coolant leaks and loss of pressure in the cooling system.

The washer has an outer diameter of 28 mm and is a single-use service item – it should be replaced every time the engine block coolant drain plug is removed. Using the genuine Honda washer greatly reduces the risk of micro leaks that often occur when using generic or incorrect-size sealing washers.

Applications

Washer 90401-PR4-000 is used across a very wide range of Honda and Acura models and engines. Because of the large number of possible applications and market variations, it is strongly recommended to confirm the part number by VIN in the official Honda parts catalogue before ordering.

• Acura NSX 2017–2021
• Acura MDX 2014–2024
• Acura RDX 2015–2024
• Acura TLX 2015–2024
• Honda Accord 2D 2008–2017 (USA)
• Honda Accord E:HEV 2023–2025 (USA)
• Honda Accord 4D 1999–2015
• Honda Accord 5D 1999–2002
• Honda Accord Coupe 1998–2002
• Honda Accord Tourer 2003–2015
• Honda City 2009–2010
• Honda Civic 3D 1992–2011
• Honda Civic 4D 1992–2021
• Honda Civic 4D Diesel 2018–2020
• Honda Civic 5D 1995–2021
• Honda Civic 5D Diesel 2018–2020
• Honda Civic 5D E:HEV 2023–2026
• Honda Civic 5D Type-R 2015–2025
• Honda Civic Aerodeck 1998–1999
• Honda Civic Coupe 1994–2005
• Honda Civic CRX 1992–1997
• Honda Civic Hybrid 2003–2011
• Honda Civic Shuttle 1991–1995
• Honda Civic Tourer 2014–2017
• Honda Concerto 1991–1993
• Honda CR-V 1997–2023
• Honda CR-V Diesel 2015–2018
• Honda CR-V E:HEV 2021–2025
• Honda CR-V E:PHEV 2024–2026
• Honda CR-V Hybrid 2019–2020
• Honda CR-V I-CTDI 2005–2009
• Honda CR-V I-DTEC 2010–2017
• Honda CR-Z 2011–2013
• Honda FR-V 2005–2009
• Honda HR-V 1999–2005
• Honda HR-V 2015–2019
• Honda HR-V Diesel 2019–2020
• Honda HR-V E:HEV 2022–2026
• Honda Pilot 2011–2022
• Honda Pilot 2009; 2023–2024
• Honda S2000 2000–2009
• Honda Insight 2000–2013
• Honda Integra 3D 1998–2000
• Honda Jazz 2002–2020
• Honda Jazz E:HEV 2021–2026
• Honda Jazz Hybrid 2012–2015
• Honda Legend 4D 2007–2010
• Honda Logo 3D 1999–2000
• Honda NSX 2017–2021
• Honda Odyssey 1998–2026
• Honda Prelude 1998–2001; 2026–
• Honda Shuttle 1998–1999
• Honda Stream 2001–2005
• Honda ZR-V E:HEV 2023–2026

OEM number

The part offered here is exactly the following genuine Honda catalogue number:

• 90401-PR4-000 – genuine coolant drain plug washer for the engine block (28 mm outer diameter)
• 90401PR4000 – alternative writing of the same part number used in some catalogues

When to replace – leak symptoms

• visible coolant traces around the engine block drain plug,
• wet areas, white/coloured deposits or “crystals” from dried coolant near the drain bolt,
• slow coolant loss requiring regular topping up without obvious large leaks,
• clearly deformed, cracked or crushed washer after removing the drain plug,
• the same washer has been reused over several coolant changes.

A worn or reused washer may no longer seal correctly. Replacing this small part at every coolant change is an inexpensive way to prevent later leaks and the need to re-bleed the cooling system.

Installation and service tips

• always install the washer on a clean, degreased surface under the head of the coolant drain plug in the block,
• clean the drain hole area and the seating face on the block from dirt and deposits before fitting the new washer,
• always use a new washer – reusing the old one is not recommended,
• tighten the drain plug carefully or to the torque specified in the workshop manual to avoid damaging the thread or the seating surface in the (often aluminium) block,
• after refilling the cooling system and bleeding it, run the engine up to operating temperature and check the area around the drain plug for leaks,
• replace the washer with a new one at every future coolant change or whenever the block drain plug is removed.

FAQ – frequently asked questions about Honda coolant drain plug washer 90401-PR4-000

Does this washer fit every model listed?
Washer 90401-PR4-000 has very wide coverage, but there can be differences between markets and model years. The most reliable method is always to check the part number by VIN in the official Honda parts system.

Can this washer be used for the engine oil drain plug?
No. Part number 90401-PR4-000 is designed specifically for the engine block coolant drain plug. For the oil drain plug, you should use the washer specified for that engine.

Can I reuse this washer several times?
This is not recommended. The washer deforms slightly when the plug is tightened and should be replaced whenever the block drain plug is removed or the coolant is changed.

Why choose the genuine Honda washer instead of a universal one?
The genuine washer has the correct 28 mm diameter, thickness and material hardness for the specific seat in the engine block. This ensures reliable sealing without over-tightening the plug, which helps protect the thread and sealing face in the block.