2018-2020 Honda Accord Cylinder Head Gasket Warranty Extension

Honda has released Service Bulletin 26-004, Version 3, dated September 25, 2026, to address potential issues with the cylinder head gasket in certain 2018-2020 Honda Accord vehicles equipped with a manual transmission. This bulletin supersedes version 2 and provides an important warranty extension for owners experiencing specific engine problems. The primary concern is reduced effectiveness of the cylinder head gasket, which can lead to significant engine malfunctions.

Owners of affected 2018-2020 Honda Accord manual transmission vehicles may notice several symptoms indicating a problem with the Honda Accord cylinder head gasket. These include engine overheating, unexplained coolant loss, and engine misfire. These issues can arise under various driving conditions due to the compromised integrity of the head gasket.

In some cases, the cylinder head gasket issue may trigger specific diagnostic trouble codes (DTCs). These include P0300 (Random/Multiple Cylinder Misfire Detected) and P0301, P0302, P0303, P0304 (Cylinder 1, 2, 3, or 4 Misfire Detected). It is important to note that while these DTCs may be present, they are not a mandatory requirement for a repair under this warranty extension. An ALL DTC check result with or without these specific codes is acceptable for warranty claims.

To enhance customer satisfaction and confidence, American Honda is significantly extending the warranty coverage for the Honda Accord cylinder head gasket condition. The new coverage is 10 years from the original date of purchase or 150,000 miles, whichever occurs first. This extended warranty is notable as it applies to any vehicle, even if it has been declared a total loss or sold for salvage by a financial institution or insurer, or has a branded or similar title under any state's law. This ensures a broad range of owners are protected.

Important Warnings

Owners and technicians should be aware of several critical advisories outlined in Service Bulletin 26-004.

• "Do not call for approval if the cylinder head and engine block are within specifications." This prevents unnecessary contact with the Repair Verification Team if no warpage is found during inspection.
• During the short block replacement procedure, specifically when removing the clutch slave cylinder, technicians are advised: "Do not press the clutch pedal after the slave cylinder has been moved." and "Do not disconnect the clutch line joints." Adhering to these instructions is crucial to avoid further complications.
• Warranty claims that include cylinder head or short block replacement will be denied if prior approval from the Repair Verification Team is not received, as outlined in the Job Aid.
• Claims submitted without the ALL DTC check printout and borescope image will be denied.

Diagnosis

Diagnosing the Honda Accord cylinder head gasket issue in the 2018-2020 Honda Accord begins with a cold engine. Technicians must perform an ALL DTC Check using i-HDS and document any stored PGM-FI DTCs. A crucial step involves checking the cooling system pressure. If the pressure is below 18 psi, it should be brought up to 18 psi using a pressure tester. The primary diagnostic method involves using a borescope to inspect all cylinders for coolant leakage from the head gasket. This inspection requires removing the spark plugs and inserting a borescope with a 90-degree camera to scan the area where the cylinder head meets the block. If coolant is observed, a picture must be taken showing the borescope, a sticky note with VIN, repair order number, date, and the engine number, and the image of the leak. This image must be submitted with the warranty claim.

Repair Procedure Summary

Service Bulletin 26-004 outlines detailed repair procedures depending on the extent of the cylinder head gasket damage and any resulting component warpage. The core corrective action involves replacing the cylinder head gasket if coolant is leaking into the combustion chamber. If inspection reveals warpage of the cylinder head or engine block, these components will also be replaced as necessary.

The bulletin describes four distinct repair scenarios:

1. Head Gasket Only Replacement (Operation Number 1105E2): This procedure is for cases where only the head gasket needs replacement. It involves inspecting for coolant leaks, removing the cylinder head, checking for warpage, replacing the head gasket, and clearing DTCs. The flat rate time for this operation is 11.5 hours.
2. Head Gasket and Cylinder Head Replacement (Operation Number 1105E3): If the cylinder head is warped in addition to a leaking gasket, this procedure is followed. It includes all steps from the head gasket replacement, plus replacing the cylinder head itself. This operation has a flat rate time of 12.0 hours.
3. Head Gasket and Short Block Replacement (Operation Number 1105E4): When the engine block is warped or cracked, the short block is replaced along with the head gasket. This is a more extensive repair with a flat rate time of 14.7 hours.
4. Head Gasket, Cylinder Head, and Short Block Replacement (Operation Number 1105E5): This is the most comprehensive repair, performed if both the cylinder head and engine block are found to be warped or cracked. It combines the replacement of the head gasket, cylinder head, and engine short block, with a flat rate time of 14.8 hours.

All procedures involve significant engine disassembly, including removing components such as the alternator, water passage housing, A/C compressor, various sensors like the knock sensor and CKP sensor, and both left and right driveshafts. For manual transmission models, the clutch slave cylinder, transmission mounting bolts, and potentially the entire engine and transmission assembly are removed. Specific torque values are provided for reassembly of bolts and nuts, such as 30 N-m (22 lb-ft) for cylinder head bolts and 118 N-m (87 lb-ft) for flywheel mounting bolts. New gaskets, oil seals, and O-rings are required throughout the reassembly process. Final steps include refilling engine oil and transmission fluid, performing idle speed and ignition timing inspections, and resetting the Maintenance Minder system for engine oil, coolant, and transmission fluid. An alignment is also required if the short block was replaced.

Required Tools and Parts

Performing the repairs outlined in Service Bulletin 26-004 requires a comprehensive set of specialized and general tools, as well as numerous replacement parts to ensure a complete and lasting repair. Key diagnostic and repair tools specified include:

• Cooling System Pressure Tester (Part Number SVTS272A)
• Snap-on 5.5 mm Borescope (Part Number BK5600Dual55 or equivalent), essential for inspecting cylinders for coolant leaks.
• Engine Support Hanger Tool (Part Number AART1256)
• Universal Lift Eyelet (Part Number 07AAK-SNAA600) and Support Eyelets (Part Number 07AAK-SNAA120), used with spacers (Part Number 07AAB-59BA110) for engine removal and installation.
• Torque Angle Gauge (TA360 or Commercially Available) for precise bolt tightening.
• Straight Edge 18" (Part Number 07AAJ-59BA110) and Feeler Gauge (Part Number 07AAJ-59BA120) for checking component warpage.
• Clutch Alignment Tool (Part Number 07ZAF-PR8A100), Remover Handle (Part Number 07936-3710100), Ring Gear Holder (Part Number 07LAB-PV00100), and Ring Gear Holder Set (Part Number 070AB-5S1A100) are critical for manual transmission work.

Required materials and replacement parts are extensive and vary depending on the repair procedure. Common items include:

• Hondabond HT (Part Number 08718-0004)
• Various Brake Cleaners (e.g., 08700-9200, 08700-9222, 08700-SBPCA)
• Long Life Antifreeze/Coolant Type 2 (Part Number 08CLA-P99-0F0A8)
• Honda Manual Transmission Fluid (Part Number 08798-9031)
• Honda 0W-20 Motor Oil (Part Number 08798-9163)
• Red Scotch-Brite® or equivalent for surface preparation.
• Crucially, the GASKET, CYLINDER HEAD (NIPPON LEAKLESS) (Part Number 12251-6A0-A11) is replaced.
• Other gaskets include the HEAD COVER (12341-59B-013), OIL FILTER (15400-RTA-003), and various turbocharger and exhaust gaskets.
• If replacing major components, a new GENERAL ASSY., CYLINDER HEAD (Part Number 10003-6A0-A00) or GENERAL ASSY., CYLINDER BLOCK (Part Number 10002-6A0-A02) will be required.
• Numerous bolts, nuts, and O-rings are also listed, such as BOLT, FLANGE (12X40) (90162-T0A-A00), NUT, SELF-LOCK (10MM) (90012-59B-004), and OIL SEAL (43X58X7) (91212-59B-003). Specific part numbers are provided for each component to ensure correct replacement.

Owner Action

If you own a 2018-2020 Honda Accord manual transmission and are experiencing symptoms such as engine overheating, coolant loss, or misfires, you should contact an authorized Honda automobile dealer. Owners of affected vehicles will be sent a notification regarding this campaign. It is recommended to have your VIN status checked by the dealer to confirm eligibility for this warranty extension. The dealer will perform the necessary diagnostic procedures, including the ALL DTC check and borescope inspection, to determine the appropriate repair under Service Bulletin 26-004. This extended warranty covers the repair at no cost to the owner for 10 years or 150,000 miles, whichever comes first.

NHTSA ID: 11037688