2523591C91 | Genuine OEM International/Navistar Diesel Exhaust Fluid DEF Header 25"

The 2523591C91 Genuine OEM International/Navistar Diesel Exhaust Fluid (DEF) Header is a tank-mounted component designed for compatible diesel emissions systems. This 25-inch DEF header assembly supports monitoring of DEF tank conditions to help the vehicle's selective catalytic reduction (SCR) system operate according to its design.

PRODUCT INFORMATION

• Part Number: 2523591C91
• Brand: International / Navistar
• Condition: Genuine OEM — confirm the item's actual condition with the seller
• Component: Diesel Exhaust Fluid (DEF) Header
• Header Length: 25 inches
• System: DEF / SCR Emissions System
• Tank Applications: 10.6-gallon to 32-gallon DEF tanks, subject to fitment verification

APPLICATIONS

This DEF Header is listed for compatible tank configurations ranging from 10.6 to 32 gallons. Exact compatibility depends on the vehicle model, model year, tank capacity and shape, header length, electrical connector, and original part number. Verify the application before ordering, as different DEF header assemblies may not be interchangeable.

FUNCTION

The DEF Header is installed in the DEF tank assembly and supports monitoring of fluid conditions through the sensors fitted to the specific configuration. Depending on the design, these may measure DEF level, quality, and temperature. The resulting signals help the vehicle's emissions control system manage diesel exhaust fluid operation.

SIGNS OF A FAULTY DEF HEADER

A faulty DEF Header or related system issue may cause:

• Incorrect or inconsistent DEF level readings
• DEF quality or temperature sensor fault codes
• Check engine or emissions system warning lights
• SCR system warnings or fault messages
• DEF system performance or communication issues
• Emissions-related derate warnings on applicable vehicles

These symptoms may also result from wiring faults, contaminated DEF, connector problems, or other emissions system components. Proper diagnostics are recommended before replacing the header.

WHY REPLACE THE DEF HEADER?

Replacing a confirmed faulty DEF Header with the correct compatible unit can help restore accurate tank monitoring and normal DEF system operation. Depending on the vehicle, fault-code clearing, system checks, or additional diagnostic procedures may be required after installation.

FITMENT INFORMATION

Verify that part number 2523591C91 matches the original DEF header before ordering. Compatibility depends on the vehicle model year, tank capacity and configuration, header length, connector type, and emissions system. Tank capacity alone is not sufficient to confirm fitment.

If you are unsure whether this part is correct for your vehicle, please contact us with your VIN and original DEF header part number. We are happy to help verify compatibility before purchase.

GENUINE INTERNATIONAL / NAVISTAR PART

Part Number: 2523591C91