Navistar/International IC Bus International N9, N10, N13, DT DEF Head Unit

Precise DEF Leveling for International N9/N10/N13/DT: OEM DEF Head Unit (2523590C91), 2011‑2016

What is it?
The OEM 2523590C91 DEF Head Unit is the original equipment DEF (Diesel Exhaust Fluid) header assembly for Navistar / International N9, N10, N13, DT engines made between 2011 and 2016. As a QLS (Quiet Level Sensing) DEF tank head unit, it monitors fluid level and interfaces with the DEF system to maintain emissions compliance.

Why choose this OEM DEF Head Unit?
Built to Navistar’s specifications, this unit ensures correct sensor calibration, reliable seal integrity, and proper integration with your vehicle’s DEF and SCR systems. Non‑OEM parts often lead to fluid leaks, sensor errors, or warning codes—this genuine part avoids those issues.

Key Benefits
 ✅ Direct swap‑in for International / IC Bus N9, N10, N13, DT (2011‑2016)
 ✅ OEM sensors and header design for accurate DEF level sensing
 ✅ Proper sealing to prevent leaks or DEF contamination
 ✅ Helps avoid SCR/DEF system warning codes and fails
 ✅ Remanufactured with warranty (1 million miles / 1 year in many cases)

Applications
Ideal for use with Navistar / International trucks and IC Bus models powered by N9, N10, N13, or DT engines in the 2011‑2016 range. Used heavily in transit, shuttle, vocational, and fleet applications where DEF level sensing and emissions control are required.

Installation Notes
Have a qualified technician install this unit. Depressurize or isolate the DEF tank first. Clean the tank opening surface and inspect old seals or O‑rings. Replace seals, torque fasteners to OEM specifications. After installation, verify correct sensor outputs, clear any DEF system codes, and monitor system behavior to ensure proper function.

Final Thoughts
If your International / IC Bus is showing DEF warning lights, level sensor faults, or you’re performing DEF system maintenance, the OEM 2523590C91 DEF Head Unit is your solution for restoring reliable, factory‑accurate DEF level sensing—helping keep your emissions system working right and your vehicle road‑ready.