This replacement filter box (airbox) fits the 1.6 HDi 80 kW (engine code 9HZ) family used in Citroën C5 II (X7) and Peugeot 407 models. It houses the engine air filter and ensures clean, metered airflow to the engine management system and turbocharger. The part is often searched and identified by OE numbers, making it easy for professional mechanics and DIY enthusiasts to find the correct unit for service or repair.

Designed to restore proper intake sealing and reduce unwanted air leaks, this airbox helps maintain engine performance, fuel efficiency and reliable operation of the mass air flow (MAF) sensor. Replacing a damaged or cracked airbox eliminates unfiltered air ingestion and prevents related issues such as poor idling, reduced power and false air readings.

Technical Information

• Manufacturer: Stellantis (Citroën, Peugeot)
• Model: Citroën C5 II (X7); Peugeot 407 — Engine 1.6 HDi 80 kW (9HZ)
• Product Codes: 9685205580, 9651883080, 1420N9
• Other Numbers: 9648938580

Installation Recommendations

1. Park on a level surface, engage the parking brake and isolate the ignition.
2. Disconnect the negative battery terminal if you will be handling electrical connectors (recommended when removing the MAF sensor).
3. Remove the intake ducting and any sound deadening resonator attached to the airbox. Loosen hose clamps and unclip retaining fasteners.
4. If equipped, carefully unplug the MAF sensor connector and remove the sensor from the airbox housing to avoid damage. Keep screws and seals clean and reuse if undamaged.
5. Unscrew or unclip the airbox mounting points and extract the old housing. Inspect mounting rubbers, hoses and clamps; replace any brittle or damaged items.
6. Install the new airbox, refit the MAF sensor and reconnect electrical connectors, ensuring a proper seal. Reconnect intake ducts and tighten clamps securely but do not overtighten plastic fixings.
7. Fit a new air filter element at the same time for best performance and to prevent immediate contamination of the new housing.
8. Perform a visual leak check and start the engine to verify normal idling and absence of intake leaks or abnormal noises.

Why The Part Fails Most Often

• Plastic Fatigue And Heat Cycling: Long-term exposure to engine bay heat and vibration causes cracks or warped sealing surfaces.
• Impact Or Poor Handling: Damage during repairs or from road debris can break mounting tabs or create cracks.
• Clogged Or Saturated Filter Element: A neglected air filter can become saturated with dirt or oil, leading to excessive pressure differentials and stress on the housing.
• Oil Contamination Or Turbo Leaks: Oil ingress from turbocharger or PCV systems can degrade plastic and seals over time.

Maintenance And Signs Of Failure

Inspect the airbox each time you replace the air filter (typical service interval ~20,000 km under normal conditions, sooner in dusty environments). Replace the airbox if you find visible cracks, damaged mounting tabs, a compromised seal around the filter element or evidence of oil/water ingress. Common symptoms of a failing airbox include rough idle, reduced power, increased fuel consumption and inconsistent MAF readings.

Because technicians and DIY mechanics frequently look up parts by OE numbers, the listed product codes make it straightforward to confirm fitment and order the correct replacement for Citroën C5 II (X7) and Peugeot 407 1.6 HDi 80 kW (9HZ) models.

This filter box is designed for the 1.6 HDi 80 kW diesel engines used in Citroën C5 II (X7) and Peugeot 407. Ideal for mechanics and DIY enthusiasts who search by OE numbers, this replacement part restores correct air routing and protects the engine by housing the air filter element. The robust construction ensures secure mounting and reliable sealing to prevent unfiltered air ingress, which can cause performance loss and increased wear. Featuring compatible product codes listed below, the unit is a direct-fit part for affected models and simplifies workshop replacement with common tools.

Technical Information

• Manufacturer: Stellantis (Citroën / Peugeot)
• Model: Citroën C5 II (X7); Peugeot 407
• Product Codes: 9659405080; 9651883080; 1420N9
• Additional Numbers: 1.6 HDi, 80 kW

Function And Benefits

The filter box houses the engine air filter and channels intake air to the turbocharger and engine. A properly sealed filter box prevents contamination from dust, moisture and debris, helping to maintain fuel economy, throttle response and turbocharger longevity. Replacing a damaged filter box restores correct air metering and prevents unfiltered air from bypassing the filter element.

Typical Replacement Interval And Symptoms

Filter boxes do not have a fixed service interval and usually last the life of the vehicle unless damaged. Replace the unit if you notice visible cracks, broken mounting tabs, persistent check-engine lights related to intake or mass-air readings, unusual whistling from the intake, or if the airbox no longer seals properly. Addressing a faulty filter box promptly prevents accelerated wear of the air filter and downstream components.

Installation Recommendations

• Prepare basic workshop tools: screwdriver set, socket set and new clamps if required.
• Disconnect the battery if you will unclip or disconnect any sensors near the airbox to avoid accidental faults.
• Release clamps and remove intake ducts connected to the airbox; carefully unplug any sensors (e.g., MAF) if present and note their orientation.
• Remove fixing bolts or clips and lift out the old filter box with the air filter element; inspect and replace the filter element if needed.
• Fit the new filter box, ensuring all sealing surfaces and gaskets are clean and correctly seated; tighten clamps to proper torque and reconnect sensors and ducts.
• Start the engine and check for intake leaks, unusual noises and that no diagnostic warnings remain.

Why This Part Most Often Fails

• Physical Damage: Impact or improper handling can crack the housing or break mounting tabs during maintenance.
• Age And Heat Cycling: Prolonged exposure to engine heat and vibration can embrittle plastic, leading to hairline cracks and leaks.
• Poor Sealing: Worn or damaged gaskets and loose clamps allow unfiltered air ingress, causing contaminants to bypass the filter element.
• Aftermarket Modifications: Incorrectly fitted intake upgrades or clamps can stress mounting points and accelerate failure.

Pick this filter box when you require a direct-fit replacement for Citroën C5 II (X7) and Peugeot 407 1.6 HDi 80 kW applications. Use the OE product codes 9659405080, 9651883080 or 1420N9 to find the correct listing quickly and ensure compatibility with the targeted engine variant.