Expansion Tank Cap Citroën Peugeot 1304E4

Description

Expansion tank cap for Citroën and Peugeot vehicles — 1.4 bar.

Product Overview

High-quality expansion tank (coolant reservoir) cap designed for Citroën and Peugeot cars with a 1.4 bar pressure rating. This cap maintains the correct pressure in the cooling system, prevents coolant loss and helps avoid localized boiling. Ideal for mechanics and DIY enthusiasts who need a reliable, direct-replacement cap to restore proper cooling system function.

Features and Function

• Pressure Rating: 1.4 bar — ensures the cooling system reaches its designed operating pressure before releasing excess into the overflow reservoir.
• Primary Function: Seals the coolant reservoir, maintains system pressure, allows controlled release of excess pressure, and prevents air ingress.
• Construction: Spring-loaded valve and sealing gasket designed to withstand typical engine bay temperatures and coolant chemistry.
• Fitment Type: Direct replacement for compatible Citroën/Peugeot coolant reservoirs (see Technical Information for codes).

Technical Information

• Manufacturer: Stellantis (Citroën / Peugeot)
• Model: Expansion Tank Cap / Coolant Reservoir Cap
• Product Codes: 1304E4
• Additional Numbers: 1306E4, 1306C9

Compatibility / Typical Applications

Designed for a range of Citroën and Peugeot passenger cars and light commercial vehicles that use a 1.4 bar expansion cap. Common examples include small and compact models from the Stellantis family — for instance, many variants of C2, C3, C4, 206, 207, 307, 308, Partner and Berlingo. Always check the part numbering against your vehicle build or parts catalog before fitting.

How To Replace (Basic Guide)

1. Allow the engine to cool completely. Never remove the cap from a hot, pressurized cooling system.
2. Clean the filler neck area to prevent contamination entering the system.
3. Turn the old cap counterclockwise and remove. Inspect the filler neck for corrosion, deposits or damage.
4. Compare the new cap to the old one (pressure rating, sealing surface and locking features).
5. Fit the new cap onto the filler neck and turn clockwise until it seats firmly. Some caps require a slight push-and-twist to lock.
6. Start the engine and allow it to reach operating temperature, then check for leaks and proper coolant level. Top up if necessary when cold.

Installation Recommendations

• Always replace the expansion cap when the sealing gasket or spring shows visible wear or when the cap no longer holds pressure.
• Perform replacement only when the engine is cold to avoid scalding from hot coolant.
• Inspect the coolant reservoir filler neck for damage or deformation that could prevent a proper seal.
• After installation, bleed the cooling system if air was introduced and verify correct coolant level and system pressure during a test run.
• Use genuine or OEM-equivalent caps with the correct pressure rating (1.4 bar) to maintain cooling system performance.

Why This Part Fails (Most Common Causes)

• Aged or Hardened Seal: Rubber gaskets dry out and harden over time, causing leaks or loss of pressure.
• Spring Fatigue: The internal spring can weaken, preventing the cap from maintaining the correct release pressure.
• Corrosion and Deposits: Corrosion or scale on the filler neck or cap valve seats prevents a proper seal.
• Overheating/Excessive Pressure: Repeated overheating events can damage the cap or accelerate seal deterioration.
• Incorrect Part: Using a cap with the wrong pressure rating leads to overheating or premature coolant loss.

Maintenance Tips

• Inspect the cap during routine coolant service intervals; replace at first sign of cracking, deformation or leakage.
• Use manufacturer-recommended coolant and follow service schedules to reduce internal corrosion and deposits.
• When replacing, consider also inspecting hoses and the overflow reservoir for related wear or damage.