Citroen C4 Radiator: Specs, Fitment & Common Faults

On the C4, a genuinely specific detail before DIY thermostat housing work: real torque figures that prevent over-tightening from causing the exact leak you're trying to fix.

Generation covered: this guide is for the current C4 (launched 2021, facelifted 2024), with particular focus on 2021–2023 registered examples now old enough for parts to be a common search. Check your logbook or VIN if you're unsure which generation you have.

Illustration for editorial purposes

A Genuinely Specific Detail Worth Knowing Before DIY Thermostat Housing Work

If you're replacing the thermostat housing yourself, it's genuinely worth knowing a specific detail that catches many DIYers out: on several engines in this range, the housing is secured directly onto the cylinder head with a thin bead of RTV sealant rather than a conventional gasket, using a relatively large number of bolts (commonly 8) tightened to a comparatively light torque figure — documented at around 8Nm on some engines — rather than fewer bolts at high clamping force. Over-tightening these bolts, assuming a higher torque figure "seems safer," can actually crack the housing or distort its sealing surface, causing exactly the leak you were trying to fix. Confirming the genuine torque specification and sealing method for your specific engine before starting is worth doing rather than guessing.

A genuinely distinct leak point worth checking separately: the corrugated rubber pipe connecting the water pump to the thermostat housing, which runs behind the engine, is a separate, well-documented leak point in its own right — distinct from the housing or pump themselves. If you've replaced the housing and pump but coolant is still disappearing, this specific pipe is worth checking directly before assuming a more complex fault.

It's also worth knowing that a genuine air lock trapped in the system after any coolant work is a common cause of the same overheating symptoms as a faulty thermostat or pump — always follow the correct bleeding procedure for your specific engine after any repair in this area.

The Part That Keeps Everything Else From Cooking

Nothing about this component is glamorous, but almost every serious engine failure that isn't wear-related traces back to a cooling system problem left unaddressed. Catching the early signs here is genuinely cheap insurance against a much bigger bill.

Before you buy: radiator size and design vary significantly by engine size, transmission type, and whether your car has air conditioning. Always confirm against your VIN before ordering.

OEM Part Numbers

Accuracy note: we weren't able to verify a confident C4-specific radiator part number at the time of writing. Please confirm the correct part via a Citroen dealer or parts specialist using your VIN.

Radiator specification varies significantly between petrol/mild-hybrid and fully electric ë-C4 versions — the electric version uses an entirely different cooling architecture for its battery and motor rather than a conventional engine radiator. Confirm your exact powertrain before ordering.

What It Does

The radiator transfers heat from the engine coolant to the surrounding air, keeping engine temperature within a safe operating range. On automatic versions, it often also cools transmission fluid through a separate internal circuit — one more reason the correct part number matters so much here.

Fitment & Compatibility

Radiators differ between manual and automatic versions of the C4 due to the transmission cooling circuit, and again across different generations. A radiator designed for a manual gearbox car will not correctly cool an automatic's transmission fluid even if it physically fits the mounting points. Always confirm the exact part number for your specific engine and transmission combination. Whether you're sourcing a replacement radiator for your Citroen C4 from a dealer, specialist, or online marketplace, always check compatibility against your registration or VIN before buying.

Common Faults

Symptoms of Failure

Engine temperature gauge creeping up — often the earliest sign, especially noticeable in slow traffic or on long motorway runs.
Sweet-smelling smoke from the engine bay — a strong indicator of a coolant leak, usually from a cracked radiator tank or failed seal.
Visible coolant puddles under the front of the car — points to a leak that needs tracing back to its source before it causes overheating.
Milky discolouration in the coolant reservoir — can indicate a more serious internal issue where coolant and oil are mixing, requiring urgent inspection.

DIY Replacement Difficulty

This is a moderate-to-difficult DIY job, typically involving draining the cooling system, removing the front bumper or grille on some model years for access, and correctly bleeding air from the system afterward. Getting the bleed process wrong can cause airlocks that mimic a still-faulty radiator, so this is one job where following the exact procedure matters. Expect 2–3 hours for an experienced home mechanic, or roughly 1–1.5 hours of labour at a garage.

OEM vs. Aftermarket

OEM radiators are generally the safer choice given how directly this part affects engine longevity, though reputable aftermarket brands with genuine OEM-equivalent specifications are a reasonable, cheaper alternative. Budget unbranded radiators are where most repeat-failure complaints cluster — this is not a part worth cutting corners on.

More Citroen Radiator Guides

The same part, covered across other Citroen models.