Mitsubishi ASX cooling-coil leak, early sensor cut-off and air-box foam restoration

Sifu White explains what happened

Prices, repair times and warranty terms mentioned in the video applied at the time. Ask the workshop about current arrangements.

The cooling coil for this model is genuinely expensive. Today we are discussing the Mitsubishi ASX, a model we repair frequently. Its cooling coil has started leaking. Replacement requires removal of the dashboard and air-conditioning casing, and leaks often appear in particular areas of the coil.

When replacing the cooling coil, we also advise inspecting and normally replacing the temperature sensor because it can cut off too early, before the cabin is sufficiently cold. The three items commonly recommended are the sensor, cooling coil and expansion valve. Foam seals on the air-conditioning casing also commonly deteriorate and need restoration.

Suitable foam has to be prepared and this area restored carefully. The old foam must be removed slowly, the surface cleaned and new seals installed. This is a time-consuming part of the job.

Why access and reassembly matter to the result

The evaporator usually sits inside the cabin HVAC housing. Access depends on the model, year and housing design. Some vehicles require dashboard removal; others provide a side-access route. Fewer dismantling steps are not automatically better, and more dismantling is not automatically necessary. What matters is whether the component can be reached correctly and whether clips, fasteners, wiring and seals can all be restored as intended.

Foam and duct seals keep air travelling through the intended paths. A damaged housing, missing fasteners or displaced seal can leave air leaks, noises or uneven delivery. The repair plan should therefore cover reassembly checks as well as the price of the replacement coil. Marks from earlier work may be useful clues, but glue or cracks alone do not establish who caused the damage or exactly how it happened.

Why airflow can fade during a long drive

The evaporator is the component commonly called the cooling coil. Air is cooled as it passes over it. If ice builds up on its surface, the air passage can become progressively restricted. The owner may notice strong cooling initially, then less and less air during a longer drive. That sequence is different from air continuing to blow strongly but becoming warm, and the distinction helps the technician choose relevant tests.

Temperature feedback, anti-icing control, refrigerant condition, metering and airflow can all be relevant; ice alone does not prove a sensor has failed. A problem that develops after a long run may not appear during a short idle test. Record how long it takes, the temperature and fan settings, and whether airflow returns after the system has been off for a while. Verification should cover those trigger conditions without treating unsafe driving as a diagnostic requirement.

What to tell the workshop about your own car

You do not need to guess a part name first. A clear description of what actually happens is often more useful for reproducing the complaint than requesting a particular replacement.

• Ask about access, seals, fasteners and the functions checked after reassembly.
• Record when airflow fades and whether stopping or switching A/C off changes it.
• Include the model, year, recent repairs and what changed before or after the symptom began.