Parts for your 2018 Mitsubishi Asx-Thermostat housing

2018 Mitsubishi ASX thermostat housing — what it does and how to look after it

Yes, the 2018 Mitsubishi ASX uses a thermostat housing. Technical references including the Mitsubishi Motors service manual (Cooling System section), the Mitsubishi ASA electronic parts catalogue, and major ANZ parts catalogues (Gates, Dayco, Repco) list a thermostat and dedicated housing for ASX models of this year, particularly the common 2.0L petrol (4B11) variant. The housing sits at the coolant inlet/outlet on the engine and secures the thermostat while routing coolant to and from the radiator.

On the 2018 ASX, the thermostat housing’s job is pretty straightforward: it holds the thermostat in the correct position, seals the coolant passage with an O‑ring or gasket, and provides the hose connections for coolant flow. Depending on engine variant, it’s typically a cast alloy or composite unit and may also carry a coolant temperature sensor or bleed point. By helping the thermostat manage operating temperature, the housing is a quiet achiever for fuel economy, heater performance, and engine longevity.

This isn’t a part that’s replaced on a time basis, but it should be inspected whenever the cooling system is serviced. Common reasons to change it include a cracked or warped body, persistent leaks at the flange, or corrosion around the hose stubs. Many owners elect to replace the housing at the same time as a new thermostat to avoid doing the job twice, especially on higher‑kilometre ASXs.

• Tell‑tale symptoms: coolant smell or drips under the front of the car, chalky pink/white residue at the housing, slow warm‑up or overheating, temp gauge wandering, or coolant loss with no obvious hose failure.
• Good servicing habits: use the correct Mitsubishi‑approved long‑life (blue) coolant, renew the thermostat O‑ring/gasket whenever the housing is opened, and pressure‑test after refilling.

When replacing, allow the engine to cool fully, drain enough coolant to drop below the housing level, remove the lower hose, unbolt the housing, and lift out the thermostat. Clean the mating surfaces carefully, fit a fresh thermostat and O‑ring, then reinstall the housing and tighten the bolts evenly to the workshop‑specified torque. Refill with the right coolant mix, bleed the system (heater on hot, engine idling, top up as bubbles purge), and check for leaks under the bonnet and at the radiator cap after a short drive. Done right, the ASX’s thermostat housing will stay leak‑free and the temperature needle will sit bang on where it should.

• Where is the thermostat housing on a 2018 ASX?
  The easiest way to find it is to follow the lower radiator hose back to the engine. Where that hose meets the engine block is the thermostat housing. It’s typically low on the engine and secured with a couple of small bolts, with the hose clamped to a short outlet.
• Do they need the whole housing or just the thermostat?
  Often, just the thermostat and O‑ring will sort issues like temperature control faults. If the housing is cracked, warped, corroded, or its hose connection is damaged, replacing the complete housing assembly is the smarter move. Many techs replace the housing at the same time on higher‑kilometre cars to prevent future leaks.
• Does the cooling system need bleeding after replacing the housing?
  Yes. Air can get trapped when the housing is opened. Refill with the specified Mitsubishi long‑life coolant, run the engine with the heater on hot, and allow air to purge. Squeezing the upper hose gently can help. Some workshops use a vacuum‑fill tool for a clean, bubble‑free result.