Parts for your 2017 Mitsubishi Eclipse cross-Thermostat housing

2017 Mitsubishi Eclipse Cross Thermostat Housing: What It Does and When to Replace It

Yes, a thermostat housing is fitted to the 2017 Mitsubishi Eclipse Cross. Technical sources such as the Mitsubishi Motors workshop manual for the Eclipse Cross (GK/GL platform, 2017 launch) and the Mitsubishi ASA electronic parts catalogue detail a thermostat housed within a bolt-on water outlet assembly for the 1.5L MIVEC turbo (4B40) engine. This composite housing mounts to the cylinder head, routes coolant to the radiator and heater core, and typically carries the engine coolant temperature sensor and hose connections.

On this Eclipse Cross, the thermostat’s job is straightforward: it regulates coolant flow so the engine warms up quickly and then holds a stable operating temperature. The housing keeps the thermostat correctly located, seals the coolant passage with an O-ring or gasket, and provides the ports for the upper radiator hose and bypass circuits. When everything’s spot on, the cabin warms up promptly, the temp gauge sits steady, and fuel economy stays tidy.

Owners will usually leave the housing alone until there’s a drama. It’s not a scheduled service item, but it can need attention with age or high kilometres. Telltale signs include slow warm-up on cold mornings, overheating under load, fluctuating temp readings, a heater that never quite gets toasty, fans running all the time, or a check engine light with a P0128-style code. Coolant weeping around the housing seam or hose stubs also points to a perished O-ring or a warped/cracked housing.

When replacing, many workshops opt for the complete thermostat and housing assembly to avoid mix-and-match sealing issues. Under the bonnet, allow the engine to cool fully, drain the coolant neatly, remove the intake ducting if needed, mark hose positions, and replace the O-ring or gasket every time. Refill with Mitsubishi Super Long Life Coolant (blue) at the correct concentration using demineralised water if topping from concentrate, then bleed air from the system per the workshop manual. Always torque the housing bolts to the spec in the service manual to avoid warping the composite body.

Good practice while you’re in there:

• Inspect hoses and clamps, replace any that are swollen, brittle or corroded.
• Check the ECT sensor and connector if it’s mounted in the housing.
• Pressure-test the cooling system after refilling to confirm a proper seal.

With quality parts and a proper bleed, the Eclipse Cross cooling system should run sweet for years.

Popular questions

Where is the thermostat housing on a 2017 Eclipse Cross?
It sits at the cylinder head’s outlet side, under the bonnet on the left-hand side of the engine bay (as you face the car), where the upper radiator hose connects. The assembly is a composite water outlet that also carries the temperature sensor and hose stubs.

Do I need to replace the whole housing or just the thermostat?
Many versions use an integrated thermostat-and-housing assembly with a dedicated O-ring. If the housing is warped, cracked, or the hose seats are pitted, replace the full unit. If the design allows a separate thermostat and the housing is in top nick, the thermostat and seal may be replaced on their own.

What coolant should be used after replacement?
Use Mitsubishi Super Long Life Coolant (blue). If using concentrate, mix with demineralised water to the correct ratio. After refilling, bleed the system as per the workshop manual so no air pockets remain.