Parts for your 2020 Mitsubishi Asx-Heater hose

2020 Mitsubishi ASX Heater Hose – What It Does and How to Look After It

The 2020 Mitsubishi ASX is fitted with heater hoses. This is confirmed by Mitsubishi’s ASX/RVR/Outlander Sport workshop manual (Group 55A: Heating, Ventilation & Air Conditioning) and the Mitsubishi ASA electronic parts catalogue for GA-series models, both of which specify a pair of heater water hoses running between the engine and the heater core at the firewall.

On this ASX, the heater hoses carry hot engine coolant from the 2.0‑litre MIVEC engine through the heater core and back again. That loop gives the cabin warm air for demisting and winter comfort, and it helps stabilise engine temperatures on cold starts. Most 2020 ASX variants use a blend-door inside the HVAC unit rather than an external heater tap, so coolant typically flows continuously through the heater core—meaning those hoses work every time the engine runs.

As part of routine servicing, it’s smart to inspect the heater hoses along with the rest of the cooling system. Look for soft spots, cracks, glazing, swelling near the clamps, dried coolant crust, or any seepage at the firewall. Oil contamination from nearby leaks can shorten hose life, and electrochemical degradation can make an older hose feel mushy. A sweet smell, fogged windscreen, or damp carpet hints at a heater circuit issue that deserves quick attention.

Replacement is straightforward but best done on a cold engine. Expect 1–2 hours. Replace hoses as a pair, use new spring-band clamps (as per OEM practice), and refill with the correct coolant—Mitsubishi Genuine Super Long-Life Coolant (blue), mixed to spec. Bleed the system carefully: set the climate to hot, run the engine at fast idle, squeeze the upper radiator and heater hoses to purge air, and top up the reservoir as bubbles clear. Avoid twisting the heater core tubes at the firewall, support them when removing old hoses with a proper hose pick.

For timing, many techs in Australia and New Zealand recommend preventive hose replacement around 7–10 years or 150,000–200,000 km, or sooner if any ageing signs appear. Skipping a tired heater hose can lead to sudden coolant loss and an overheated engine—far costlier than a planned replacement.

• Service check: every scheduled service, or at least every 10,000–15,000 km/6–12 months.
• Tell-tales: bulges, cracks, coolant smell, damp firewall area, low coolant level.
• Best practice: replace in pairs, fit new clamps, renew coolant, bleed thoroughly.

FAQs

Does the 2020 ASX have a heater control valve?
Most 2020 ASX models for AU/NZ use an internal blend-door, not an external heater tap. Coolant generally circulates through the heater core all the time, and cabin temperature is adjusted by air-mix doors. That’s why the heater hoses see constant heat-cycling and deserve regular checks.

What coolant should be used when replacing heater hoses?
Use Mitsubishi Genuine Super Long-Life Coolant (blue) to the correct mix ratio. After fitting new hoses and clamps, refill and bleed the system with the heater on hot to clear air pockets. Sticking with the specified coolant helps protect aluminium components and hose materials.

Is it safe to drive with a leaking heater hose?
Not really. A small seep can quickly become a split, dumping coolant and risking an overheated engine. In an emergency, a temporary bypass loop can get the vehicle to a workshop, but cabin heat is lost and it’s strictly a short-term fix. Proper repair should follow promptly.