Common Problems with the
2005–2008 Proton Impian

Structural corrosion is a serious longevity issue on aging Proton Impians in the UK. The front radiator lower support panel, bumper beam support legs, and front subframe anchor points received minimal cavity wax protection and thin factory electrophoretic primer. Road salt and damp debris kicked up through the lower grille remain trapped along the double-skinned spot-welded seams. Over multiple British winters, extensive rust perforation develops unnoticed beneath the front bumper, weakening the front crash structure and causing automatic MOT test failure for structural rust within 30cm of suspension mountings.

The 1.6-litre 16V Mitsubishi 4G18 engine employs a wasted-spark ignition system featuring two coil packs mounted directly above cylinders two and four, with high-tension (HT) leads feeding cylinders one and three. Radiant cylinder head heat and minor oil seepage from the rocker cover gasket break down the dielectric silicone insulation on the coil pack extension tubes and lead boots. High voltage arcs across the spark plug recess to the engine block rather than firing the plug. This produces noticeable engine misfiring under load, hesitation when accelerating in higher gears, a flashing check engine light, and potential catalytic converter damage from unburnt fuel.

The Proton Impian's standout chassis dynamics were achieved via an independent multi-link rear suspension setup engineered in partnership with Lotus. However, the system relies on numerous rubber trailing arm bushings and spherical rose joints that suffer severe wear from UK pothole strikes and corrosive road salt. Over time, the rubber degrades, tears, and debonds from its outer steel sleeves. This allows excessive rear-wheel toe and camber deflection, resulting in rear-end instability and wandering at motorway speeds, clunking sounds over road imperfections, uneven inner rear tyre tread wear, and MOT failure.

The hydraulic power steering system on the Impian routes rigid steel hydraulic pipes across the lower front crossmember and steering rack body. In the wet British climate, road grit and salt spray thrown from the front wheels accumulate in the retaining brackets and strip the pipe coating. Severe rust pitting develops along the pipe walls, eventually causing pressurized power steering fluid to seep or spray out under pump load. In addition to creating heavy steering assistance drop-out during parking and pump whine, leaking fluid contaminates front suspension bushes and results in an MOT refusal.

The cable-driven front electric window regulators on the Proton Impian are prone to mechanical and electrical failures. Brittle molded nylon pulleys inside the door shell crack from aging, causing the braided steel drive cables to jump off their tracks, fray, and bind inside the spool housing. Furthermore, rain entering past the outer window scraper seals into the driver door card oxidizes the electrical copper contacts within the master power window switch block. This leaves window glass stuck partially open or dropping into the door cavity, requiring regulator assembly replacement.