Parts for your 2004 Mitsubishi Lancer-Oil seals

2004 Mitsubishi Lancer oil seals: what they do and when to replace

Oil seals are absolutely used on the 2004 Mitsubishi Lancer. Mitsubishi’s factory Service Manual for the CH/CS series (2003–2007) specifies front and rear crankshaft oil seals, camshaft seals, and transaxle/drive‑shaft output seals for the 4G18/4G93/4G94 engines and F5M42/F4A4x gearboxes. The Mitsubishi ASA electronic parts catalogue likewise lists those seals as replaceable service parts. That means any engine or gearbox oil seen outside its housings has passed a failed seal, not a designed vent.

In a nutshell, oil seals keep lubricants in and grit out, so rotating shafts can spin for years without chewing out bearings. Up front, the crank seal sits behind the harmonic balancer, out back, the rear main seals the crank where it meets the flywheel or flex‑plate. Camshaft seals sit behind the timing covers. In the transmission, the driveshaft seals hold fluid where the CVs slide in. When these harden or groove, leaks start.

Best practice is to inspect for weeping at every service and budget seal replacement with timing belt or clutch work, because labour overlaps. On belt‑driven Lancers, replacing the cam and front crank seals when the timing belt is off saves time. The rear main is typically done with a clutch or rear mainplate job. Gearbox output seals are easy when CVs are out for boots or bearing work, and fresh trans fluid finishes the job.

Signs it’s time for new seals and handy checks:

• Fresh oil mist around the crank pulley or timing cover after a run, plus a flicked line of oil on the crossmember.
• Burning‑oil whiff from the exhaust side as seepage hits a hot manifold or downpipe, often with light smoke on cold starts.
• Drips at the bellhousing split line hint at a rear main leak, persistent clutch shudder or slip can follow if it’s bad.
• Manual or auto trans fluid weeping where the CVs enter the case, plus damp inner rims, points to tired output shaft seals.
• Low oil or ATF level between services without an obvious puddle usually means a slow seep—don’t wait until it becomes a gush.

Use quality seals, proper tools, and torque specs for longevity.

How much does it cost to replace a rear main seal on a 2004 Lancer?

It’s mostly labour. In Australia or New Zealand, expect roughly AUD/NZD $700–$1,400 at a workshop, depending on manual vs auto and local rates. The seal itself is inexpensive, access drives the cost.

If pairing the job with a clutch (manual) or flex‑plate/torque converter work (auto), it’s often cheaper overall because the gearbox is already out.

Can oil seals be replaced without removing the timing belt?

Camshaft and front crank seals on belt‑driven 4G‑series Lancers generally require the timing belt and related covers off. That’s why they’re commonly done during a scheduled belt change. The rear main and gearbox output seals don’t involve the timing belt.

Which engine oils help prevent seal leaks in a 2004 Lancer?

Stick to the correct grade and spec recommended for the engine and climate (commonly 5W‑30 or 10W‑40). Regular changes keep additive packs healthy and seals conditioned. Avoid “seal swell” quick‑fixes unless it’s a temporary measure—proper replacement is the reliable cure. A healthy PCV system also reduces crankcase pressure that can push oil past seals.