Parts for your 2004 Subaru Impreza-Oil seals

2004 Subaru Impreza Oil Seals: What They Do and When to Replace

Oil seals are absolutely used on the 2004 Subaru Impreza. The Subaru Factory Service Manual for the 2004 Impreza (EJ20/EJ25) lists crankshaft front and rear oil seals, camshaft oil seals, oil pump seal, and transmission/differential axle/output oil seals in its engine and driveline sections. Subaru’s global parts catalogue (FAST) and dealer parts listings back this up with common EJ-series part numbers such as the front crank oil seal (often 806733030), camshaft oil seal (often 806732150), and rear main seal (often 806786040). So yes—oil seals are a key part of keeping this boxer engine and its driveline tidy and leak-free.

On a 2004 Impreza, oil seals keep engine oil and gear oil where they belong while letting rotating shafts spin freely. Up front, the crank and cam seals sit behind the timing covers, at the back, the rear main seal sits around the crank at the bellhousing, and in the driveline, axle/output seals keep gear oil inside the transmission and differentials. When they harden or wear, oil weeps turn into leaks, leading to mess, odours, and low oil levels.

Best practice for these Subarus is to consider the front crank and camshaft seals during the timing belt service interval (commonly around 100,000–105,000 km or time-based, per local schedule). Many techs replace them preventatively while the belt, tensioners, and water pump are off—it’s efficient and saves a second teardown later. Rear main seals are usually tackled only if there’s evidence of leakage, typically when the gearbox is out for a clutch. Axle and output seals are replaced when there’s gear oil at the stubs or backing plates, or while shafts are removed.

Handy tips the workshop crew follows:

• Use genuine-quality seals and a proper driver to set depth squarely, don’t nick the lip.
• Lightly oil the seal lip and inspect the shaft surface for wear, use a sleeve if needed.
• Clean breather/PCV systems—excess crankcase pressure can push new seals to leak.
• Verify torque specs and orientation from the Subaru service manual.

Tell-tales on a 2004 Impreza include oil mist inside the timing cover, drips at the bellhousing, or gear oil around axle stubs. If there’s a burning oil smell on the headers or fresh oil under the car after parking, it’s time for a look under the bonnet and, if needed, fresh seals.

Popular questions about 2004 Subaru Impreza oil seals

Which oil seals fail most often on a 2004 Impreza?
Common culprits are the front crank and camshaft seals (they sit behind the timing covers), especially if the timing belt service is overdue. On higher‑km cars, axle/output seals at the transmission or rear diff can also weep.

Should oil seals be replaced at every timing belt change?
It’s not mandatory if there’s no sign of leakage, but many technicians recommend replacing the front crank and cam seals preventatively during the timing belt job because access is already open and labour overlap is high.

Are OEM oil seals worth it?
For EJ engines, quality matters. OEM or high‑quality equivalents typically fit better, last longer, and are less prone to weeping, especially where shaft surfaces have minor wear.