Subaru Head Gasket Failure and Water in Oil — New Zealand Guide
Subaru EJ-series engines have a known head gasket vulnerability. Coolant in oil is a common consequence. Here is what New Zealand Subaru owners need to know.
Subaru's EJ Engine Head Gasket History
The Subaru EJ-series engine, fitted to Impreza, Legacy, Forester, and Outback models from roughly 1989 to 2012, has a well-documented head gasket vulnerability. Particularly affected are the non-turbo EJ20 and EJ25 engines from the late 1990s and early 2000s. The design uses composite multi-layer steel gaskets that are susceptible to failure between coolant and oil passages, leading to coolant contaminating the oil system.
Signs Specific to Subaru
Subaru coolant-in-oil can be subtle at first. Look for: a slight sweet smell from the engine bay; oil filler cap with a grey milky residue inside; coolant level dropping slowly with no visible external leak; and a slight white haze in the exhaust after the engine warms up. By the time the dipstick shows obviously milky oil, the contamination is typically significant.
Cost of Running on Contaminated Oil
The EJ engine has aluminium cylinders with a cast-iron liner — the bearing surfaces are particularly sensitive to lubrication quality. Running the engine with coolant-contaminated oil accelerates wear on the big-end and main bearings, potentially converting a $1,200 head gasket job into a $4,000-6,000 engine rebuild.
What to Do
If your Subaru shows any of these signs, stop and call EEK Mechanical. We drain and flush the oil system, provide documentation for the mechanical repair, and can refer you to Subaru specialists experienced with EJ head gasket work.
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