CriticalVery commonEngine

Subaru STI: EJ20 Phase 1 Head Gasket Failure (GC/GF 2.0T)

EJ20 Phase 1 Head Gasket Failure (GC/GF 2.0T) is a very common engine fault on the Subaru STI on the 1994–2000 cars, and we rate it critical. Putting it right costs $1,800 to $3,800 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 32 documented faults on the Subaru STI.

Vehicle: Subaru STI
Engine: EJ20
Years: 1994–2000
Fuel: petrol
System: Engine

This page covers the Subaru STI as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Subaru STI faults32 documented faults on this model

What you are looking at

What goes wrong

The first-generation EJ20 turbo uses a single-layer metal shim head gasket poorly suited to the thermal cycling of turbocharged use, leading to coolant and combustion gas leaks predominantly between cylinders 2 and 3. Failure is accelerated by overheating events, deferred coolant flushes, or sustained boost use. Consequences range from coolant loss and white exhaust smoke to catastrophic hydro-lock if coolant enters a cylinder. This is considered near-universal on unmodified high-kilometre GC/GF examples and is one of the most extensively documented faults across all Subaru WRX forums worldwide.

What you would notice

White or sweet-smelling exhaust smoke when warmed up
Coolant loss with no visible external leak
Milky or frothy residue on oil dipstick or filler cap
Overheating gauge fluctuation under load
Bubbles or oily scum in coolant reservoir

How to check it

Where to look. Cylinder head mating faces on the EJ20 flat-four, most commonly between cylinders 2 and 3 (centre of the engine)

Check the coolant overflow bottle for brown oily scum at the waterline.
Run the engine to full operating temperature and watch for white exhaust smoke.
A block-tester (combustion gas) check on the coolant reservoir is the most definitive test.
Remove the oil filler cap and dipstick and look for milky or caramel-coloured residue indicating coolant contamination.

Parts involved: Head gasket.

What it costs to put right

$1,800 to $3,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has the head gasket been replaced? If so, what specification gasket was used — single-layer OEM or multi-layer steel?”
“Has the coolant been flushed on schedule, and what is the coolant age?”
“Has the car ever overheated, even briefly?”

Now check the Subaru STI you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Subaru STI buyer questions

Is ej20 phase 1 head gasket failure (gc/gf 2.0t) serious on a Subaru STI?

We rate it critical and very common on the Subaru STI. The first-generation EJ20 turbo uses a single-layer metal shim head gasket poorly suited to the thermal cycling of turbocharged use, leading to coolant and combustion gas leaks predominantly between cylinders 2 and 3. Failure is accelerated by overheating events, deferred coolant flushes, or sustained boost use. Consequences range from coolant loss and white exhaust smoke to catastrophic hydro-lock if coolant enters a cylinder. This is considered near-universal on unmodified high-kilometre GC/GF examples and is one of the most extensively documented faults across all Subaru WRX forums worldwide.

How much does it cost to fix on a Subaru STI?

$1,800 to $3,800 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Subaru STI years are affected?

Our research records this fault on the 1994–2000 Subaru STI. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Check the coolant overflow bottle for brown oily scum at the waterline. Run the engine to full operating temperature and watch for white exhaust smoke. A block-tester (combustion gas) check on the coolant reservoir is the most definitive test. Remove the oil filler cap and dipstick and look for milky or caramel-coloured residue indicating coolant contamination. Look here: Cylinder head mating faces on the EJ20 flat-four, most commonly between cylinders 2 and 3 (centre of the engine)