The Subaru 4 cylinder 2.5 L "Boxer engine" has had numerous problems with head gasket (HG) coolant leaks.
The HG problems are outlined on the website http://use...asket.html
1. The HG leaks occur in 2.5 L engines manufactured since 1996. Subaru claims the problem was corrected after 2002, but complaints are still being made on later models.
2. The 1996 to 1999 2.5 L Dual Overhead Cam engine had an inadequately designed HG which often failed early in the life of the engine. The failure allowed coolant leakage into the cylinders, which often went undetected and resulted in over heating and engine failure.
3. The 1999 to present 2.5 L engine has a Single Overhead Cam. This engine also had, and may still have, an inadequately designed HG which fails early in the life of the engine. In this engine, the failure allows external coolant leakage, which can also result in over heating and engine failure.
4. Subaru recognized the HG problem in the 2.5 L SOC engines and in April 2002 implemented a "Service Campaign" to "fix" the problem, which Subaru claims only occurred in 1999 to 2002 model years. It is clear that the inadequate design of the head gaskets resulted in early external coolant leakage failures in numerous vehicles.
5. The "Service Campaign" for the 1999 to 2002 2.5 L SOC engine consisted of adding "Genuine Cooling System Conditioner" (i.e. stop leak) to the coolant and extending the engine warranty to 8 years or 100,000 miles.
I have a 2000 Subaru Outback Wagon with the 2.5 L SOC engine.
When I received Service Campaign bulletin in April 2002, I had the dealer add the "Genuine Cooling System Conditioner" to my cooling system.
However, now at approximately 114,000 miles, coolant is profusely leaking through the poorly designed head gaskets.
1. The coolant leakage problem that occurs in 2.5 L Subaru engines is a result of inadequately/poorly designed head gaskets.
2. Without intervention, at least one head gasket in the 2.5 L engine is expected to fail in the life of nearly all 1999 to 2002 vehicles (estimated 90%probability at 100,000 miles).
3. Essentially, the head gasket failure is the result of an initial design flaw that manifests as a "latent failure".
4. The addition of the "Genuine Cooling System Conditioner" simply delays the failure of the inherent design flaw.
5. If a failure occurs after 8 years/100,000 miles, Subaru does not take responsibility for head gasket leaks.
6. The design flaw was inherent in the 2.5 L engine at the time it was manufactured. The design flaw results in a latent failure of one/both of the head gaskets. Adding "Genuine Cooling System Conditioner", as directed by Subaru, simply delays the HG failure and covers-up the fact that the 2.5 L engine is inherently unreliable.
7. The cost to repair this failure is approximately $1,500, assuming no internal engine damage. Nearly every Subaru vehicle with this design flaw will need to make this repair. Approximately 385,000 vehicles were in the "Genuine Cooling System Conditioner" (WP99) recall. At $1,500/vehicle, that's a total cost to consumers of nearly $600 million.
Subaru has masked the problem by having owners add stop leak as a temporary "fix" to a serious reliability problem.
This has resulted in very large costs to Subaru owners who must pay for repairs that resulted from a time zero design defect.