Why Subaru's Head Gaskets Became A Running Joke (And Whether It's Still Deserved)

Subaru's most reliable cars ever include old standbys the Outback and Forester along with newer models like the all-wheel drive 2024 Crosstrek. Yet despite the brand's solid reputation, Subaru became a bit of a joke some years back for its response to a serious design flaw. The problem started in the early 2000s with head gasket leaks on Subaru's 2.5-liter EJ engines. Some leaked internally, mixing engine oil and coolant while others drizzled coolant on the engine block leaving greenish streaks and a sweet smell under the hood. These leaks led to plenty of premature engine failure from overheating or insufficient lubrication. Subaru's response was not only unsatisfying for owners, but the public relations doublespeak from Subaru made some of them wonder if they were being pranked. The document in question — Subaru of America's 'owner notification letter titled Service Program WWP-99, — went out to 376,000 owners of late '90s and early 2000s Subarus with  2.5-liter engines in 2004. 

The notice instructed affected owners to visit a Subaru dealer for a free dose of Genuine Subaru Cooling System Conditioner to prevent what the automaker called a "possible small external coolant leak" at the head gaskets due to "normal expansion and contraction of [the] engine." Subaru's choice the words "small," "possible," and "normal"  was dismissive of owners' concerns and the solution seemed like a bit of legal self-protection. From there, the internet did what it does and turned Subaru's corporate spin into a long running joke. 

The special cooling system conditioner later turned out to be a relabeled version of a popular British stop-leak product. Subaru's boxer engines have been around since 1966, and the 2.5-liter EJ powered much of Subaru's lineup by the turn of the century. 

It can cost $2,000-$4,000 out of pocket to have a head gasket replacd, so if you're buying a used Subaru with this engine your first question to the seller should be if the head gasket has been upgraded. Subaru's initial response to the issue was baffling and dissatisfying to many owners; the service bulletin only mentioned the external leaks and the solution it offered was temporary at best. Owners had to bring their cars in to a service location where technicians would add the cooling system conditioner (part #SOA635071) to  stop the external leaks.

For owners in search of a permanent fix this seemed like snake oil, but the additive itself wasn't a gimmick. Based on the packaging and chemical composition it appears to be a relabeled supply of Radweld from the British auto supply company Holt Lloyd. Radweld works like similar radiator stop leak products from Bar's Leaks and Permatex; these formulas flow through coolant passages and condition seals and gaskets to stop small leaks. The bulletin even specified that the additive should be used at any future coolant drain-and-fill services.

If your car got the conditioner added while still under its original warranty, Subaru would cover external coolant leaks at the head gaskets for up to eight extra years or 100,000 miles, but there were strings attached. The extended warranty period didn't cover internal gasket leaks, overheating, head gasket replacement, or internal engine damage. And if your original warranty had expired or the 'genuine' conditioner wasn't used, you were out of luck and possibly several thousand dollars.

Although the stop-leak solution bought Subaru a little time to go with its public shaming, the company knew it needed to actually do something about the problem. Subaru began using multi-layer steel gaskets in place of the weak composite ones around 2010, and this largely fixed the infamous external leaks. Subaru then began rolling out the FA and FB engine families with revised blocks, cooling systems, and cylinder head designs. Fortunately Subaru's engineers appeared to have learned from their mistake, and the FA and FB engines never developed the same problem or reputation. 

The new engines have seen a few recalls and service bulletins for cooling-related issues, including a 2023 recall for loose water pipe bolts on the 2024 Forester and a 2022 advisory about water pump gaskets that only affected 49 cars. Subaru still lists the genuine cooling system conditioner in some service documentation; many skeptics point to this as a ghost of the old issue. In reality, the head gasket stigma is only relevant if you're buying a 20-year-old Outback and not a 2025 Forester Hybrid. The joke only remains alive because EJ-powered Subarus remain plentiful on the secondhand market and cyberspace loves a snarky trend. The internet may never drop the matter, but Subarus no longer come off the line with substandard head gaskets.