mmarshall

Although he sometimes speaks in a quite-rapid manner, I like this comprehensive video, from speedkar, on why some Subaru flat-four (Boxer) engines have had head-gasket and oil-consumption problems. I had an 2.5L non-turbo Outback myself, for almost six years, and, fortunately, avoided the well-known head-gasket problems...but I am religious about oil-changes, and didn't put a huge number of miles on it despite the fact that it was almost 6 years old. But, during the period I owned it, besides the usual brakes/tires, which are normal-maintenance items, it did have one premature-failure.......particularly the electric engine-cooling fan, which caused erratic heating-up.

However, apart from the engine, the Symmetrical AWD system that Subaru uses (there are actually several different types, depending on the specific engine-transmission combination) is arguably the industry's best for car-based AWD.....simple, reliable, and efficient. Other car-based systems, like Acura's SH-AWD system and Audi's Quattro, are sometimes more sophisticated, but no one has been able to design a more simple/efficient system than Subaru, perfectly-matched to the Boxer engines.

AJT123

Thanks for the share! I love watching engine teardowns.

mmarshall

Speedkar is very thorough in his mechanically-inclined videos, and doesn't leave anything out.

Och

iTrader: (3)

There is one thing that I could never comprehend, how come there was a class action lawsuit against Toyota for the 3.0 V6 engines that developed sludge when owners severely neglected these motors and did not change oil, and yet Subaru and other manufacturers are getting away with engines and other components that are clearly defective. Honda transmissions in almost all of their V6 vehicles from late 90ies to mid 2000s come to mind.

Felix

For whatever reason theres no issues w/ the 3L or the 3.6 six cylinder engines as IK......

mmarshall

Speedkar can probably answer that one better than me, but one difference is that, from what I understand, they use head-gaskets from another contractor, with different materials. The addition of two extra cylinders also makes the engine run smoother, despite the naturally-harmonic boxer-configuration, so that means less stress and vibration on the block and heads.

timmy0tool

iTrader: (7)

my guess is that there are not as many H6 models out there to mount a big issue, plus those models are mated to a standard 5-speed AT only so there is no CVT to deal with there either. CVTs have problems too!

speedkar did a very good video on CVTs as well! he is a member here too!

LeX2K

The flat 6 engines use a MLS style head gasket, as do some of the turbo models.