I have been reading through the Subaru site about the various engines and am not sure what I have as 1, it's at the mecahnics and 2, it's in pieces. The vin says it's a 2.5L H4 DOHC 16V. Is this a turbo or not?

in the USA, the turbocharged 2.5L came in 2004 via the 2004 STI. The WRX got the 2.5L turbo in 2006 onwards.

 

 

If it is the DOHC 1996-1999, it is naturally aspirated, and the one known to be very likely to blow head gaskets.

 

Note that this applies only to US market Subarus. I do not know if any of this information applies to other regions.

If replaced, will this reduce repeated issues?

If replaced, will this reduce repeated issues?

 

It is entirely dependent on how soon the blown headgaskets are diagnosed. If they were discovered late, you are better off buying a new engine, as it seems those who replace it after a relatively late diagnosis may have major engine troubles in the long run. Supposedly, the bearings do not like coolant, and the coolant puts exponentially-higher wear on the bearings.

It is almost common practice here on USMB to replace a 2.5 with the much more reliable 2.2.

 

If diagnosed immediately, replace with Subaru OEM head gaskets as others seem to have issues with aftermarket gaskets.

 

 

Note this is advice from someone who reads Subaru forums, not one who actually does work on Subarus.

The 25D head gaskets do not mix coolant and oil. But that engine does suffer from higher than typical bottom end failure - due to overheating. Overheating breaks down the oil and causes it to of very low viscosity. If not changed promptly after an overheat there is a higher likelyhood of failure down the line. Any 25D with a blown head gasket or that has blown one in the past is suspect in my book - I generally turn them away or flat replace them with 22's.

 

The 25D is also quite a bit more expensive to maintain - from it's timing belt/tensioner arrangement, to it's DOHC heads that have silly bucket/shim valve adjustment and are typically in the $500 range to have rebuilt..... it's less reliable AND more expensive to work on..... all around not the best choice in my opinion.

 

GD