Many times at Sorenson Automotive, Inc. | IND. Subaru Mechanics Minnesota, Servicing South Dakota, Iowa & Wisconsin. Our Subaru Specialty Engine Repair & Rebuilding Shop we see many Subaru WRX STI as well as Outback XT's, Forester XT's, Legacy GT's, that get towed in D.O.A. usually from the Subaru Dealership that are burning oil, knocking or completely seized up caused by a failed TD04 | RHF55 VF38 | VF48 or VF52 Turbocharger Assembly. The High Velocity Air Compressor and the Turbo bearings/bushings that are inside it has given up on life and decided to "grenade" itself into your engine causing a laundry list of problems.... Or has it?... What happened? Who's fault is it and whom shall we point fingers at? Very rarely do low mileage (in service), freshly rebuilt or brand new Turbochargers fail on their own unless the work preformed during the Turbo rebuild or internal parts installed were faulty or from pre-existing manufacturer defects. 9|10 Times when a Subaru WRX gets towed into our shop with a blown up turbo it is because of 1 reason: Oil Starvation. The Turbo's lifeline of precious oil is supplied v.i.a a small oil line connected to the passenger side cylinder head and bolted down with Banjo bolts that allow oil to flow through the head, into the bolt and through the pipe. However, located in these banjo bolts (2) are small micro filters that are meant to filter out any debris coming into the turbo. These filters are recommended to be inspected/replaced every other oil change. There is very little documentation on the subject but can be found on the Subaru Tech Authority Technician Inspection Worksheet.
Needless to say this "inspection" never gets completed by the technician and addressed to the customer. These Turbo Banjo Bolts are located underneath the intake and on the rear of the cylinder head making this a 6 hour job or a $900 Oil Change. Subaru's TECH RECCOMENDATION is to remove the Banjo Screens and call it a day.
So with all the banjo bolts micro filters get plugged. The turbo gets starved of oil, the brass turbo support bushings engorge allowing the turbine shaft assembly to "walk". As the assembly walks the compressor impeller and turbine exhaust fins make contact with their turbine housings. At this point think of some little mechanic inside of your turbo with a cut off wheel and a sawzall going to town, sparks are flying, metal Is everywhere and its all getting sucked into your engine!..... If your lucky and you catch it early enough (during the oil burning stage) and you may save yourself a few thousand dollars by not having the cam journals in the cylinder head ruined, forcing you to purchase costly B25, D25 or W25 Cylinder Head Castings but at the end of the day the worst kind of damage has been done: Engine Contamination, and you can flush it all day long but its NEVER going to come out of there.
But why are the screens plugged?!.......Cheap Oil Filters, Lack of Oil Changes, Engine Connecting Rod or Main Bearing material that has unmarried itself from its other half caused by lack of maintenance, damage caused by over fueling, tiny amounts of coolant being in the crank case because of a Subaru Turbo 770 Head Gasket 11044AA770 that has failed. The list goes on and on but the point is: There is an underlying condition that exists. We have seen it all to many times where at: (The Oil Burning Stage) many inexperienced repair shops, even Subaru Dealerships will sell the Customer on a new RHF55 Turbocharger Assembly just for the vehicle to come back into the shop 3 weeks later with a seized engine. The only way to properly correct this problem is to rebuild or find a replacement Subaru WRX Engine & Rebuild the WRX Turbo
Change your Oil every 3,000-3500 Miles.
Use High Quality Oil Filters.
Use High Quality Full Synthetic Oil.
Delete the Turbo Banjo Screens Permanently or Replace them Regularly.
Love your Subaru WRX STI