Hey guys, I'm helping a friend whose engine has failed in his recently bought 2000 Subaru Legacy RSK B4. The car has an EJ20 twin turbo with no mods (mod history is unknown), 90kish miles. Recently serviced.

There was no sign of anything wrong with the car before and just after the purchase. After some heavier than average throttle use (but nothing that harsh) the engine started knocking/making noise on acceleration.

There is some damage to the intake side of the primary (the smaller first stage) turbine wheel, just the outer edge of the wheel (forgot to take a pic sorry). There's no evidence that anything made it past the wheel into the engine.

There are obvious signs of damage to the #3 piston and #3 cylinder wall. See pictures:

The valves: Look good.


The top of the piston: Looks good, no sign of foreign matter entering.


Side of piston #3:


The other side of piston #3:


The side of cylinder #3:


So far he's only been told what the problem is, not what caused it.

Any guesses are appreciated, thanks guys.

 

did he run it out of oil? or when the turbo pooped did the seals go an push the oil into the exhaust side and drop oil pressure?

 

Thanks for the response. Oil level was fine, it was checked by the warranty claims assessor and wasn't deemed responsible.

The damage to the turbine wheel fins was just superficial and the mechanic who dismantled the engine thinks that it was possible the damage may have been there when the turbo was installed (it has markings on it that imply it has come from a parted out car and has replaced the factory turbo).

The turbo has not been disassembled, is it possible the seals popped and dropped the oil pressure without obvious signs of failure? Would that cause low oil pressure in the engine as well or just the turbo?

 

[QUOTE=AndyCT9W;10534009
The turbo has not been disassembled, is it possible the seals popped and dropped the oil pressure without obvious signs of failure? Would that cause low oil pressure in the engine as well or just the turbo?[/QUOTE]

IDK if it could drop enough to not have the exhaust filled with oil and since it still had plenty of oil in it when this happened it seems unlikely. If the oil pump took a dumper, which looking at it now and reading it over again... id be looking at that. Something as simple as a bulb being blown for the low oil pressure light would keep that an unfortunate secret. It's weird that it only happened to one cylinder but anything can happen when it goes that fast.

 

If I remember correctly from my Subaru days, the #3 cylinder was always the first one to go due to it being the furthest down the fuel rail. Alot of people have had the #3 go from lean conditions.

 

Which can cause it to overheat and make the piston heat up enough to contact with the cylinder wall?

 

IDK, possible detonation, lost rings.