have a feeling this might be bad , my rb5 has developed a knocking sounds as if its coming from the back of the engine (if stood infront of car) ans slightly to the left , have a feeling its no3 cylinder cracked does this sound right

 

Does the engine smoke at all or suffering a drop in oil pressure ??
If you gently bring the revs up to 2500rpm and release the throttle, you will hear a failed big end bearing as the revs fall.
Hopefully its not the big ends in your case.

Mick

 

that is what happens sounds like the engine over revving but with no revs if that makes sense.but no smoke or drop in oil pressure.

 

also i have dropped the oil today and there is no metal fillings in it . is this a good sign

 

sounds like piston slap if it does it when cold, if it still knocks when warm then time to inspect.

 

does it all the time loader when hot

 

definately needs looking at by a subaru specialist to determine the knocking but sounds like its time for a rebuild.