Hi Guys could someone explain to me what Knocking is. I've just had a new clutch fitted at Foresters (good job done) and Ivan said that he could hear that the crank was on its way out as there is a slight knocking sound that you can hear up to about 2500 revs when cold but then dissapears. Should i be cacking myself as i like to drive pretty hard.
Cheers

 

There are two types, knocking or detonation which is the fuel mixture being ignitied before it should which could lead to melted pistons if left untreated and big end knocking which you've probably got. This is due to wear on the big end crankshaft bearings and means it's rebuild time, you may get away with a crank regrind and new shells but not really worth it on a performance car especially one driven hard. Get it checked out, if it is the big ends and you ignore it your crankshaft and pistons will pop out to say hello.

 

Could also be piston slap if it's audible when the engine's cold but goes away as it warms up. What model year is your car Eddy?

 

Thanks guys, It's a 1997 wrx import decat and induction kit fitted. The sound gets less audible as the engine warms but i'm kidding myself that it actually goes away. Can't afford a rebuild at moment will it last another 6 months i wonder?