My 52 plate wrx has recently developed the big end knock (Only at initial start up and goes within five to ten seconds) Usually on cold mornings.
Can any one tell me if i remove the sump will it give me access to the crank in order to check for play on the bearings or rods, Also i live on a hill which makes me think is it just the oil not circulating or oil pump problem,Any info or suggestions would be appreciated .

 

Removing the sump is not enough to access the bearings adequately due to the boxer design. The conrod and crankshaft do not 'hang down' like in inline engines and are tucked into a tiny space above the sump. Better to remove the engine and split the block. You would have to measure the bearings with plastigauge, not by feeling for play.

Are you sure it's not valve noise you're hearing? Sometimes valves are noisy till oil gets to them, start the engine with someone listening and hear which end of the engine it comes from. If it's the center of the engine then maybe it might be big ends.

 

As you said you park it on a hill, and i believe the lifters on them are hydraulic therefore might be starving of oil on initial startup.

Me personally i wouldn't worry about it, especially if it's only 10 seconds worth.

Plus you may wana check for swarf in your oil if you think the bearings have gone because that;s where it all ends up.

Baly

 

most likely a lifter or cambelt tensioner... I would get it checked as if the tensioner fails the bye bye engine.

if it were a bigend it would continue when engine is hot

 

When my big end went it was quiet when it was cold. Only when the engine got up to temp and you reved it above 2500 rpm could you hear it knocking.
I wolud suspect your fault is elsewere.

 

How long does it take for the Oil light to go out and does the noise stop as the light goes out ??
As JGM said - big end knock would be there all the time.
The Lifters would be the shimmed or selective bucket type and not Hydraulic.
The Cam belt tensioner would be the first thing to check IMHO

Mick

 

When mine done this it turned out to be the tensioner, so i replaced cambelt and tensioner problem sorted. Hope your's turns out to be the same mate.