Engine Sound...

[soongster]

theres a rattling sound when i start my engine cold, .. when the engine heats up its gone...why? sounds like pistons hitting sth.. not sure how to explain what it sounds like.. i dont think its normal.. is it?

[r32woohoo]

your oil could be too thick for the cold weather and its not getting pumped around quick enough

[Yawn]

Has your engine got forged pistons?

[soongster]

i use valvoline full syn 10W 40 0r 50 i think.. cant really remember. and my engines all stock inside.

[Wacky Dee]

I've got the same thing happening on my 34 gtt and I think I know what it is. Once I took the car for a dyno and the wastegate actuator got stuck open (so wasnt making any boost) so the mechanic had to take the actuator metal cover off to fix it.

Ever since I've noticed a crappy rattle sound when the car is cold and recently tried to figure out where its coming from and I am 99% sure it's just the wategate actuator metal cover because the mechanic only put 2 screws back in and not all 4 GRRR.. so when the engine is cold it resonates and the cover makes the rattle sound but once it warms up (and components expend a fraction of a milimeter) the cover no longer rattles as it then sits tight. Im gonna have to try and source the right screws for the actuator cover to test this theory.

[soongster]

the thing is i never touched my waste gate thingy.. cos i dont know where it is... is it somewhere near the turbo heat shield?

[Wacky Dee]

it may not be exactly the same thing but it could be something silly like that .. a screw loose somewhere and when the car is cold a small space appears so that it rattles due to the vibrations of the engine. I'd try and pinpoint the source of the noiuse with someone's help.

[Justlikemusic]

Agreed... I got the same thing in my 325. Definately doesn't sound like an engine knock, but the thrust bearing and clutch is rooted and I didn't drive it enough to worry about it until I took it off the road.

[UOC]

Sounds like piston slap. When your engine is cold the pistons are smaller thus have more clearance in the bore. When u get some heat into the engine they expand @ the skirt of the piston and take up some of the clearance, thus less rattle. Could also be gudgeon pin to piston clearance or conrod bearing clearance. Does it sound uniform thru the engine or do u think its could be localised to 1 cylinder? If u think it is 1 cylinder only, remove the spark plug lead while the engine is running and see if the knock disappears or changes pitch. If it does then it is more likely to be a conrod bearing or gudgeon pin problem rather than piston slap. The vt commodore with the Gen3 was bad for piston slap when cold,a lot of the problem with then was attributed to the short piston skirt.

[soongster]

thanks, ill check for all these when i got the time. any other possible reasons? cheers,

soong.

[UOC]

just noticed u r in claremont? im in mackay, if u over this way PM me and will have a listen for ya

Ken