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Engine Sound...

soongster

By soongster,
in General Maintenance

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Wacky Dee Veteran

Wacky Dee

Posted
Posted

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.

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Wacky Dee Veteran

Wacky Dee

Posted
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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.

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UOC Rookie

UOC

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Posted

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.

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