ENGINE KNOCK
06 February 2007, 07:23 PM
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ENGINE KNOCK
MY DADS ENGINE ON HI 96 IMPREZA TURBO KNOCKS LOUDLY WHEN COLD AND QUIETENS DOWN WHEN ITS WARMED UP, HE HAS BEEN TOLD THAT ITS PISTON NUMBER 3 GOT BAD SLAP DOES ANYONE KNOW A CHEAP WAY OF SORTING THIS PROBLEM OUT THAT ISNT GONNA COST HIM HIS ARM AND LEG
06 February 2007, 07:31 PM
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Who says its a problem?
Piston slap is only considered a problem if it is VERY loud, or doesn't totally dissappear when warm or at the very least within 30mins of engine running, or the engine also has excessive oil consumption, or compression problems.
Like many modern engines the Impreza engine suffers piston slap when cold, just the impreza appears to be louder - partly due to sound deadning materials used and the structure of the engine. The severity of piston slap is laso depending on which piston materials and coatings that are used, aftermarket forged STi pistons for example, are notoriously loud when cold.
This is due to the metalugic composition of the materials used and their thermal properties, where the piston expands at a differing rate to the cylinder bore. Once warm, normal tolerances are achieved. Put it this way, a clearance when cold is better than zero clearance when hot.
Bottom line; ain't broke...don't fix.
Any doubts give Dave @Api a call (see adverts), if he doesn't think its broke, he won't fix it
(excepting Isuzu troopers
)
Piston slap is only considered a problem if it is VERY loud, or doesn't totally dissappear when warm or at the very least within 30mins of engine running, or the engine also has excessive oil consumption, or compression problems.
Like many modern engines the Impreza engine suffers piston slap when cold, just the impreza appears to be louder - partly due to sound deadning materials used and the structure of the engine. The severity of piston slap is laso depending on which piston materials and coatings that are used, aftermarket forged STi pistons for example, are notoriously loud when cold.
This is due to the metalugic composition of the materials used and their thermal properties, where the piston expands at a differing rate to the cylinder bore. Once warm, normal tolerances are achieved. Put it this way, a clearance when cold is better than zero clearance when hot.
Bottom line; ain't broke...don't fix.
Any doubts give Dave @Api a call (see adverts), if he doesn't think its broke, he won't fix it
(excepting Isuzu troopers
)
Last edited by Shark Man; 06 February 2007 at 07:36 PM.
07 February 2007, 11:44 AM
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Piston slap is just a noise. Until you are putting in as much oil as petrol leave it well alone.
David APi
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