piston slap when cold
08 June 2003, 10:51 AM
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just brought a 97 uk 36000miles from new full subaru service history and it seems to have piston slap when cold has any one managed to get this fixed for free on a car which is this old. or dont i stand much chance.
08 June 2003, 11:12 AM
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did you buy the car private or from a dealer?
(dealers should have a warranty with the car
)
If not you could take it to a subaru dealer and see if you can get the work done as a good will gesture??
Tony
(dealers should have a warranty with the car
)If not you could take it to a subaru dealer and see if you can get the work done as a good will gesture??
Tony
08 June 2003, 03:34 PM
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Ive got it too. Dealer wants £74 for piston . £ 200 for gasket set. And £835 labour. Going to do mine myself next week will keep you posted Plus will put new clutch in at same time and rocker covers
08 June 2003, 03:46 PM
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I copied this from a previous post of mine on the MRT forums. We were discussing piston clearances.
As far as I know there isnt much you can do about piston slap except wait till the engine is warm until you give it a boot full.
Im not an expert but here goes.
If the pistons have more clearance they have more room to pivot on the gudgeon pin. Its a matter of simple geometry to work out that the shorter the Piston skirt the more it can pivot. A short skirt is a characteristic of light weight forged pistons.
The pistons are made with clearances so that when the alloy expands due to heat it will still clear the bores. However when cold the extra clearance allows the pistons to pivot and touch the bores causing the piston slap.
The rate of expansion and the amount of expansion is dependent on the Alloy. Better quality pistons (read more expensive) can have less clearance as the alloy does not expand as much when heated.
As for Nitrous they say that you should have slightly more bore clearance due to the sudden increase in power i.e. 100hp or more in a split secound can cause extra expansion in the piston.
As an aside if you give the engine a boot full when cold some blow by can occur due to the extra clearance
As far as I know there isnt much you can do about piston slap except wait till the engine is warm until you give it a boot full.
Im not an expert but here goes.
If the pistons have more clearance they have more room to pivot on the gudgeon pin. Its a matter of simple geometry to work out that the shorter the Piston skirt the more it can pivot. A short skirt is a characteristic of light weight forged pistons.
The pistons are made with clearances so that when the alloy expands due to heat it will still clear the bores. However when cold the extra clearance allows the pistons to pivot and touch the bores causing the piston slap.
The rate of expansion and the amount of expansion is dependent on the Alloy. Better quality pistons (read more expensive) can have less clearance as the alloy does not expand as much when heated.
As for Nitrous they say that you should have slightly more bore clearance due to the sudden increase in power i.e. 100hp or more in a split secound can cause extra expansion in the piston.
As an aside if you give the engine a boot full when cold some blow by can occur due to the extra clearance
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