Piston Slap

Author
Discussion

nobbybombshell

Original Poster:

1,350 posts

246 months

Monday 22nd December 2003
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My boss has been told that his scooby is suffering with this, can someone please explain to me what it is.
Thank you.

gdr

586 posts

259 months

Monday 22nd December 2003
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'Tis completely knackered.

matt_t16

3,402 posts

248 months

Monday 22nd December 2003
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In short concise terms piston slap is the noise produced when the piston hits the cylinder wall. Normaly almost instantly as the cylinder fires at the top(ish) of its stroke.

Normal cause is the piston/rings is/are worn allowing movement when the piston is underpressure i.e it is no longer a correct fit in the bore. Under extreme circumstances it can be because the piston has been 'ovaled' or damaged due to excessive boost in a force inducted engine. Or it can simply be due to the normal wear and tear on a high mileage engine. Either way its likely to lead quite quickly to a dead engine. The only exception to this is an engine with forged pistons when started from cold. Due the thermal expansion properties of a forged piston over a cast one (i.e. they expand more) they have to machined smalled so when hot they expand to fit. Hence their will be a touch of slap from cold.

Hope this helps.
Matt

Justin s

3,637 posts

260 months

Monday 22nd December 2003
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apparently no 3 cylinder suffers worst on the flat four due to lack of lubrication on this one.

matt_t16

3,402 posts

248 months

Monday 22nd December 2003
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Justin s said:
apparently no 3 cylinder suffers worst on the flat four due to lack of lubrication on this one.


It does but thats more big end wear on no 3 than piston/ring wear although your quite right a lack of lubrication doesn't exactly help.

Matt

nobbybombshell

Original Poster:

1,350 posts

246 months

Tuesday 23rd December 2003
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Thanks for the info guys.

Mr2Mike

20,143 posts

254 months

Tuesday 23rd December 2003
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Piston Slap is a close relation to Piston Broke, a state I am in quite frequently