Can someone explain to me what this is as someone has said my Saph is suffering with it. What is it, what damage can it cause, and how can I fix it?

 

when the cylinder bore wears on its thrust side it allows the piston to `slap` against the inside of the bore.

 

oh yeah, to answer your other questions: it can cause excess smoking and i assume accelarated bore wear.can only really be fixed by either reboring and using suited pistons or by buying a new block and new standard sized pistons. hope this helps!

 

Hi there,
Simply put, piston slap occurs when the piston is forced against the side of the cylinder wall due to piston to bore clearances. It follows then the more clearance there is the louder the knock will be.
Piston slap usually occurs when the engine is first started from cold. The piston, being made from aluminium has a different thermal expansion rate than the cylinder bore which is cast iron. As the engine warms up the piston expands at a greater amount than the cylinder bore, thus reducing clearance between piston and bore. As the engine warms up this noise should go away!

Hope this helps

CheeRS, Mike.

 

Hi again,
You want make sure that this is piston slap, as get it wrong and it could be costly if you end up rebuilding the bottom end and it just turned out to be a lifter or something minor!
Does the car make this noise all the time or just when started from cold?

CheeRS, Mike.

 

mine does this when warm, quiet from cold??

 

Mike

What is confusing is, it doesn't do it at all. My mate looks after my car and we've had loads of comments from people that its the quietest engine they've heard, it runs fine and there is no slapping that I can hear.

I think the garage where I had my crank sensor done are trying to pull a fast one. I'm driving up North in a few weeks (600 mile round trip) so I'll see what happens with it then.

Thanks for the replies, at least I know what it is now

Matt

 

You need to go back to that garage and slap that mechanic with a piston, I hate it when they try to take advantage of unsuspecting customers.

 

Does the engine need a rebuild when piston slap occours with warm engine?

 

just a quick one has anyone suggested to check your oil and do u have a good quality oil in there as mine sounded tappy with too thin oil in it i put 10 w 60 millers in it and its quiet as a mouse mine ended up being a slightly noisy cam follower