Piston Slap
 

Which cars did this affect?

I seem to remember it was the 1996 cars mainly?

Does it appear in the latter cars at all?

How does it manifest itself? I assume it appears when cold only and a Top End tap?

Pete

iv heard mainly 98 cars

Yes I heard '98 cars also, whether there is any deviation on this I am not sure.

Apparently it is due to the piston diameter being slightly too large for the bore, and as a result the piston ovalised upon usage causing piston slap as a design error. Although I stand to be corrected.

Robin.

Nowt to worry about though, is it??

Nothings going to break??

Pete

As long as it clears when warm and it's "your" car, no problem :)

Is 'my' car special then?? ;)

I am being asked questions ......

And it seems that the noise disappears after about 30 seconds of running and only appears under load - not there when idling, but after about 30 seconds not there at any time?

Pete

Agreed.

Why would 'my' car be different than anyone elses??

Pete

97/98 cars pete ;)

Tony:D

Sounds like nothing to worry about, if it is a 'tappety' noise it could be just the hydraulic lifters filling with oil. If it is piston slap, and it disappears when warm, then it is not a problem, just not perfect.

Robin.

Could be those dodgy oil changes you've been doing also Pete? ;):p

Tony:D

Apparently it's like tappets - but a deeper sound and under load only (tappets would tap at idle too).

Pete

Ha Ha Ha ... yes, I wonder if the owner listened to my procedure of Oil chnage rather than the Anals?? ;)

Pete

Use a thicker oil?

Tony:D

I have a variety of noises from my engine bay, I have eliminated my tappets, and I havn't any piston slap.

I know that I have a clicking noise from my boost solenoid (on drivers side suspension bulkhead in engine bay), and this is only apparent at about 1500 rpm and above, wether under load or not.

And I believe my cam belt tensioner/idlers to be worn (car is over 100,000 kms), and they seem to cause a sporadic ticking noise at times, on idle-not sure about under load.

Hope this helps

Its those 'value molecules' eating your propshaft Pete ;)

rob if your cam belt tensioners or idlers have ANY !! problems get em changed asap

pete yhpm re seat covers

96-to end of 98 (so may include early reg 99 cars )IIRC.

It is a highish, rapid "clinking" noise, sounding from the middle to upper end of the engine towards the cylinder heads in time with the engine rotation. That is very prominent when cold, and increases in intensity on acelaration or when you lightly rev the engine.

It was about the time Subaru started using their fancy ceramic and molybdenum coated pistons.

Due to differentiating thermal expansion properties of alloy pistons and steel cylinder liners. Pistons are sized accordingly to fit correctly when HOT to prevent scuffing, wear and at worse - seizure. So this can mean the pistons are excessively undersized when they are cold, thus allowing them to rattle around in the bores (piston slap).

Subaru got the calculations a bit wrong, where they considered it to be too excessive and potentially could cause problems at the latter stages in the engine's life. I personally think it was an overreaction from Subuaru addressing customer's whose engine's "funny noise" were causing them concern.

As long as it stops completely when warm (within 30mins absolute max...norm is 10mins). It should not really ever cause any problems. But eventually, due to the contact of the piston skirt with the bore, it will scuff off the protective coatings, and the bores will wear excessively oval (all piston bores on any engine eventually wear oval due to nature of a piston's movement), causing piston ring sealing problems and an increase in oil consumption, blow by gasses and reduction of cylinder compression. By this time piston slap would probably be very persitant. And maybe present until the engine is completly warm (well over 30mins) or still persitant when hot (although not always nessecerily the case).

So to sum up: Long term effect is the engine's overall life span is reduced. But your talking well over 100,000 miles, probably 200,000miles at a guess. Which I'm sure the big ends would have long gone before then ;):D:D

Next job on my list!

Since she had the kid, I've suffered from really bad piston slap !

Can you get an oversized replacement piston? :D

Just wait until the 2nd, it gets worse!

There was a sound file of piston slap on here a few years ago. I had the prob when I had a MY97 and the file proved it when I listened to it.

Sometimes piston slap isn't there immediatly you start up, but becomes apparent after 20 - 30 secs as expansion differential starts. Obviously this is not always the case but can be one scenario.
There were occasional problems with cam belt tensioners at cold start up, allowing it to "bounce" slightly against its stop. This sounded just like piston slap, and like slap, went away as the engine warmed. (I had this on my 99my - yours is a 2000my I believe?)
JohnD

It could be Det if it's appearing under load Pete... What's yer knocklink saying?

CockLink is all quiet, thanks .... I was told to adjust it until it never shows RED - it's really only there to impress the Chavs at MacDonalds :D

Thanks for all the posts .........

Pete

you havnt got your frocklink set proper you know thats yer problem that is!!!!

wouldn't worry about it tbh

mine had a rebuild after i did an anal oil change and the pistons were checked and said to be in good order so they were left alone

noisy before it was rebuilt and is noisy afterwards, tbh it does not bother me in the slightest

Sorry - you are joking aren't you? Have i missed the great PSLewis getting a knocklink? :lol1: