I think I may be getting a little piston slap?

The car is a MY95 WRX with the usual breathing mods, running Optimax.

When the engine is under load, I can hear a very slight noise that sounds a bit like a helicopter..... is this piston slap?

If it is (which I REALLY hope it isnt):
What is going to go wrong with the car?
What can I do to stop it?
What causes it?
Why is my scooby such a money pit? (not through faults I might add
Why does my backache.....? etc

Any help would be greatfuly received, if anyone is local to Hemel and knows what slap sounds like, could you drop me a line and come and have a listen?

Cheers people

Paul

 

Know what you mean about sounding like a chopper mine did only when cold tho', load didn't seem to make any difference.
Don't know that slap does much harm but I have seen something about the piston skirt breaking on another thread. Compression will be somewhat down cos the piston doesn't fit the hole anymore. TSL rebuild my engine now damn good, shame about the overdraft, their guys could tell what the problem is I've know doubt but that Nottingham.

 

I've just read wot I rit an' it's v bad!!

 

Danny, how much did this cost you?

 

Have a listen to this recording of what piston slap sounds like, recorded by AJ Leslie from our bbs. When you click it, a rego form comes up, just click later. You don't have to register. Then you will hear it.

http://homepage.ntlworld.com/alan.leslie/

Cheers,

Wrexy.

[Edited by WREXY - 10/23/2001 2:28:51 PM]

 

Mine does not sound like that......

Do you think I will be ok then?

Cheers

P

 

Mine sounds like that when cold

Once it's warmed up it sounds & goes fine.
This is my first Subaru and I presumed they all made that noise (along with the noise they make when you turn the engine off).
With it being an MY97 I thought piston slap only seemed to occur from 98 onwards so I wasn't concerned when I brought it (private sale).

Am I doomed to a life of eternal expense then or will it be ok?

Matt

 

i was speaking to subaru's technical dept. about the piston slap on mine this afternoon,they have told me that the problem is only with the 97 facelift models onwards(which mine is).

the other reason they gave me if it isnt piston slap but sounds just the same,which could be whats wrong with yours is the timing belt is stretched or the tensioner needs adjusting.better than piston slap?!

let me know the outcome,
steve

[Edited by stevie c - 10/23/2001 4:56:48 PM]

 

Neanderthal,

You're not doomed IMHO. My car's had piston slap for a good 15000 miles now (currently on about 56k). There have been no visible ill effects (cue somebody telling me about the hidden ones...) and my oil level never seems to drop between services. I've heard scare stories, but I'll believe them when my engine blows up or if anyone has conclusive proof this can happen due to slap. The worst I've heard is that the engine life may be about 90% of normal and the inevitable rebuild (that all engines eventually need) may come a little bit sooner eg. at 135k instead of 150k (or whatever). Anybody think I'm seriously wrong?


[Edited by scoobysnacks - 10/23/2001 5:00:35 PM]

 

I'll be interested to hear the outcome Steve.

Scoobysnacks, you've helped put my mind at ease. Mine has just gone over 50k miles. I'll see what they say at the 52k service.

Matt

 

Oh - mine's just started to sound a bit like that, hot and cold but only at about 2500-4000 revs. I just thought it was a loose heat sheild or some such. The noise started after trying a couple of rapid starts to reduce clutch judder.

What causes piston slap?

 

piston slap is a round cylinder sitting in an oval hole,so obviously its not a very good fit!
but as the engine gets warm,metal being metal starts to expand,filling the gaps!but before it expands it rattles about,sounding like a diesel!
i think this is right anyway!
steve

 

OK - so what causes the hole to go oval in the first place? Is it: bad manufacture, owner abuse, some combination of the two or something completely different?

 

I agree with Scoobysnacks. My MY98 started to make the dreaded diesel sound at 68000 miles, and has been doing it ever since at cold up to its present 92000 miles, with hardly any change. It's worse in winter (obviously) and nearly goes away altogether after hot summer nights. I think its too late to change a single piston now, and I'll just wait for the whole thing to go bang. It pulls a consistent 20psi, so its hardly understressed!

BTW, Dannyn, the piston itself doesn't do much for the compression - its only there to hold the piston rings in place, they do the real job. If you've seen the depth of skirt on a racing piston, a bit of slap on a production piston isn't going to affect the compression at all, imho.

Graham

 

I don't think piston slap is anything to worry about. Sure if you have warranty get it done. But if you haven't leave it.

Some old US performance cars, the big V8 special edition cars came standard with piston slap. It said it in their owners manuals. All of the people in OZ including myself who had built some big V8 engines with forged pistons had piston slap from the first kick over and these had piston slap hot or cold as the forgies do not expand. We were assured by the engine builders that it was nothing to worry about. Unless the Scooby engine is different ie weaker materials, there should be no worries IMHO.

Cheers,

Wrexy.