I'm pretty certain my MY98 has a bad case of piston slap - this year is known to suffer quite badly and Subaru produced modified parts to rectify this. It sounds like a bag of nails when cold, but almost becomes silent when warmed up properly (15 mins+ driving). I haven't had it diagnosed properly but there's not really anything else it could be.

Now I've read a number of threads on ScoobyNet about people having piston slap and then having their big end bearings fail or the engine goes bang or whatever. Other people say they've had this slap for many years and it's never been a problem. So...

What is really going to happen to mine??? It gets driven very hard quite a lot of the time, although not until warmed up . I change the oil regularly (every 5-7k) with high quality, highly recommended stuff and there is never any metalic deposit on the magnetic sump plug and the oil doesn't seem to be in bad condition with no grittiness to it . Is there really any serious damage being done?

I look forward to your responses...

Cheers

Ben

 

i read somewhere the vibration piston slap causes means the big end/crank gets the brunt of the vibration thus the big ends going......but im no expert.

 

My 1998 wagon has had piston slap since new, mileage is now 180.000 km. It is frequently used on track days, no problems so far.

 

I had my engine fitted with built in piston slap, i've got forged pistons

 

Cheers guys.

So far it would seem that piston slap isn't really an issue. I'm suprised though that nobody has replied saying their engine has packed in due to it.

Are there any pro mechanics out there who could give their opinions?

Ben

 

A good look on search and you will find that the engine people say that as long as the slap goes when hot and not consuming too much oil then the engine is fine. Detailed seach might be better as you are able to specify the forums searched.

 

My 97 sounds a bit noisy during the first few minutes but is fine after that. Doesn't uses any oil, no problems to date.

 

IMHO piston slap shouldn't have an adverse effect on the big ends, yes it will transfer some vibration down the crank but the piston will be turning slightly at the little end as it is designed to do.. It doesn't do much for the cylinder walls and your rings though

 

How come out of interest?

Robin.

 

That's exactly what I would have thought Davey. I certainly wouldn't expect NO damage is being done. Mine doesn't use any oil whatsoever, so things shouldn't be too worn yet!

I think I'll start being concerned when it starts using oil.

Cheers

Ben

 

Ive have some slap and until it gives me some real problems then I'll leave it well alone. I understand your concern about spending a couple of K on a new engine but mine gets hammered (Dont read this if I ever advertise it on scoobynet) all the time after a good warm up.

When my MY98 WRX 2.0 goes bang, its 2.5 time!!

 

I opted for forged pistons on my 2.5, as they are known (by the tuning bods) to be more resilient at higher boost. They slap because of different expansion properties, but are fine once fully warmed up.

Andy