David_Harden

My MY95 WRX has had piston slap for a year or so. I have 80k on the clock.

By unplugging the HT coil from each cylinder in turn I have determined that the one which is slapping is the back one on the passenger side (piston number?). The knocking noise goes away after 5 or so minutes.

I've done a brief search on scoobynet and it seems that since I don't have any warranty to get it fixed, it isn't worth sorting out. Is this correct?

What I don't want is to have a much bigger repair bill later cos I ignored it now.

For info, I never push the car above 2500rpm until the engine is warm.

Comments please.

Thanks

David

JIM THEO

I don't think there is a problem if you leave it as is, the same cost if you replace it now or later.
In worse case you'll have the slapping noise all the time which means you have to change it the soonest possible.
JIM

JohnD

iTrader: (5)

Although you don't exceed 2500rpm also make sure you keep the engine lightly loaded during this period.
It would be good if we could pull back the ignition advance during warm-up to kill the slap!
JohnD

David_Harden

Thanks. Yes, I forgot to add, I don't put my foot down either.

I'm surprised you say that altering the advance would cure the problem. I can't see why, although that could be explained by my lack of knowledge!!

Thanks guys.

David

JohnD

iTrader: (5)

Piston slap has been (and still is) a problem to manufacturers and is not just a wear thing. There have been a number of ways to reduce slap employed by engine makers over the years and restricting ignition advance while the engine is cold is one. I remember this being used by Ford on the 1.8 CVH engine used in the Sierra Sapphire following comments regarding noisy engines when cold. I had a Nissan Sunny 1.5 back in the '80's which had very noisy slap right from new and I remember pulling off the vacuum advance pipe from the distributer as an experiment to limit advance - and it worked! Killed the performance of course, but it proved a point. Other methods are offsetting the gudgeon pin from centre in the piston, ovality in the piston when machined etc.
With the ultra short, solid skirt pistons (no expansion slits) used today, slap can be a problem. In the early Sierra Cosworth handbook it stated that a certain amount of piston noise may be heard and should be ignored!
JohnD

bigunit

I have same problem on my98 uk turbo 52000 full service history (every 6000 max) slap bad when cold but i can still hear it when hot but not as bad same piston as mentioned above can only hear it inside car passanger side and under light load, from outside cant hear it only when stone cold.
It bugs the hell out of me getting service in 2 weeks going to put 10w40 motul in has had semi synth in all its life. I have only had car 3 months and besides this problem i love the car and is in mint condition. Thinking about saving for engine rebuild and upgrade to around 350 bhp but should i sell it and get a type r or what ? hmmm
How much would it cost just to have pistons replaced any ideas parts and labour?

StickyMicky

mine is noisey in these cold mornings

fine when warmed up tho, to be honest its now got about 86000 miles on it and i dont see the point in fixing it when its bound to blow up at about 120 000 miles or so, so i have just left it alone

it doesnt really bother me that much