Hi there,

I appear to have a serious engine problem with my uk turbo 2000 (my99/00) which I have been told is piston slap. The engine knocks from piston 4 from cold, but is quiet when warm. The car has only done 55k and has full subaru history, so am really unhappy with this situation.

Anyway have been told that the only solution is a recon engine (£1800 + vat + fitting from API), is this the case or can I get away with a new piston or new short engine?

Cheers

 

Quite common to have piston slap. If it clears up when warm, then dont worry about it. Only go to the expense of an engine rebuild/replacement if it starts burning lots of oil.

Feel sorry for the guys with forge pistons when cold sounds like a bag of spanners.

Andy

 

It use to be a complete new short engines on the 97/98 cars which this fault was common with, you dont see many 99/00 cars with it.
The end solution was just to replace the piston with an oversized one I think.

Tony

 

Lots and lots of 97/98's have the problem. It was a warranty replacement short engine - IF you could get Subaru to agree to it being a problem. Of course, the fact that it goes away after 5 mins did mean that some dealers wouldn't agree to it. Which is why you find lots of FSH cars that still have the problem.

Anyway, if it goes away when the engine warms up, then I really wouldn't worry about it. Don't spend that sort of money unless you have too. You can go for tens of thousands of miles without it being a problem. Just take it easy until it warms up - which you would anyway - You yust have the advantage of an audio messge to let you now when you are good to go

 

If it goes away within 5-10mins, has good compression and doesn't burn oil, then don't worry.

You can fill the sump with a thicker oil which can quieten it down. Just be aware it doesn't "fix" or prevent it. it just deadens the noise.

If you've ever seen the shallow skirt design of the pistons on these engines, it is very understandable why they do slap. especially combined with the light alloy metaluargy and steel bore liners which have differing rates of thermal expansion and contraction. If it was the other way round and too tight rather than loose, the pistons would seize and scuff the bores.


You know Dave Api's number. Ask him. And you'll save yourself the cost of an engine.

 

Had this issue on my old sti 4. In the 2years/15000miles that I drove the car, it didn't burn any oil. The noise seemed worse on cold moring for obvious reasons, but would always dissappear after 2miles/3-5mins.
I have the same noise on my MY99 UK turbo. Again, it doesn't burn any oil.
I wouldn't worry about it mate, it is a very common fault, but is isn't terminal. Its just a 'characteristic' of the boxer four!

 

I too have just started to notice this on mine.
Glad it's nothing to worry about, YET!

 

i "think" i am getting this noise on mine

an uneven knocking when cold that goes away very shortly (2-3 mins) when warmed up.

Is it actually causing any/much damage?

 

Someone should start a sound clip archive or the various sounds an Impreza engine can make to help us ID our problems.

I think STI V2 piston slaps when cold, but as normal; only for a minute or two.

 

Mine does it on a very cold day for a few mins. Will try to record it when the weather gets a bit colder and when I leave it outside (it lives in a heated garage overnight, so generally doesn't always do it - Or you could just listen to a Rover K-series when cold, they all do it. As do the post post MY2000 Clio 1.2 engines, amongst many others).



This is the 2nd engine as well...the original bottom end was replaced for...guess what?...... piston slap!

Admittedly, it was quite bad, clearly heard in the cab and wouldn't shut up for at least 20mins and even longer on a cold day. (and it was an independantly owned Subaru dealer, so maybe they were "looking" for extra work )

The slapping noise ocurrs when the froces on the piston skirt changes sides in the bore just before and after BDC and TDC (bottom dead centre, top dead centre ). The clearance is what causes the noise. The force and friction on the skirt and bore is still there with or without piston slap. And there is anti friction coating on the skirt to prevent wear, as well as residual oil film.

However, slap can be caused due to piston and bore wear. So if an engine does it for a prolonged period or when hot, it is likely to have excess wear and will possibly consume oil and have lower compression as well.

Anyway, if in doubt ask Dave@api. I trust him more than I trust my Isuzu Trooper.

 

i think im getting something similar but its doing it all the time, warm or cold. started suddenly 3 days ago. was cooling her down, hadnt thashed her or anything, and heard what sounded like a diesel engine noise, tapping sound coming from the engine. went to inspect, and thought all sorts of bad things...
started a thread in here and general and it seems my life is over. gonna see jason at scoobybits asap and see if its worth even keeping the car or selling her as spares. **** knows, but im not happy with the ***** who sold me it 6 months ago. live and learn i guess.

hope you guys sort your problems out, me too i guess

andy

 

My car is a bigger slapper than my mates wife.. but has forged pistons.
The noise is still audible when hot, and the engine was only rebuilt 25,000 miles ago..is this "donking" noise quite normal for forged pistons?

 

My 2.5L is a bit of a slapper (oh yeh ) when cold...but only for about 2-4 mins, after that, det cans only show noise from drive train of heads (as lary cams)...First time I started her from cold, thought there was something wrong but then clicked, forged bits make noise (my motors now done approx 1500miles since built). Nowt worry about, unless using lots of oil.

 

Piston slap is only a noise after all said and done, I do not recall a conversation aboout a full rebuild specifically to cure piston slap.

My advice always is: leave it till it doesn't quieten when warm or when it uses as much oil as fuel.

It is not doing any harm until it does either of the former. Save your money until you need to spend it.

David APi

 

mine has knocked for the past 3 years


wouldnt worry about it TBH

 

words of wisdom - thanks David

 

If an engine starts to make the noise when warm rather than when cold what does that signify? Worn bores? If it is using no oil I take it that it would not be piston slap but maybe worn little ends?

 

Worn little ends is not common and certainly not all four in one engine.

If it's an early car it's more likely to be loose hydraulic lifters. After 1997 when they have solid lifters then it may well be piston slap which will be quite a bad case if it stays the same when warm.

The advice remains the same though, Until it uses lots of oil it's just a noise.

Unless you think you may have forged pistons fitted which clatter all the time hot or cold.

David APi

 

i wish my engine was just piston slap but its definaltley dying a sad sad death on me. im going for a beer or 10. apologies for the rant...

andy

 

I have a MY 99 wagon and at first I thought I had tappet noise so ran an engine flush and changed to fully synthetic oil but it remained the same. The tapping/knocking is noticeable when hot or cold or if the engine is under load at low revs ie hill starts. However it does not seem 'deep' enough in sound to be main ends but more like little ends or piston slap. I am not losing any oil so I guess will just see how it goes.