airhead

just need to know some facts about piston slap.

What is it.
What causes it.
How to ID the problem exists.
How to fix it.

No problems, just curious

WREXY

To identify it, listen to this recording of it.

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

I'm no expert, but here is a very simple explanation of it.

It is when the piston is too small for the bore and the piston slaps around in the bore. Usually when cold. It dissapears when the engine gets hot coz the piston expands, filling up the bore.

Causes are wear and tear or in the MY97/98 case, a factory problem with some cars.

The fix is, replace the piston with an oversize one.

Cheers,

Wrexy.

M4

NO! DEFINITELY NOT!

Either replace the duff piston with one of the same size (if the pistion is worn) OR rebore the cylinders and use an oversize piston (oversize in relation to the original).

You can't just use an oversize piston in a worn bore!

M4

WREXY

That's what I always thought and is the right way, but, the dealers are just fitting an oversize piston under warranty fix.

Wrexy.

scoobyboy

m4 the bores will not be worn at all so no need for a rebore and the oversize piston is only 60 microns bigger so it will not affect the engine at all. i've done loads of these fixes and never had a problem with any of them.

Steve Terzo

I think i have piston slap on my terzo (my98), it's now out of warrenty. I asked my dealer about it and he told me not to worry about it! My concern is, if i leave it what is likely to happen to the engine long term?

airhead

yes, very good question.....

CHRIS_D

im with you on that steve
same symptons on my MY98
im after the same answer, anyone??
chris

WREXY

I'm no expert andI might get some answers here from someone more technical than me with my answer to this, so here goes.

IMHO I don't think there will be any long term damage because I used to own a Ford V8 in OZ with a heavily modified engine and it ran forged pistons. These forgies have a fair amount of piston slap because the bores are honed to have larger than normal clearances and lots of people I know including myself never had any long term problems.

I also had a performance book on Fords which said that the old US Ford performance cars built from factory, I think it was the cobra, had forged pistons and in the owners manual it said that some oil consumption and piston slap would be normal due to the forgies and that it did not mean that the engine was faulty.

Cheers,

Wrexy.

Steve Terzo

Wrexy, thanks for your input on this thread, as a few years ago I owned a renault 19 16v, which also had piston slap.
As far as i know, this was a "characteristic" of the earlier engines-to the point that heavy oil consumption was widely accepted for that model!
Which makes me wonder, apart from the "diesel" noise on start up...Is it such a big deal after all?
Any more comments would be appreciated!

dela

I have my STi v3 serviced at Park Lane in Alton.

They confirmed it has piston slap when cold, but told me not to worry about it as it goes away when hot.

I'm now extra easy with the revs (sub 2.5k) when driving the car cold, and it seems to be fine when warm.

Basically, I've stopped worrying about it.........

Dave

WUZ

iTrader: (14)

The only problem with piston slap is at selling time..............some previous threads (confirmed by visits to dealers about buying a new STI7) show that dealers are aware of the problem and will reduce the trade-in value of a Scooby with piston slap by £900-£1000 . Bit of a bitch when it can be fixed with an overbore piston for less money!
Apparently no serious long-term damage (info supplied by the "they all do that sir!" posse - I don't believe a word of it!) but mine has been doing it on cold for 2-3 months (sound gone when warm!) and it has annoyed me for long enough so it is being done. Better off in the long run, honest

Russell

Greenfin

When I had pistonslap on my MY98 the number 4 cylinder was badly worn! It was oval.
What they did was that they rebored all the cylinders and put bigger pistons in every cylinder.

This was 9 months ago....the car is working fine

ga33a

Hi All,

I developed piston slap on my MY97 at about 50,000 miles. Took it back to the dealer who contacted IM and they authorized the repairs at no cost to myself.

As for "it's not a problem" ignore that advise and get it fixed!! It's a KNOWN problem with the car so hopefully you shouldn't get too much hassle.

Cheers

Gazza

stevie c

I was in the same boat as gazza,slap at 60k.

Paid for on extended warranty by IM,sounds alot better now.

steve

WREXY

I agree, if you have warranty by all means get it fixed. Why leave it, if it gets done for free.

The question is should you fix it if you have no warranty?

Cheers,

Wrexy.