Piston Slap

[Vincent Reppucci]

Sorry if this is a repeat but I would like to get some feedback about
piston slap and engine longevity.

2002 2.5 outback 41K miles. This year I have noticed a ping/knock noise,
fairly certain it is piston slap, sounds like piston #4, very pronounced on
cold mornings, at 55 F or less. The slap is most pronounced under load,
even minimal, at about 1500 to 2250 rpm.

It seems to last, depending on how cold it is, about 10-15 minutes, I am
guessing until engine oil (and block,piston, etc) heats up.

So bad in cold that I do not wish to accelerate; something about metallic
sounds that make me leary, until it goes away.

Doesn't burn oil although gas mileage plummets; not sure if cold or knock
sensor being stimulated by the slap.

Dealer says knock, ping goes away, normal piston slap.

I am oncerned, seems to be worsening and is very annoying.

If this more than an annoyance I feel I should pursue this with SOA (can I
go over dealer's head??) any comments would be appreciated.

I live in Western CT

Thanks

Vincent

 

[Voja Ilic]

Vincent,

I had the same problem with mine OBSW 2002 at around 30K km (20K miles).
After leaving my car overnight in their shop (Vancouver, BC, Canada)
they took it for a test ride, heard the engine knock (or piston slap as
they call it) and decided to replace short block. It was covered by the
warranty.

It was fine for about 15K km, and now I'm hearing it again. So, I've
decided to try an engine block heater and see how it works since they
said there is nothing else they can do now.

Noise is much less noticeable (after heating the engine for about 2 to 3
hours before I go anywhere). It's still there, I can't hide it, but it
is better then before.

Voja

 

[Spudster]

Vincent,

I had the same problem with mine OBSW 2002 at around 30K km (20K miles).
After leaving my car overnight in their shop (Vancouver, BC, Canada)
they took it for a test ride, heard the engine knock (or piston slap as
they call it) and decided to replace short block. It was covered by the
warranty.

Voja, can you tell me which dealer you went to in Vancouver. Im going to
take my 02 OBS in for the same problem soon, and would like to know which
dealer is good enough to replace short block.

Thanks.

Spud (Abbotsford, BC)

 

[FFF]

Sorry if this is a repeat but I would like to get some feedback about
piston slap and engine longevity.

Not sure if that info is relevant to the newer engine, but someone solved that
problem on the 1997 2.5 DOHC by fitting Impreza Sport pistons:

<http://www.carsurvey.org/review_43338.html>

florian

 

[JustDoIt]

1997 2.5 Legacy, about 94K miles.
Pistonslap when cold. Don't worry.
Irritating but no harm done.
Like it or leave it.

 

[Michael R Kirschner]

I also have the dreaded slap on my 02 outback I have 36 k miles . The
slap srarted around 6 k miles . I have tried to have SOA take care of
it ,but they say as long as the noise goes away when the engine reachs
normal operating temp they do nothing about it . I had my oil analyzed
on my last oil change and the reading came back normal with minimal
wear . So I just learn to live with it ,and take it easy untill the
engine warms up .

Mike k

 

[Voja]

It was Don Docksteader Subaru while they were in Coquitlam, BC. They
closed it in March this year.

You can go now to Don Docksteader on Cambie, Vancouver.
Their web site is http://www.dondocksteader.com

Voja

 

[Roy Shroyer]

My 02 OBW exhibited the same symptoms. Remedy? Timing chain tensioner, not
shortblock.

Hope this helps,

Roy

 

[Crash]

that's what i thought, had the belt tensioner replaced, but had the same
problem back 2 days later.

 

[ct]

Sorry if this is a repeat but I would like to get some feedback about

piston slap and engine longevity.

'98 OBW, 2.5l, 118k. Definite slap in the morning when it's cold out
(around freezing). I think the car has been doing it since about '75-80k,
maybe the second winter I owned it (bought it with 65k).

It seems to last, depending on how cold it is, about 10-15 minutes, I am
guessing until engine oil (and block,piston, etc) heats up.

Same here.

So bad in cold that I do not wish to accelerate; something about metallic
sounds that make me leary, until it goes away.

I think even when it's not making any noise it's best not to accelerate very
hard when the engine is cold...I always wait until it's up to temperature.
I want to get a oil temp gauge at some point.

C

 

[DH]

Are you sure this isn't the valve lifters? Many cars suffer lifter noise on
cold startup.

And how the heck did you determine that it is the #4 cylinder?

 

[Michael R Kirschner]

I just had the timing belt tensioner changed due because of the cold
starting noise it was making . In my case it sounded very different
then my piston slap issue. Piston slap sounds like a sombody is
hitting the block with a hammer. My tensioner noise was a very deep
hollow knocking sound almost like the blowoff valve makes on a cold
diesel engine makes when you step on the pedal. I could also feel the
belt hitting the timing belt cover on the front of the engine ..

mike k

 

[Ronald Donahue]

Vincent,

90,000 miles on my 1999 SUS I have had what every one refers to as "piston
slap" on cold mornings since the car was new. The car runs fine no abnormal
oil usage and by the way I change my oil only every 15,000 miles.

Ron Donahue

 

[Vincent Reppucci]

Not the lifters because noise is not heard at idle. The knock, it is fairly
deep, is heard only under load; acceleration dependent and gets worse when
going up hills etc. Almost sounds like a bad rod bearing except bearings
get worse as revs increase.

#4 cylinder determination, unplug the spark plug and the noise goes away
when that cylinder is no longer under load.

The slap is also most prominently heard in the car and difficult to hear
outside the vehicle, unlike noisy lifters. Don't know why.


Vincent

 

[Voja]

Just came from my service shop. I've complained again re. engine knock
on cold morning starts.

Here is the official wording on their working sheet: (it was on 12/23/2003)

Tested on A.M. for line C-AT this time heard timing belt tensioner noise
with customer.
Cause: ADW-34
B241-201 Re& Re outer timing covers to replace
Noisy timing belt tensioner.


They've replaced it under warranty and this morning (12/24/2003) when I
started my car engine it was quiet. So far I'm happy

At least I know what the cause is and it can be fixed even if I have to
pay for it in the future.

Merry Christmas,
Voja

 

[Vincent Reppucci]

Voja,

Merry Christmas to you.

Please clarify the events here. They replaced the short block and the knock
persisted?? or returned??
and now they fixed the tensioner, which made the knock go away. Can you
describe the noise?

Could you have been blessed with two problems??


Vincent

 

[Vincent Reppucci]

never mind Voja read your other post. I also have trouble with Rt front
bearing and burnng smell at idle. I did see the wet axle; the dealer said
it was spill from when they changed the diff oil aout 5K earlier. I didn't
believe them. I will recomplain.

Thanks for your posts

Vincent

PS.I don't think I have the clunk on reverse!

BTW my gas mileage is about 24 mpg on highway. What do you get?? I would
like for it to be higher. I have tire pressures at 42psi and I do feather
the gas pedal. I think the piston slap might be setting off the knock
sensor.

Merry christmas,

Vincent

 

[Michael R Kirschner]

I was also blessed with both noises on my 02 outback . I was finally
able to have the tensioner noise taken care of . It took me three
times leaving it at the dealers overnite but they were finally able to
here it . Now all I hear for the 1st 5-10 mins of my car running is
the knock knock of piston slap.

mike k

 

[Edward Hayes]

Piston slap is the piston slapping against the cylinder wall. Pistons are
cam ground; that is they are not true circular but oblong when cold (looking
down on the piston top). Warm pistons become round due to expansion. If
there is a couple (~0.001-2 thousands extra clearance between cylinder and
piston then you hear the noise, especially when cold. My 2000 Forester will
do it for about 15-20 seconds after starting. I know what piston slap is as
my 1956 Porsche with aluminum pistons and alumni cylinders and NO water
jacket (air cooled) would wake the neighbors for about 1/2 minute and this
was normal. Some slap for the first several minutes or so is not cause for
alarm. eddie

 

[No Way]

Voja,

What the hell is piston slap?