Do you know of a way to fix it that doesn't require a complete engine tear down ?

Most Subaru 4 cyls I've ever heard have it to some extent. Mine has since I bought it 85k ago, wasn't too bad when I got it and hasn't gotten any worse.

 

My wife's 2002 Outback 2.5L has had it since 40,000 miles when she bought it used. It now has 151,000 miles. It's gotten a little worse but once the motor get up to operating temperature, the knocking noise is almost gone. I don't think you can really be 100% sure to get rid of it without a tear down and new liners or bored out and new pistons put in. Just replacing the piston is most likely just a shot in the dark because the clearances on the piston to be right are only a couple of thousands of an inch. I plan on putting in a short block one of these days.

 

My 3.0R slaps some as well when it's cold. I don't hear it from inside the car these days but if I open the hood I'll still hear it until it warms up.

Every other Subaru I've had has done the same thing: 95 Outback, 02 Legacy, 03 Forester.

So long as the noise goes away after 5-20 minutes of the engine running you're fine. If it gets worse as the engine warms up I'd start looking into not-so-nice possibilities.

 

My 3.0R slaps some as well when it's cold. I don't hear it from inside the car these days but if I open the hood I'll still hear it until it warms up.

Weird...my 3.0R is butter smooth as soon as I start it even on the coldest days. Same with my old '04 with the EZ30D. I always thought the H6 was basically immune to this...

 

Well, interesting so far.

Thing is, I have to have the engine torn down for head gasket replacement, and I asked them about fixing the slap at that time. Not a whole lot more to do it, but it is more money.

I certainly wouldn't have the thing ripped apart for only piston slap.

What the tech told me is they replace the RH pistons with special ones that have maybe 2mm more skirt.

Basically, I'm trying to find people who have had these installed, and if they made the noise go away, and stay away. I figure to keep this car 200,000 miles, and if I can do without the noise, that's one thing, but it the noise comes back after, say, another year, that's something else to consider.

 

I'm running a related thread, and tying them together.

http://www.subaruoutback.org/forums...rg/forums/66-problems-maintenance/133457-definitive-piston-slap-question-3.html

 

Keep in mind that the term piston slap is a description to describe the sound that the Subaru engines make when cold. Its not a mechanical issue that needs repair its a description of the sound these engines make due to how they are designed and sound when cold.

Trying to repair this would mean putting a Honda engine in a Subaru given the Subaru engines by design get the piston slap sound when they first start up and run cold. Only way to repair it would be to put a different type of engine in the car.

Let us know how the honda engine conversion goes then you might have found a fix for "Piston Slap"

 

So I realize this thread hasn't been visited very recently, but subiesailor, I'm going to have to fundamentally disagree with you. Yes, piston slap is often described as the initial sound these EJ engines make when cold. Yes, it's likely not a mechanical issue that needs repair, just an annoying sound. And yes, it's normal for these engines to sound this way when cold.

But actual "piston slap" is the sound caused by too much clearance between the piston and cylinder bore. The "slap" sound is caused by side-to-side motion of the piston as it travels through the cylinder bore, rattling against the bore itself (perpendicular to the normal travel of the piston) rather than it's intended parallel motion to the cylinder bore. These engines normally sound this way when cold because as the engine warms the pistons expand slightly due to heat, and lessen the clearance between the piston and the cylinder bore, thus removing or lessening the "piston slap" noise.

It's pretentious to say "Let us know how the honda engine conversion goes then you might have found a fix for 'Piston Slap.' " 2+2GT was just gathering information to make an informed decision. No need for sass there.

 

Hmmm… That's an odd way to look at it. There was no such noise for the first 65,000 miles. I suppose it might have had a Honda engine, then at the 65,000 mile point the dealer slipped in a Subaru engine. But I doubt it.

Hasn't anyone here ever had this fixed? Someone certainly has, Subaru has made special pistons for the job.

 

The point is there is nothing to fix other than to sell the car and go buy a different make with a different engine design. Sorta like purchasing a pink pair of running shoes then asking people if they have gone through the trouble of trying to dye their pink shoes a different color.

 

Don't get us wrong. We're not saying don't attempt it. It's entirely up to you.

I suppose if somebody told me, for example only, that since I have my engine torn apart for head gaskets it's another $500 to reskirt the pistons and there'd be no more slap sound I'd likely say yes to the job.

That said, $500 is an example. I don't have any idea what the cost would be. Could be $200, could be $2000.

All we're suggesting is that there has been no harmful occurrence has happened upon your engine to cause this and no harm will come to the engine because of it. If the slap-sound-annoyance/money-to-fix ratio has been exceeded in your opinion then have it fixed while the engine is out and taken apart.

 

I didn't bother having the oversized pistons installed in my Outback a 2 years ago when I had the head gaskets changed. It would have cost me another $1000 with parts & labor (oversized pistons w/ rings in #1 & #3, new rings on #2 & #4) and probably some other smaller parts & gaskets.

I have about 140k miles on it now, running 5w30 Castrol Syntec and it still doesn't use any oil. Piston slap is still there when cold though.

 

It's just some of the older EJ25s that have the more evident piston slap....like my 03 Outback...
Both my 06 Forester & 05 Impreza have newer version EJ25s and they don't make any evident slapping noise..

 

Interesting. The cost I was quoted was a lot less than $1000. They tell me they replace the pistons on the right side only.

What I'm looking for, I guess, is someone who had it done and drove the car a long time afterward. If the sound stayed gone, I'd be OK with the cost. If it would come back in a year or two, it'd be pointless.

 

What year/model car is it ?

Is the sound constant ? Pronounced ( like hear it in the cabin) ?

Mine you have to have the hood open or it has to be quiet then you can hear it a bit standing outside.

What type weight oil do you use ? Have you tried other brand/ weight oil ?

 

Classic symptoms, chatters when started cold, especially in cold weather. Five miles later, not doing it.

As for it being a design problem, sure. Except, of course, that there was no trace of such a sound for the first 65,000 miles.

I'm still waiting to hear from someone who has had it fixed.

I'm not interested in hearing "there's nothing you can do but sell the car". That's not gonna happen.

I want to know if the repair works. That is, does it return to the characteristics it had before 65,000 miles, i.e., no piston slap at all? Or does the piston slap come back after, say, a year?

 

Why is it that you think this "Piston slap needs to be repaired?" No its a very serious question.. My experience with auto shops and having worked in one is that if a customer has a very odd ahem burr up their back side and insists on fixing something that really has no issue or needs to be fixed - the shop will offer to do some sort of repair to make the customer feel as if they addressed their own concerns even if they were totally unfounded and more or less self generated.

Let me ask you this question can you go out today and pay cash for a new car? YES OR NO? -- If you like most people cannot just go and drop 30K cash on a new car - then I'd say that your concern and insisting on fixing Piston slap on your existing car is beyond silly and you should be saving your money. And thats coming from someone who paid cash for every vehicle ie all three parked in the driveway for which I nearly own outright.

 

Just so everyone is on the same page, here is a video description of the problem: Subaru Piston Slap : Seattle Area Subaru Repair and Service

The solution to minimizing piston slap is to install pistons with a longer skirt. The drawback is increased fuel consumption since the reciprocating mass is increased quite a bit.

 

subiesailor-

I appreciate you taking the time to post, but I think you have missed the point of my question. The engine will be removed and disassembled soon. This is baked in. No way to avoid it. I'm trying to evaluate whether the slight additional cost of having the RH pistons replaced will be effective. Not cost effective, just effective, as in does the sound go away, and does it stay fixed. You haven't answered that. Have you had this fix done?

phatvw-

The solution to minimizing piston slap is to install pistons with a longer skirt. The drawback is increased fuel consumption since the reciprocating mass is increased quite a bit.

Now that's a conflict with what the tech, who actually does the work, told me. They replace only the RH pistons, and that could not be done if the longer pistons (about 2mm, he describes) if they did not remove a slight bit of material elsewhere on the piston to equalize them with the LH pistons.

 

^^ Apparently the fix does work with the 2 passenger side pistons being replaced with oversized, but also make sure to replace the rings on both the drivers side pistons according to the Scooby specialist who worked on mine....I can't vouch for longetivity though since I didn't have it done...but I guess it also depends on how good of a job is done...

 

Interesting. I would not have considered having the other side re-ringed, since the engine consumes no oil at all (actually a little weird). The tech specified only the RH pistons would be serviced, and I find myself wondering why the LH side, which apparently is working perfectly, would need service. Something to consider.

didn't fix it, don't regret it.!!

Yeah, I'm getting a lot of that, but I'm on an entirely different track here. I want to know if the piston slap fix works, not if it's necessary. Oddly, no one here seems to have had it done. So I still have no information to decide.

 

didn't fix it!
don't regret it!

97 obw ltd with 98k miles.
it was advertised as needing a wrist pin, a connecting rod issue.
i bought it expecting to swap in an ej22 i already had.
the more i drove it and learns about piston slap,
the more i drove it and didn't care.
i drove it 40k miles .

i sold it to a friend for slightly more than i paid,
and i promised to buy it back (less 10 cents a mile)
if the engine failed due to the ''engine noise''.
(not if it ran out of oil )
she drove it for two years and was then sideswiped.
the insurance company bought it from her for almost $1000 more than she paid.
good for her.

didn't fix it, don't regret it.!!

 

Oddly, no one here seems to have had it done.

that should tell you something.

what is your criteria?

 

I'm basically trying to find out-

1) Does the fix work? [apparently it does]

2) Does it stay fixed, i.e., does the piston slap come back in a month, year, whatever? [I'm getting nothing on that]

Since the engine will be torn down regardless, going a little farther to remove the piston slap would be no big deal, but if the fix is only temporary, it'd be a waste of time. Basically I already figure tearing the engine down for only the slap isn't worth it. What I'm getting no feedback on is the piston slap fix.

 

Google it. I found a couple of people who did go through the trouble and had it come back albeit after much longer miles. When I had my HGs done recently, dealer said that the best way of ensuring that piston slap never comes back is to install a new short block and that other fixes are generally short term. I even called a subaru specialist on west coast to cross check this information. Bottom line: to fix that piston slap you are gonna have to go a lot farther than just spending a little extra money if you plan to solve it permanently.

I did not bother fixing it. I only consider it as a very mild annoyance for ten mins after start up. Plus it reminds me I am in my Subie

 

I have read this thread, and also the "definitive piston slap question"

here we go :
2005 outback, EDM (made in japan) , 2.5i EJ253
265,000km (160Kmi )
timing belt was serviced last year at 240,000km (with new belt tensioner)

started to develop tipical piston slap noise last winter at 240,000km , on cold starts below 5°C or 10°C (40 to 50°F)
noise goes away when water temp reaches 80°C (170°F), that's 5 to 10 minutes of slow drinving depening on how cold it started from (trying to stick bellow 2000RPM in the meantime)
at this point : no significant noise bellow 1500RPM on 10°C cold start

side note : this engine is burning quite a lot of oil, and it's getting worse every other 20,000km

should i start to save €€€ for a new short bloc before this one fails on me, or just keep feeding it with oil and call it a day ?

eventually install an engine bloc heater ?

 

Just saw this thread.
Had a 02 outback that slapped all the time no matter engine temp.
Dealer replaced #2 and #4 piston on the DS at 58 k under warranty.
Slap came back with in 5 k miles but obly when cold this time. Car never burned oil.

 

Last piston slap I heard was when I owned Corvair in early 60s... ever since, I just ignore it or switch to a different (heavier) oil. Never had any problems ever since...