Piston Slap

[Tubeamp]

Hello, nice to meet you all.

 

 

 

This is my first Subaru and I must say what a fun car this is.

 

 

 

I am wondering if I may ask some advice.

I just recently purchased (last Thursday night) a 2000 Impreza 2.5 RS sedan. It has 140,000km and seems to be experiencing this piston slap issue. Honestly this noise wasn’t present when I test drove, or drove it home from the dealer. But with that being said, the car was already up to running temp before I drove it each time… so no noise right. Noticed the noise the very next morning (Friday), left it for one more morning start up to verify. Called the dealer (Trento Motors) (Toronto, Ontario, Canada) and told the salesman about the problem, as well as commented about the temperature being up before I had driven it (both test drive and pick up). He proceeded to tell me to call the service department to make an appointment. He did not want to help me out with this situation…

 

 

 

I’m bringing the vehicle back to the dealership Monday to have this problem looked and verified if it actually is piston slap.

 

 

 

So my questions are: What can I do about this, if anything? Also, at the worst case scenario, how much of a cost am I looking at for the repairs if it is piston slap?

 

 

 

Thanks for your time,

 

 

 

Rino

[Commuter]

If you have piston slap that goes away when the engine is warm, neither the dealer or Subaru of Canada are going to do anything for you. You may be handed the following "Shop Talk".

 

Subaru Shop Talk No. 02-02-97

 

Engine noise.

 

In 1997, Subaru engines (1.8, 2.2 and 2.5) are more fuel efficient, more powerful and have a flatter more usable torque curve than their predecessors. To achieve these seemingly opposite objectives, it was necessary to bring many improvements and modifications to the Subaru engine line up. Following are some of those improvements:

 

1. Mechanical valve lash adjuster (reduces friction)

2. Light weight pistons (reduces inertia)

3. Short skirt, Molybdenum coated pistons (reduces friction)

4. Increased compression ratio (improved power output)

5. Improved cylinder head design (improves cooling)

6. Inertia resonance induction system (improves breathing)

 

The only drawback to these enhancements may be some engine noise after a cold start-up. This noise is a consequence of the engine improvements and is not a precursor to future engine problems.

 

If a customer complains of cold engine knock, please reassure him/her that no permanent engine damage will occur. If the noise persists and is still clearly audible when the engine is warm, please consult your DASM.

 

Please do not hesitate to contact your DASM if you should have any questions or comments.

 

SUBARU CANADA, INC.

---------------

You would have the Phase II engine, but it still pretty much applies.

 

The general consensus on this board is that if it goes away when the engine warms up, it really won't do any harm. Other makes suffer from this as well. My ex's 99 Honda Odyssey with the 3.5L V6 engine developed piston slap as well before hitting 100k km. Oh well.

 

Commuter

[gbhrps]

Tubeamp,

 

Buyer beware! Unfortunately the dealership in question took you for a ride, and purposely had the engine warmed up before your test drive, knowing full well that the engine had piston slap. Obviously you'll want to be dealing with a more reputable dealership in future. That's the bad news. Here's the good news. My 97 OBW developed the piston slap at 23 000 km, and I went the route of every possibility with the dealership to get to the bottom of the issue. The end result was that at 169 000 km I traded the car on an 02 OBW, (that at present has 104 000 km on it and no slap). All of the time that I owned the 97, it never once let me down, nor did I fear that it would. The slap noise never got any worse from 23 000 km on, and always went away when the engine was warmed up. If you check the archives here you'll find that the slap is an annoyance, but will not affect engine longevity. You'll have to decide whether you can live with it or not, but the dealership you purchased the car from has demonstrated that their business practices are less than honest. Sounds like they need a whole lot of free advertising.... all of it bad!

[Tubeamp]

Hello,

 

 

 

Thank you for your responses. I feel a little better about this noise, being that there doesn’t seem to be any real affects other than the annoyance factor.

 

 

 

You are right, buyer beware… but to be honest, this car is still fun none the less. Have to keep my right foot in check though… very easy to “play around”. And will probably end up putting a new short block in it eventually. Other than the piston slap, this car is in fantastic shape, and I didn’t pay that much for it… considering. Though, I can’t knowingly sell this vehicle to another person… to me, two wrongs don’t make a right.

 

 

 

Funny, my roommate just purchased a 97 Legacy with the same symptoms… huh, how many of these 2.5’s are there with this problem I wonder…

 

 

 

If I was going to replace the short block (or serviced), could anyone point me to a reputable dealer or mechanic in southwestern Ontario?

 

 

 

By the way, if anyone would like to know. The dealer in question is TRENTO MOTORS, Toronto, Ontario.

 

 

 

Thanks again,

 

 

 

Rino

[cookie]

90,000 mile mark the piston slap issue became a bit worse. I have cut it down to when the car is just started by using Mobil 1 15-50. This oil might be too heavy to use in a lot of climates. The car used to slap any time it was below full operating temperature, and now it only slaps for about 30 seconds when completly cold.

I thought about changing the pistons to cure it, or changing the entire block. Folks here tell me the car will slap on merrily for many thousands of miles. This has pretty much convinced me it is just a characteristic of these engines, and I have lived with piston slapping diesels for many thousands of miles. I guess I can live with this one too.

A number of car manufacturers are having slapping issues these days and it seems like the best remedy will be to turn up the stereo on start up. I am going to have my oil analized next time to find out if I should be concerned about this issue. If the oil is full of aluminum...

[meprntr1]

Can someone tell me what excalty does piston slap mean. Having a slight ping/knock in my engine. Is this what my problem is? I have posted this recently but maybe it's piston slap but don't know for sure.

[cookie]

Piston slap is the piston rocking on the wrist pin and having the lower part of the piston skirt hit the cylinder wall. I am sure somebody else can explain this better than I can, but this is caused by a short piston skirt and excessive clearance between the psiton and bore.

 

On Subaru's later engines if it goes away when the engine is fully warm Subaru figures it is fine.

If the engine keeps ticking when warm it may be valve gear.

If the engine makes a pinging sound on throttle application when pulling it may be a condition known as ping, or detonation. This is also slapping the piston skirt against the bore, but the piston is rocking because of preignition.

[richierich]

Very good advise from Cookie and Commuter, not much more to add.

 

Just to let everyone know, I merge these topics because they were on the VERY same subject. We try to keep new topics down to a minimum because they push all the topics down. We have a pretty good search function, and I recommend that newer users try that before posting new topics. A LOT of knowledge can be found in these pages by using the search function. Though I can see why Tubeamp posted, cuz he was concerned about the new car he had just bought.

[Snowman]

My mom's 97 OBW with the EJ25 developed piston slap at around 130,000 km. Switching to Mobil 1 seems to have lessened the noise slightly (now I just have to fix the oil leaks:rolleyes: ). It now has 150,000 km and is running stronger than ever.

 

I'm not positive about this, but I imagine that it would cause less wear/damage if the car was driven gently until it reached operating temperature.

[Tubeamp]

Hello all,

 

 

 

Just wanted to let everyone in on what the dealer said about my piston slap issue.

 

 

 

Basically, I was able to talk to the owner of the dealership. He gave me 3 options.

 

 

• Full refund
  
• Will split the cost of the two new pistons/parts and the labor (pistons on one side of the motor, not changing other side) (costing me $600)
  
• Have Subaru Canada assess the motor, if it does not meet their specification, replace.
  

 

I think this is more than fair of this man. Trento Motors (Ontario, Canada).

 

 

 

If this was you and your vehicle, what would you do?

 

 

 

Rino

[nipper]

Thats a hard one, i think i would choose #2, as i am pretty sure subaru will say its normal.

 

 

nipper

[The Dude]

I have a 99 Forester. My car has had piston slap since 60,000 miles, it now has 191,000 miles (305,600 km)

 

1. Piston slap can get VERY loud in cold weather, Canadian guy. It will quiet down considerably after the engine warms up.

2. The piston slap will get worse with mileage. Not louder, but at start up the engine will have the slap at higher and higher outdoor temperatures.

3. I don't remember anyone on this board reporting engine damage as a direct result of piston slap.

4. I don't think piston slap, in itself, damages or significantly reduces the life of the engine.

 

So, in the dead of a Canadian winter the slap will be really LOUD, like a bad main bearing, until the engine warms up. Given your climate, you might eventually have piston slap at start up for five or six months out of the year.

[cookie]

I would grab it in a heartbeat. I have even been considering paying full price to do it on my car. I am sure that would be a couple of grand before you are done.

I have also considered tearing it apart myself to do it, in which case I could probably beat the $600, but I am not sure I am that ethusiastic about getting down and dirty anymore. I also considered ordering a new turbo block which I imagine would set me back around $4,000 by the time I got it in the car.

In the past I would have gone one of the above routes, but now I think that I may as well let it slap. It seems from the experience of friends on this board that the only thing I'll have to deal with is an irritating sound when cold for as long as I am likely to have the car.

[The Dude]

I am with Cookie. If piston slap is the only issue with the car, I would buy it. Your roomie, on the other hand, has a car with the infamous 2.5 DOHC engine. That engine has well known head gasket problems. At least you can give your roomie a ride if the head gaskets blow.

[brus brother]

Well, I'm not as inclined to just say yes to their "kind" offers. I have a 2000 Legacy GT with 75,000 miles without any slap. If you absolutely love the car and feel the deal was a good price then I would negotiate with the new and improved pistons x 4. This will give you the peace of mind that the future will not bite you on the other cheek. They know the car was prepared for you so as to not slap when you tested it and likely hoped you were deaf or dumb or both. They don't want the car back so, ask for a wee bit more good will at this point. What can they say... no? Not likely, call their bluff.

PS Short block is about $2000 US plus install

Hello all,

 

 

 

Just wanted to let everyone in on what the dealer said about my piston slap issue.

 

 

 

Basically, I was able to talk to the owner of the dealership. He gave me 3 options.

 

 

 

 

• Full refund
  
• Will split the cost of the two new pistons/parts and the labor (pistons on one side of the motor, not changing other side) (costing me $600)
  
• Have Subaru Canada assess the motor, if it does not meet their specification, replace.
  

I think this is more than fair of this man. Trento Motors (Ontario, Canada).

 

 

 

If this was you and your vehicle, what would you do?

 

 

 

Rino

[idosubaru]

no way i'd spend that money on 2 pistons. i would only consider new pistons if they are a new design that prevents this problem. no way i'd go through all this with the possibility of a recurrence. if there is a new piston design then i'd be tempted to go for replacing all 4, replacing 2 is nonsense after hearing that others have developed the slap after 100,000+ miles.

 

considering what is involved in replacing pistons - replacing 4 instead of 2 is such a small difference in the overall job time, do them all.

[cookie]

but I have been told that the 2 replacement pistons have a modified skirt. The reason they fit them on only one side is that due to the boxer design only one side is the problem.

Since I've never seen them myself I cannot confirm this.

[nipper]

hrmmm ok yes there is a service bullitin that states they have a modified piston for slap. That said, on an opposed engine, the reason why they last so long is that all forces are equall and oppisite, and therefor cancel themselves out.

 

What kind of warrenty will the dealer give you on the work?

 

nipper

[Setright]

Ermm, Nipper those forces are "absorbed" in the bearings, crankshaft, and crankcase, not cancelled out.

 

The boxer/flat design only means that the engine vibrates very little - pulls smoothly past 6000rpm.

[nipper]

http://www.absoluteastronomy.com/encyclopedia/f/fl/flat_engine.htm

 

The benefit of using an horizontally opposed engine engine versus a V engine is that it provides perfect balance because each piston's movement is exactly counterbalanced by the corresponding piston movement of the opposite side.

 

equal and opposite forces cancel out.

 

They cancel out, they are not absorbed. and actually forces are never absorbed in an engine, but are cushioned by the thin layer of oil on the crank journals.

 

nipper

[cookie]

The way I see it this engine layout is not exactly equal. The crank only turns one direction and the intake is on the same side (top) on each side. This is bound to mean that cylinder filling and fireing are not going to be exactly equal. I think the reason Subaru may have issued only two pistons in this upgrade is that one side fires a bit different and has slightly different stresses leading to slapping on one side only.

I think I can hear this with my stethascope. No senile jokes and I am sure Blitz will soon tell me it has something to do with black helicopters and right wing conspiracy.

[nipper]

Actually i didnt want to open that can of worms. Its been ages since I have blueprinted and balanced an engine, so i dont know how much the new pistons differ from the old pistons in weight.

I do however put alot of faith in subaru on somethings, since it seems like a very rare (if ever) post about an engine spinning a bearing, either a main or a connecting rod bearing.

This is the reason I buy subarus, I love the opposed flat engines, I cant afford a porsche, I dont want a vw (hehe imgaine 45 HP in todays world), but i will have another corvair

 

nipper

[blitz]

It's left wing conspiracy.

[cookie]

I am getting more and more confused as I age toward Republicanism. If I wasn't confused enough Bush really hasn't helped. WMD, no WMD...

Come on Blitz, what do you think about the slap?

[blitz]

POLITICAL RANT ON:

Frankly it's both parties, technically a criminal conspiracy if you will ...a power struggle between various wealthy global factions that instinctively masquerade behind nationalism (because it's a highly effective means of swaying the peasant groupthink).

Both political parties are crooked as hell. Elected representatives are in the pockets of the global corporate interests. They don't give as rat's rectum about their constituency.

POLITICAL RANT OFF:

 

Now that I got that out of the way IMO the only difference between the left bank and the right bank (from a mechanical standpoint) is the direction of the force of gravity relative to the thrust surface. The left bank has it's thrust surface facing down toward the ground (with gravity) and the right bank has it's thrust surface facing up (opposing gravity).

 

I wouldn't seem unreasonable that the wrist-pin postion of upward-facing bank's been shifted slightly on the "countermeasure" pistons to help offset the rocking (slapping) motion. Cookie do you happen to know which bank Subaru replaces with the improved part? I'm thinking the right side.

 

Was it Chrysler (back in the 60's?) that used to have a motor with an offset pin to combat a slapping problem, the trade-off being a certain amount of power loss? Racers would turn the pistons around to pick up 10 hp and a whole-lotta slap.