Picked up my car from those dudes at Cheam Motors (actually, my car was delivered to my house).
They have confirmed they will fit a new short engine for me http://bbs.scoobynet.co.uk/smile.gif

Ill keep you posted

Current situation is as follows.

My car is being inspected on saturday morning for the dreaded Number 4 cylinder piston slap.

My dealer is being very helpfull, trying to inconvenience me as little as possible. My car is already booked in for repair next thursday, subject to the inspection confirming what we all know the problem will be.

I am not at all happy with the only fix that IM will authorise, that of stripping the head off and fitting a new number four piston, then rebuilding the engine.No checks for bore wear at all!


I spoke to john baker, one of the technicians at IM and told him i was not happy with this fix. He told me that the only way this could be improved upon would be on the authority of Mr Brian Pimm, technical service director.

I spoke to Mr Pimm and explained that i was unhappy with this fix as there will be some damage to the bore due to the piston slap wearing it oval. He was very agresive at first and talked at me like i was an idiot. For those who know me from the BBS, the one thing i understand is how engines work and how they go wrong.

I asked him why the policy is to fit a new short motor to the turbo model and yet only a piston on the sport. I did not get a satisfactory answer.

I asked him why this problem was occuring in the first place. He said that there is no official explanation from subaru but they believe it is caused by the Number 4 cylinder running hotter than any of the others, causing the piston to distort. It shows up at about 8000 miles. My car has 8500 miles on the clock and i started to notice the problem at about 7800 miles.

I explained i was unhappy about just fitting a piston as i would expect that in the future, possibly out of waranty period the rings may fail due to uneven wear. He said that they had never had a problem with a non turbo engine once the piston had been changed and if i had a problem a few years down the line that was related to the number 4 cylinder they would sort it. The problem with this is that if i sell the car to someone else and they have an engine failure outside the waranty period, would IM sort that free of charge?

I asked why they wouldn't fit a new short motor to the car like they would with the turbo and he said that it would most likely fail in the same way in another 8000 miles.

I asked him why he wouldn't fit a 99 spec engine in the car then, as this is a different design. He said that because it was a different design they would not fit it in a 98 spec car, i am totally confused on that logic.

Anyway, to wrap it up, i am less than impressed with the events today but am not going to get any better response from IM from this so i will have to go with a piston change only, so much for the legendary support subaru are supposed to offer. I am stuck with an engine with a fudimental design flaw which i feel is a time bomb for someone down the line.

This is not a reflection on my feelings towards the dealer, they seem a really dedicated bunch of people who have their hands tide behind there backs. They can only do what IM allows them to do and are trying to minimise my inconvenience.

yours well pi$$ed off

john

John...

Sorry to hear about the crap service from IM

Measure the bore.. and thoroughly check for wear before the piston is put back in.

I always believed wear is associated with slap (best to edge on the worst side)

If you find wear, then you stand a great case of a new "short".... if not, then I am afraid you are stuck... http://bbs.scoobynet.co.uk/frown.gif

If they claim it to be a piston fault, are they a new design of piston ? If not, then you have another problem - will it fail again in another 8K ?

I have a set of STI pistons spare...no det lol

J.

Ohhhh dear, this doesn't sound good. I got confirmation from my dealer that my car's booked in to get a new short motor, 22ndfeb2000. They've been reasonable helpfull although they don't give the impression that the job will be done as well as it could be? I asked a few questions:-
When are you ordering up the short motor? Oh, we don't do that until your engine is appart.
Why? So that we can make one order to Subaru as opppsoed to lots of seperate orders, we don't know what we'll find, until we get in there.
How often do you do engine rebuilds?
Once a year - ish.
I'm a car enthusiast, I build my own race engines for minis and I compete every year in motorsport, can I come around a see the engine in bits and have a quick look at the damaged parts?
Silence.

So, I'm going get more info, I was told a new short motor would be fitted. Why would they want to take the old block apart if they've got a new short motor to fit? My dealer tells me that the short motor comes in kit form. I must admit I'm suprised at that?

Put in this way, if it turns out that there doing the one piston trick, I'll be far from happy. A decision to go this route doesn't give me that feeling of engineering excellence, it's a short term fix until my warranty expires.

New short motor, that will mean new engine number?

As soon as I get more info, I'll let you know.

Okay, spoke to my dealer and they confirmed that for my car I'm getting a new short motor that comes already built from the factory. I also contacted another dealer, they also confirmed that this should be the case. So basically he was speaking nonsense when I was told it comes as a kit. Depends how you define kit? Both dealers mentioned that the one piston repair is usually carried out on Legacy's.

Also explained was that no4 piston gets hotter than the rest of the engine and this is probably the route of the problem.

The replacement short motor, is expected to be to the latest spec and not just the same new.

Dealer hadn't thought about engine number and is looking into it.

I'm happy with the explainations and proposed repair, I'll let you know how it goes.

Jon, is yours a turbo or a sport?

[This message has been edited by johnfelstead (edited 11-02-2000).]

John,

is there not also potentially a balance problem with just fitting one replacement piston?

Particularly if different design?

Maybe something else to consider.

Best of luck

Scott

Hi J,

The message i am picking up is that there isn't a piston design fault, it is the fact that the block design leads to number 4 cylinder running hotter than the rest, this leads to the piston in number 4 overheating and then distorting perminantly.

The fix is to fit a slightly different piston in the effected bore to compensate for the inherant block design flaw. I would be interested to see this piston to see if they are coating it in any ceramics to reduce the heat transfer and therefore the distortion.

I wouldnt have a problem with running a brand new block with this new piston from day one as no damage to the bore would have occured.

The thing that is anoying me is that the fix is being done after damage may have occured to the bore, something i would never tolerate in any of my race engines.

I have thought about this problem and it only effecting the one cylinder, No 4, and can think of only 2 reasons that it would occur.

The first is that there was a honing machine setup problem at the engine factory that lead to the No4 cylinder being incorrectly sized and this was not picked up for a long time. I think this is unlikely.

The second is that there is a deficiency in the flow of the cooling water around the Number 4 cylinder due to a design flaw that again was not picked up until a large number of blocks had been cast. I think this is more likely.

I did a lot of work on prototyping a new cylinder head design for a race V8 engine and the cooling design was very complex and difficult to perfect.

I would be interested to know what changes were made to the 99 spec engine in the cooling dept/block waterway design to see how they cured this problem.

I would be very interested in checking the bore with my bore gauges to see if any damage has ocured but would be surprised if i am allowed to do that. Even if i do find a problem it seems that i will be stuck with the piston change fix anyway, based on the attitude of IM.

The thing that doesn't add up is why they feel the turbo has to have a new short motor yet the sport doesnt, the basic physics are identical.

Sti motors have balanced pistons etc as they are blueprinted. UK cars are just whatever comes out of the production bag though so no issues there unless the design is different significantly.

Jon

Just out of interest ask them which cylinder they say is no 4 ?

[This message has been edited by Bob Rawle (edited 11-02-2000).]

No 4 is rear passenger side pot.

Another thing that struck me this morning is that the impreza block has a little removable blanking plate on the side of the block on No 4 cylinder.

I didnt notice wether all cylinders have this or just No4.

This plate is there so that when it is removed it allows access to the gudgeon pin circlip when the piston is at bottom dead centre.

To change the piston you simply remove the head, remove the side plate, remove the circlip, slide out the gudgeon pin and pull out the piston. To put a new piston in you just reverse the process. Very quick and easy, no need to touch the big ends, strip the block etc.

This is a great design if you are expecting to have to replace the pistons before you did a full engine rebuild, where you would inspect/change the mains/big end bearings and rebore the cylinder etc.

This is the first engine i have ever come accross that has had this provision in the block.

It leads me to think that subaru knew there was a problem with the design of this engine and put in place a way of doing a quick fix which would minimise the labour time/parts used to fix the problem on the engines that showed up a defective.

What do you think, am i being paranoid on this one.

Oh dear,

Just had the car inspected at home by the local dealer.
It sounds more serious than the piston slap problem. http://bbs.scoobynet.co.uk/frown.gif
The car is going in next week to the dealers to investigate further.
Not sure what it is but the testing that is normally done to identify that it is piston slap showed that it could be something more serious. http://bbs.scoobynet.co.uk/frown.gif
I will have to wait and see what the outcome is of the inspection and then get back to you.

oh bugger. http://bbs.scoobynet.co.uk/frown.gif

P.S. this still doesn't change my attitude to the piston slap fix issue, that goes against all my feelings as to good engineering practices.

John,

I presume that when your dealer was going to fit the new piston, they would check the bore for ovality and tapering - assuming these were ok, what would be the problem replacing a piston?.

Did the dealer give you an idea what the more serious problem might be? - you might get a new short motor after all.

Let us know what develops.

Cheers,

Alex

Hi alex.

The dealers were not going to check for any ovalty or taper wear, just put a new piston in irespective as that is what IM tell them to do.
That is one of the reasons why i was so unhappy with this fix.
I am not going to pre-judge what is going to be the outcome of this as what i thought my car was suffering from, piston slap, which is well documented on this BBS, is not the cause of my problem.

I will let you know what the inspection on thursday determines.

John, thanks for the "No 4" info. The blanking plate idea has been around for years and is/was normally built into all cylinders for the reasons you suggest, also some older engines (mainly motorcycle) could have their big ends changed by this method. I agree with you, however, that its quite "odd" that a modern high performance engine should have this on just one cylinder. However to "design it in" means that they designed the problem as well and knew about it. The tooling mods to allow its introduction would have been relatively expensive and so they should have been able to fix the problem, whatever it is, by retooling to overcome a design limitation.

hi bob.

I didn't say that only no4 had a blanking plate, i said i did not notice it on the other 3 at the time.

After thinking about it more i have to agree with you bob on the fact the tooling costs for putting this plate there would be massive and that the same resources could be utilised to fix the original problem.

I have never seen this on any engine i have worked with before, and the list is quite long, but i dont profess to know everything, i think it is a great idea if the need to change pistons is required before a full engine rebuild but am surprised it is used on a modern engine.

There could be a reson for it on the production line of course if it is easier to assemble the engine block with rods, crank etc before the pistons go in.

Is there anyone out there that knows why these plates are there?

Getting back to my original reason for posting on here, it worries me that a piston can be installed into an engine as a fix, without fully investigating if any damage to the bore that the distorted piston was running in has had any serious damage, each and every engine with this problem should be checked for excesive wear with bore gauges. Every failure has different charicteristics, even when following a know pattern. If the bore has no ovalty or taper then i would not have a problem with fitting a new piston, i do have a problem with fitting a piston in a bore that you dont know the condition of.

Hi guys..

You can change the pistons with out splitting the block.

You access the pins via the blanking plate access. You can do this for all the pistons.

The trick is to tip the engine on its end... so the rods dont drop down.

Its fiddly.... Subaru have a special tool to reach inside... Its a good design...

Anyways... I'm full of uslelss info... tara

J.

ps - One solution to ovality.... have an oval piston fitted.. http://bbs.scoobynet.co.uk/wink.gif

[This message has been edited by firefox (edited 12-02-2000).]

Bob...

When I say Oval.. I mean "Oval" http://bbs.scoobynet.co.uk/wink.gif

lol

J.

John, I agree with you that this is very "odd" as an approach to a modern engine design.

Firefox, how oval is oval ? ..... lol

Bob

Hi,

Maybe (as Firefox suggests) it is less trouble than splitting the block. I can't imagine it is so bad that you wouldn't want to check out the bottom end or rehone the bores when you need to replace pistons though...

Didn't Honda run a 4-stroke world superbike engine with oval pistons? it was blown away by the two strokes though...

Cheers,

Alex

[This message has been edited by AlexM (edited 13-02-2000).]

Just thinking about machining an oval piston ..

Bob

John,
What does piston slap actually sound like?
My STI now I've had a 30k done on it, the rattle on cold start is much quieter but the flapping noise, most noticeble at idle to 1200rpm (in neutral) sitting in the drivers seat is still there. It sounds a bit like a helicopter hovering overhead - seriously! but not as loud. As rpm's are increased slowly, the flapping noise is masked out by the normal engine noise.

weird!

cheers
Howie

John,
My car's a 97turbo, first of the face lift models, mk2. Listening to my engine I would have said that no4 was passenger front, but it's hard to tell. Definately passenger side. Noises are difficult to source and describe, but on saying that my engine when cold sounds like a big end has gone. It's definately a thud like knocking sound and sometimes it sounds worse in the car than from outside? I'm not an expert on the subaru engine, but I would not have desribed the noise as piston slap?


So it's more serious that piston slap, what do think's wrong with your engine?

Latest news, no engines available until the end of March2000. Great.

i am not going to comment on what i think it is as that would be pointless.

I will wait and see what the investigations actually find is the fault.

all i can say is that the sound proofing on the scooby must be very good.

When we were testing my engine for piston slap when cold my engine sounded bloody awefull. It is more serious than a slap problem on mine im afraid.

on the cars i have heard piston slap on it is a low frequency thud come low frequency rattle. Its hard to describe realy.

See what you've started Cem...blimin boy racer....you are solely responsible for all these peoples engine claims.....IM ought to confiscate your dump valve http://bbs.scoobynet.co.uk/wink.gif http://bbs.scoobynet.co.uk/wink.gif

[This message has been edited by sunilp (edited 14-02-2000).]

Got my scooby back this afternoon.

IM authorised a new MY98 short motor and the modified No4 piston has been fitted. So now have an engine which shouldn't slap in 8K. http://bbs.scoobynet.co.uk/biggrin.gif

The local dealers have done a cracking job and have kept me informed with what was going on.

The thing that really winds me up is not being told the truth about what is going on, my dealers were very good on this, a happy skooby driver again http://bbs.scoobynet.co.uk/biggrin.gif

Just off to scotland in the morning for a couple of days to run it in, john O'Groats is the plan.

cheers
john

John,
It sounds like you've had the short motor fitted already? If so, how did you manage that? I just called my dealer and no engines for perhaps 2weeks yet?
Is it just No4 that's different? What happens with engine numbers and log book? Did you get the old engine, I was going to ask?

As a result of this thread, I had my car checked out at Cheam motors as part of the 45,000 mile service. Guess what - I need a short engine (my car's a MY97). They expect to carry out the work in the first couple of weeks in March.

i got my short motor within 1 day of the inspection, my car is a 2.0i sport, not a turbo. That maybe why you have to wait.

just got back from running it in by going to john O'Groats then over the top and down the west coast. Great run.