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#6393 of 19283 piston slap redux
Mar 17, 2006 (12:41 am)
I've spent over an hour searching the forums about the dreaded piston slap and really didn't find the specific answers I was looking for.
I have a 2002 Forester and have the "piston slap when cold" problem. I'm planning on selling the car to a neighbor. I'm also considering getting a new Forester.
The first problem is I don't want to sell the car to a friend when it makes that kind of racket during that first 15 minutes it takes until the engine warms.
Question 1: Approximately how much would it cost to repair this piston slap problem? ...ballpark figures gladly accepted. I've gathered there are two possible solutions. Replace 2 of 4 pistons or go the short block route.
Question 2: Is the piston slap situation still a problem on the 2006 models? I don't really want to have this happen again.
This piston slap problem just happens randomly to Subaru engines? There will be some that never develop the problem?
Thank you in advance for any answers!
Mar 18, 2006 (8:11 am)
My youngest son put a penny in my tape deck and now the audio no longer works. How do I remove the radio so I can extract the penny. Oh I checked the fuse for the radio and audio and it is not shorted out.
#6395 of 19283 Re: piston slap redux [scirocco22]
by Mr_Shiftright HOST
Mar 19, 2006 (9:33 am)
You can't replace the pistons without boring out the cylinders. A short block is the only way to fix piston slap...or you can put in heavy oil, some additives and just drive it...they can run a long time with piston slap.
The problem is not only that there is too much clearance between the piston and the cylinder wall, but also that the cylinder wall has probably become oblong (bulged in the middle)...it's not only theh piston that wears (collapses, basically) but also the cylinder wall.
It's probably a metallurgic defect that comes up in the production process and not all engines will necessarily be affected.
#6396 of 19283 Re: piston slap redux [scirocco22]
Mar 19, 2006 (11:18 am)
In an attempt to reduce mass, many mfgrs have trimmed the piston skirt, the part that extends down below the wrist pin. One down side is that the shortened piston can develop some lateral motion within the bore, a kind of vibration that gives that tick/rattle sound. Once everything expands to full diameter, it goes away and the piston moves more smoothly. Subaru is not the only one with this issue, and that has been documented by other sources as well. And of course not all Subi engines do this. A thousandth of an inch here, a thousandth there, and the conditions are just right for this resonance. Mine does it for a full 15 minutes on zero degree days, a minute or two at 30'F, almost none on a warm start.
A few members of this board have pushed SOA to do something in cases were their rattle would not go away or was to the extreme. IIRC, Mark and others (?) got pistons 2 & 4 replaced with slightly oversized units. There may also have been a longer skirt part number that was available at one time as well. If you are under the 5yr/60k warranty, I encourage you to push your dealer for an answer.
I am not sure that any cylinder honing was needed at the time. I seem to remember that those that saw the walls and pistons said that there was little or no visible wear pattern. I have also not heard anyone complain of a loss of compression or increased oil consumption associated with this - just noise. You would think that if there was scoring occuring, compression and oil consumption issues would be telltale signs. Same with oil analysis. A few members did this, and reported that aluminum was up, but not significantly.
While I was also concerned, and visited my dealer when my car was younger, I'm pretty convinced that this is more "cosmetic" than a functional problem. I'm sure that the rest of the crew will jump in here if my memory of details is false (or I'm 'fibbin)!!
#6397 of 19283 Re: piston slap redux [fibber2]
by Mr_Shiftright HOST
Mar 19, 2006 (5:28 pm)
Sure okay if there's a known issue with the piston manufacture, that could explain it....for whatever reason, the piston is wobbling around in there...too much clearance. Never heard of a slightly oversized piston though...maybe what they do is knurl a standard piston to plumb it up a bit.
#6398 of 19283 Re: piston slap redux [Mr_Shiftright]
Mar 19, 2006 (9:21 pm)
I need one of the half dozen or so members who have had it done to jump in with further details. I understand that there is a distinct P/N for the replacement piston assembly.
#6399 of 19283 Re: piston slap redux [fibber2]
Mar 20, 2006 (7:02 am)
I can't address that, but I can tell you that I had my shortblock replaced under warranty on my 98 OB. Within a year the piston slap started to return. Mine only did it when the engine was cold. It disappeared as the engine warmed up. The replacement block was the same way.
I think I ended up with a second short block that had the same tolerance issue as the first. I never determined if Subaru finally addressed it in the short blocks they were sending out, or if it was just the luck of the draw.
I think I would personally go with the piston replacement if I had to do it over again.
#6400 of 19283 GL: power stays on when key removed
Mar 20, 2006 (7:19 am)
Hope this is the right forum. If not, a drop-kick in the correct direction would be appreciated.
My son has a 1988 GL Hatchback. We have recently discovered that when he turns the ignition off and takes the key out, power remains on to the dashboard and accessories.
I'm wondering if there might be a relay somewhere sticking on, or if the only solution is replace the ignition switch?
Thanks for all replies.
#6401 of 19283 Re: piston slap redux [fibber2]
by Mr_Shiftright HOST
Mar 20, 2006 (10:49 am)
I've heard of this problem. As I recall the replacement pistons aren't "oversize", just have longer skirts...
here's a discussion of the issue: (hope this is helpful)
Personally, it sounds like a dubious solution. If I were going through all the trouble of busting down an engine, I'd just do it right....Subaru doesn't want to spring for a short block so they give you this alternative, but really now......
#6402 of 19283 Re: piston slap redux [scirocco22]
Mar 20, 2006 (12:22 pm)
Shifty has already given you a link to a discussion on this issue. I found the information there helpful when I was fighting with my dealer on this issue about 3 years ago. There are one or two dead links in this discussion that led me to an old online chat Q&A where an engineer in the business of rebuilding Subaru engines (I think the name of his company is/was CCR engines) offered the opinion that piston slap might reduce the longevity of the engine by 10%.
One of these dead links is to a sight called the "Ultimate Subaru Message Board", you might be able to do a key word search and find this missing chat thread if you become a member.
Armed with this information I successfully insisted on a short engine block replacement in the Spring of 2003 when I had this problem on my 1997 OB Sport. This was covered under the 6 year / 60K Subaru "Assurance Plan". The short block alone, excluding labor, was about $1,350.00
I was pretty adamant because I bought this car with the intention of driving it into the ground and I wasn't going to accept a 10% reduction in the life of the engine which represents a year of use. If you are planning on selling the car arguably it is a known defect you need to disclose and this reduces the market value of the car.
Good luck. I'm curious to know what you wind up doing.