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As the third winter for this 2.5 Litre, 76000 km, 5MT, wagon draws to a close, a worsening engine noise has been diagnosed as "piston slap". The noise is most prominent on cold starts, under load, and is not present at high revs. My research indicates that undersized piston skirts (especially on number 4) cause this noise, and that it does not result in significant wear (perhaps 10% less engine life). Reselling such a car would be problematic. Subaru will now replace the short block. My questions: Will the heavier pistons reduce what has been excellent gas mileage? Will breaking open the engine create new problems? Will the short block be new, or rebuilt? Should I be getting a new timing belt now and should the labour cost be less, since the engine will be open anyway?

If they're replacing the short block they won't be cracking the engine open. The extra weight of the pistons shouldn't affect gas mileage. They just put more stress on the bottom end at high rpms, but these bottom ends are seriously overbuilt anyway.

They almost have to replace the T-belt to do the job, and would probably ask you to do it (they could reuse the old one, but why bother unless it was just done?). I'd mention it if they don't and get the water pump done, too. If Subaru is paying for this, then the block should be new.

FYI, a short block is the block, crank, rods, and pistons as a unit. A long block would add the heads and valvetrain to the short block. They'd do a whole short block over replacing the pistons as the labor's cheaper and quality is easier to control. They just pull the motor, remove the heads and intake, swap them over, and reinstal. I could do one by myself outdoors in a good afternoon.

Steve

Promises, promises! On March 18, 2005, the Subaru dealership in Peterborough, Ontario, Canada, promised to call me when the new short block arrived. The car was also in for it's 72000km service at that time, yet it was returned to me without this service. I expected a call within a couple of months. When I called back in June of 2005, an apologetic service representative, found the defunct order, and re-issued it - along with a promise to call when the new block arrived (estimated at six weeks). That was about twelve weeks ago. The car is now at 85000km. The piston slap started in the first year, before 20000km, and I told them about the noise at that time. I guess I've been crossed off their mailing list and their call list. I'm just one more customer from whom they can save money by not honouring their warranty.

dandelong wrote:Promises, promises! On March 18, 2005, the Subaru dealership in Peterborough, Ontario, Canada, promised to call me when the new short block arrived. The car was also in for it's 72000km service at that time, yet it was returned to me without this service. I expected a call within a couple of months. When I called back in June of 2005, an apologetic service representative, found the defunct order, and re-issued it - along with a promise to call when the new block arrived (estimated at six weeks). That was about twelve weeks ago. The car is now at 85000km. The piston slap started in the first year, before 20000km, and I told them about the noise at that time. I guess I've been crossed off their mailing list and their call list. I'm just one more customer from whom they can save money by not honouring their warranty.

It's unfortunate that some dealerships work in this manner and call it policy.

We, on the other hand are here to help you. If you're so inclined to go digging in the engine bay, and want a fun experience (and hopefully have another car to use while you're working on this one) you can source another shortblock, and drop it in yourself. Before we explain more, does that sound like something you can handle?

go to another dealer. demand the paperwork from the first dealer to prove your case. dealers make a lot of money on warranty work, they shouldn't hate it, they should love it.

Here I am replying to my own piston slap message again. This forum must be monitored by Subaru. On a Friday, I described my difficulties obtaining warranty work. Next Monday morning the dealer phoned, arranging a prompt appointment. The new short block was installed two days later. In fact, if I'd known that the new block carries a 60000 km warranty, I could have waited a little longer. But, I guess that driving around town with a noisy engine is poor advertising for Subaru, so they are just as happy to replace the engine earlier rather than later.
At the same time, the timing belt was replaced at 89000km rather than the recommended 160000km. The water pump was not replaced. The dealer was surprised at the amount of wear still remaining on the brake pads, but the rears had been corroded by three winters of driving. The cost for new rear rotars, pads, fluids, timing belt, taxes came to about $950 CDN.
Anyone want to guess what'll go wrong next? The pressure plate has been replaced already. However, under full throttle in second and third gear, the engine seems to fluctuate in power. The brake pedal sinks suddenly a little bit when the idle speed drops during a long wait at a stop light. It'll need new tires before winter. The dealer recommends Michelin Hydro Edge. A local Toyota dealer recommends the similar, yet slightly cheaper, Goodyear Triple Tred.

one of techs there is now making good use of your old shortblock