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I believe that my 98 Outback is suffering from piston slap. I've heard this is a common problem. The dealer tells me it's normal, but I don't believe him. I've read that it gets worse over time and it has. I'm now at 52,000 mi. My question is: How long will it do this before something catastrophic (I need spell check for that one) happens? The car has been troube free to this point and the slap is just annoying at the present time.

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I have never heard of engine failure due to piston slap, though I have heard of some people having the short block replaced under warranty for it. Our 99 does it pretty bad when it is cold. It causes me severe mental distress to listen to the thing as I drive it when it is cold, but I don't know that it really hurts anything. I like to let the engine run at least a minute before I go, and then just take it easy until it quiets down. Who knows what my wife does. It doesn't quiet down until about 3 miles after the coolant temp gauge has leveled off.

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Do a GOOGLE Search on Piston Slap. Canadian Driver has a good write up. It's a result of the 'improvements' on newer engines to lighten the piston by reducing the skirt length and changing the shape of the pistons especially alloy pistons, to allow for shape change going from cold start to operating temp. This accounts for why it happens cold and not warm.

It does NOT damage the engine according to anything I have seen or heard or read. And ALL Mfgrs have their share of engine slap these days. Being Subaru has only the 4 and 6 at this time, the 4 definately has the problem. But Toyota, Ford, GM, Mopar, the list goes on....and so do the complaints.

I don't like it, but it seems to be a way of life..........

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It's a very quiet tapping, barely audible (in fact my wife swears SHE can't hear it). Ours lasts about two minutes and never comes back all day.

 

We bought the car with 100,000 miles on it (at 13 months old) and now have 140,000 and it hasn't gotten any worse. Also NO signs of head gasket or auto tranny probs. I believe this is the best car I've ever owned, and that is WELL over the one hundred mark.

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but if I am in a parking building with the windows down it sounds pretty loud.

It is annoying but causes little harm.

When I was a kid we would rebuild engines without enough money to bore them and put in new pistons.

You frequently ended up with piston slap but the suckers would run another 100,000 miles.

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I pulled the head and dropped the pan in our apartment parking lot. The valves consisted of cleaning with a drill powered wire brush and 'lapping' with Ajax paste. I honed the cylinders the same way, with a borrowed honer in the same hand held drill. For the bearings I took the old bearings into an auto shop and bought the next oversize, bolted it together and tightened the hell out of it.

 

It took a hundred feet of pushing it to break the engine free, and another block to get it running. But, it ran great, burned no oil and the guy who bought it from me drove it from SoCal to Guatamala and back and said it was one of the best running cars in the whole missionary group he was fielding with.

 

Then there's the BonAmi ring jobs!

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a block of wood and a sledgehammer?

I did a flathead Ford that way, honed heck out of it. Put in a piston and ring set from a jankyard and drove it till I sold the truck. It burned very little oil all the time I had it.

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My 97 OBW developed the piston slap as described at 23 000 km and still had it at 122 000 km when I traded it on an 02 OBW. The noise was annoying when cold, but when it warmed up (within 3 minutes) the sound was gone. Much worse in winter than summer, for sure. No head gasket problems at all. If I had been scared off by the piston slap or concerned about the head gasket going, I wouldn't have bought the 02 OBW. No slap as of yet in the new one at 49 000 kms, but it is noisier when it is cold outside, until it warms up. This won't be my last Subaru.

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I have a 02 obw that has 31k miles on it .I have had the slap since 6k miles . I have complained to the dealer everytime I had the car serviced . He showed me a TSB from Subaru about the slap . If the noise goes away when the engine is upto operating temp they do nothing about it . I have heard of others that have complained enough about it to have the short block changed and guess what the noise was still there . I just changed my o/f today and I sent a samplee away to have it analysed . I'm hoping that it will show normal wear . I was able to get my DSR from subaru to admit that it was piston slap but as before the noise went away when the engine was warm . To give me some piece of mind he gave me for free a subaru gold warranty with 0 deductable for 7year and 100k miles .I use mobil 1 oil and subie filter every 5-6k miles . I have been using 5w30 in the winter and 10w 30 in summer. The slap is more noticable with the thinner oil in the winter time .I was thinking maybe I'll just keep the 10w30 in yearround . I'll let you all know how my oil tested .

 

Mike k

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