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  #16  
Old 10-18-2007, 10:28 PM
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Quote:
Originally Posted by suginami View Post
Why do these engines sometimes need a new block?
As I posted earlier, by the time the driver hears the noise, it's too late. The cylinder walls/piston skirts are damaged.

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  #17  
Old 10-24-2007, 12:02 AM
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So are these engines going to become the equivalent of the 350 rodbenders, or are these cases of premature failure attributed to something other than design flaw? Manufacturing flaw?
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  #18  
Old 10-24-2007, 12:12 AM
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The only car I've ever had with piston slap was a 2001 Corvette Z06. It would rattle like crazy until it warmed up, and still a little after that. Drove me nuts. Those cars were infamous for having this problem. GM modified the pistons as of 2002.

I never did have it fixed. Can you imagine the trauma of having someone R&R the engine in your pristine Corvette that you only drive on the weekend? Who knows, you MIGHT get a good tech in the dealer service dept. But most likely they would break two things fixing the one.
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  #19  
Old 10-24-2007, 12:17 PM
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Quote:
Originally Posted by fahrgewehr2 View Post
So are these engines going to become the equivalent of the 350 rodbenders, or are these cases of premature failure attributed to something other than design flaw? Manufacturing flaw?
I've always been a bit uncomfortable with the FSS oil change interval but what do I know? The majority of fitted blocks I do have had all the oil changes done on time, but just barely. I've been told by MB engineers that the FSS system works well, but sludging will start soon after the mileage interval has elapsed.
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  #20  
Old 10-24-2007, 01:39 PM
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I may be the expert on piston slap: I bought a Subaru Outback 2.5 liter engine (4 cyl boxer) new in 1998. It's an aluminum block with steel liners, so the pistons run on a steel surface. Soon after I bought it, I heard piston slap when the engine was cold in the morning for a few miles until it warms up. The noise also goes away when there is very little load on the engine, like driving downhill. The piston slap re-appears when there is a lot of load on the engine at low rpm. as in towing a trailer uphill. Now the engine is warm. I made big noises to Subaru. They told me:"we know, but it's not detrimental to the longevity of the engine". But the mechanic tells me they have supplied replacement engines free of charge in cases where the piston slap wouldn't go away after driving it a few miles. Now, 10 years later, I have 47,000 miles on the engine, it still makes the noise, but it doesn't use any oil (yet). So, maybe I'm not the expert, but I sure hear it every day. I think, the piston skirt is too short, the piston has a too much clearance and slaps in the cylinder. The aluminum block transmits the noise more than a cast iron block. It's not pre-ignition: That is much louder and scary and happens on acceleration. It's really noticeable even for a dumb engineer. I just did my Honda Trail 90: On a two inch bore I had the shop bore it 1/2 thousand inch larger than the piston. When you do that, the dry piston, without rings, stays in the hole against gravity. I broke it in, in several short high speed, high load runs. We have just the hills here for that. Runs wonderful now. Uses no oil, no smoke.
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  #21  
Old 10-26-2007, 03:28 PM
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From time to time, I hear what I would describe as piston slap coming from the 99. I hear it when going through the drive through next to a building and the window is open. I don't hear it everytime. In fact most of the time the engine is so quiet you can hardly hear it running.
The thing uses no oil. Runs like a top. Starts just fine, and doesn't necessarily make the noise on start up either.

I've heard real piston slap, in an engine that had to be replaced. A GM product. It's not as bad as that was, but I'm pretty sure, based on this thread that that's what I'm hearing.
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  #22  
Old 10-26-2007, 05:00 PM
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I assume your engine is at idle when you're in the drive-thru.

More likely to be a valve lifter than piston slap.
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  #23  
Old 10-27-2007, 08:25 AM
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justncase:

Did you ever find out what the problem was and were you able to fix it?

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