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Discussion Starter #1
My '02 has 116k miles. I have a hollow knocking sound on cold start, I knew I needed to adjust the valves anyway so I did it a few weeks ago. The knocking is still there and I'm pretty sure it isn't valve noise. It does diminish when the van warms up. My next thought was piston slap. After doing some searching on the forum, I'm leaning towards this being the issue. So, who else has piston slap? If you do have it, is my description of a hollow knocking sound accurate?
 

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Usually, piston slap is “engineered out” by offsetting the wrist pin from the piston’s centerline. I don’t think they would slap unless one or more were extremely worn. Knocking from engine block? Could be a rod bearing.
 

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Discussion Starter #3
Thanks for the reply. I really don't think it is bearing noise. Seems like others have noticed slap on their engines with less mileage than mine. I'll do some more research, but I'm thinking slap is the likely culprit.
 

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Many of them tic when cold and it fades when it comes up to operating temp. Very common and doesn't seem to affect anything. I would think a bearing or piston slap would not quiet when warmed up :dunno:
 

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\I would think a bearing or piston slap would not quiet when warmed up :dunno:
Piston slap is a Honda thing and not uncommon. My 96 sounds like a diesel in cold weather and very quiet once warmed up. Has since new. :D
Research Honda piston slap and you will find it is a a part of the piston design. ;)
 

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Discussion Starter #6
Thanks for the replies. It isn't ticking, and it isn't valve noise. I can isolate it to the block by listening with a steel rod.

It makes sense to me that piston slap noise would diminish as the block warms up and expands. I'll keep an eye/ear on it.
 

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Discussion Starter #7

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Piston slap is a Honda thing and not uncommon. My 96 sounds like a diesel in cold weather and very quiet once warmed up. Has since new. :D
Research Honda piston slap and you will find it is a a part of the piston design. ;)
Interesting, ok then. I know my cold engine noise sounds nothing like a bad bearing. Been there, not so fun.
 

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Well, I have both a 2001 Odyssey and a 1996 Civic 1.6 (SOHC non-VTEC), and they both make noise at cold startup, with the Civic being much worse and for longer before quieting up. I know that some of the 1.6 engines had issues with the pistons being a bit undersized which would contribute to the noise.
 

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:frown:Yep, it's piston slap! My 02 has been making the same noise for over 100,000 klms. It's to the point that it never goes away, just loud and louder. In winter conditions the noise is constant and changes only with the viscosity of the oil and temperature. Summer is not as loud. I really dislike the noise but on the road who hears it? There is no affect on performance and obviously no affect on reliability.Shame on you Honda, you promised better and didn't deliver.
 

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Shame on Honda for what? A noise you can't hear while driving? The pistons are made oval shaped to reduce cold start friction and round out as the heat up. I have 187,000km on our 96 and it is amazing how loud it can be in winter and a cold start. Never got worse from new, no harm no foul. To each his own.
 

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Discussion Starter #12
I don't consider this something that I'm blaming Honda for. My engine has 116k miles and wear is a fact of life. The design of the engine and pistons probably makes them more subject to slap as I don't believe the pistons have long skirts and the geometry may subject the block to more sidewall loading than some engines. I'm not an engine designer, but I realize it is all a trade off between friction, power, costs, durability, etc. My van is fine, I now know what the nose is, and I'll live with it.

Now if my transmission grenaded at 60k miles, that's another issue. :D
 
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