Piston Slap!

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Thread: Piston Slap!

  1. #1
    Walking
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    Piston Slap!

    Hi all,

    Just found GMI and joined. Looks like a great resource for GM/Chevy owners and I'm hoping to share what I've learned (mostly frustrations!) as a newbie Chevy Truck owner, and hear from experts who know the ropes.

    I have recently learned about the infamous condition known as Piston Slap (www.pistonslap.com), and am trying to get the root of the matter in terms of:

    1. Is it really a "customer annoyance" issue, as GM claims in there tech bullitens, or is is a time bomb in hiding? I come from a manufacturing background, and in my humble experience metal slapping metal is NOT good in any case, regardless of whether or not you find it "annoying", as GM claims.

    2. What is the best approach to determine the severity of this condition?

    3. What is the relative cost of a rebuild on a 5.7L V8 vs. a crate replacement engine? I'm not experienced in "big" overhauls such as this so I'm trying to weigh my options with keeping the truck or getting rid of it.

    I own a 2001 Silverado with 98K miles. 5.7L, Z71, LT, extended cab. The automatic transmission just died and I put in a Jasper rebuild two weeks ago. That came out of nowhere as I just returned from a long road trip and experienced no issues, literally, until I pulled into my driveway. So, there's the only silver lining I could find

    Other issues I'm frustrated with:

    I bought it certified pre-owned from the dealer. It was a lease return, one owner, 53K miles. Right after the warranty expired (3 months) all this crap began (see list). Keep in mind, this truck had a 270 point inspection to get CPO status, according to the dealer.

    - Dash lights started dropping like flies (55K miles)
    - Power mirrors quit working altogether (60K miles)
    - The gas gauge went haywire (57K miles - $700 sending unit repair – known GM issue, no recall or dealer fix)
    - Piston slap (www.pistonslap.com) (80K miles)
    - AC and/or heater core is failing (85K miles)
    - Transmission died (97K miles)

    Any inputs/advice/clarity is GREATLY appreciated.

    Thanks,
    Bow4elk

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    Re: Piston Slap!

    You have a 350 in a 2001? I thought those were used up and were just designated for full size Vans through the end of 2002. Either way, the 350's from mid 96 or so did have piston slap. However, in my experience it wasn't/isn't Near as bad as the LS based motors (4.8,5.3 and 6.0). We have a 6.0 at work that knocks (almost sounds like a rod going when really cold) really bad for 2-3 minutes. Once warm though, it's quiet as a mouse. I'd say it started knocking around 50-60k and it has about 140k on it now with no problems. You'd think the metal to metal contact like that would cause premature wear but I don't know. Some of our trucks have well over 300k on them (350's) and 1 of our 4.8's is pushing 300k. All of them have that annoying piston slap. None are as bad as our 6.0 I'm thinking of though. I guess it would depend on the motor/tolerances.. About the only way to tell would be to tear it apart. I've known several people swear off GM trucks because of the piston slap/knock. My understanding is they went to coated pistons somewhere around 05. However, I've heard 07's with the same knock? Hopefully this is taken care of by now... A 40k dollar truck shouldn't sound like a diesel unless it is one.

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    Re: Piston Slap!

    I didn't address your other issues.. Dashlights- I'm not sure about that. Power Mirror failures are common but easy to fix. Gas gauge (and fuel pump) failures are common. Heater core-hit and miss deal. I flush my system every 50k even though DexCool is suppose to go 150k. I don't trust that stuff.. The old formulation anyway. Tranny- hit and miss again. I know alot of guys have the transmissions go around 100k. Oddly enough, these are all 1500 Silverados. We have High mileage 2500/3500 Vans at work with the originals in them. I don't know if there's upgraded internals or what. Even a crate motor swap is pricey if you're not doing it yourself. If you aren't comfortable with some piston slap, I'd trade it off. And forget the decarbon thing a dealer will try to sell you on. It works for a few weeks and then your back to knocking again.

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    Re: Piston Slap!

    No, I was in brain fart mode...I have a 5.3L in my 2001. Sorry for the confusion

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    Re: Piston Slap!

    What the deal with the power mirrors? Easy fix? Bad switch? Some of this stuff seems reoccurring, which is why I ask. No sense in tracking down some mystery if it's a known issue, like the fuel gauge thing. I assume is a bad switch but honestly I haven't dug into it. I did replace the passenger door window regulator recently after the cable broke. I just bought an aftermarket unit on line and swapped it out in about 20 minutes. Works great.

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    Re: Piston Slap!

    I am curious about what all the folks over at piston slap are saying now that their trucks are still running strong despite the noise at start-up. I have yet to replace/rebuild a engine in the 10yrs since this issue emerged. Hmm..
    "Contrary to common belief, planning is complicated and is not run by complete idiots, so you'll just have to trust that the decisions were made on good information that's not made available to you."

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    Re: Piston Slap!

    That's more problems than the 10 GM vehicles I've owned combined. Sounds like that thing was in a flood to have that many things go bad.

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    Re: Piston Slap!

    I had an '02 Tahoe with the 5.3 and some piston slap - I was kinda po'd but traded it in with 100k and it still ran great despite the slight pinging sound in the morning.
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    Re: Piston Slap!

    On the mirrors, I just put new ones on. Did it on my Blazer and my Silverado. I know of 2 other blazers and another Silverado that needed new mirrors as well. This is why I assumed it was common. Every one I know with a Silverado has done the fuel pump/guage thing. I did my transmission around 120k. When I had mine done I was told the 2nd gear is weak from the factory on these trucks. On the piston slap, as noted above, most of these motors are getting high mileage out of them with no internal issues whatsoever. It's still not excusable but if tolerated, the motor will most likely be fine. I have heard of a few shattered pistons laying in the oil pans though. However, they are few and far between....

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    Re: Piston Slap!

    Quote Originally Posted by shadams View Post
    I am curious about what all the folks over at piston slap are saying now that their trucks are still running strong despite the noise at start-up. I have yet to replace/rebuild a engine in the 10yrs since this issue emerged. Hmm..
    But you and I have to both admit, that "Clacking" metal on metal on start up is a bad thing.

    To the 5.3L's rescue, The Piston's short skirt design. The force of the Piston"s Slap, never exceeds the Piston's Strength. But selling from a 300 unit/year dealership at the time, with 55-60% trucks, I did see 3 engines on the motor stand.

    My question is, If it is only a incovience, why did GM change many engines in 2001-2002 under warranty? Why do only certain cylinder's pistons have Teflon Wear Guards, as Factory Designs? Why did GM's first TSB state "Remove Motor and replace (i think it was ) 3 pistons?"
    And Why did Ford at the same time, Build thier engine with closer tolerences, and recommend 5W20 oil? I have yet to see all but 1 Ford engine on the stand. And that one went 57,000km's without an oil change.
    Last edited by doh; 09-30-2009 at 07:34 PM.

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    Re: Piston Slap!

    And GM wonders why their reputation died.

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    Re: Piston Slap!

    I have been told by the GM training center that aluminum expands almost twice as much as cast iron. So the pistons have to be made smaller so they fit properly when warmed up. My 3.4 V6 has done the same thing (another engine with this congenital problem) since about 15,000 miles and has caused no trouble, I have 148,000 on it now. If it only make the noise for a few minutes cold I would not be concerned, almost every one I see in the shop has this noise. In fact I don't even notice it because because I hear it so much, it is just how these sound. I think this has been present in earlier times but the blocks were significantly heavier then and that muffled the noises better than today. Couple that with how much quieter todays vehicles interiors are and you hear things that you did not before. At 98,000 miles I would just ignore it and drive it, most likely it will never cause you trouble.
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    Re: Piston Slap!

    Quote Originally Posted by dr.gizmo View Post
    I have been told by the GM training center that aluminum expands almost twice as much as cast iron. So the pistons have to be made smaller so they fit properly when warmed up. My 3.4 V6 has done the same thing (another engine with this congenital problem) since about 15,000 miles and has caused no trouble, I have 148,000 on it now. If it only make the noise for a few minutes cold I would not be concerned, almost every one I see in the shop has this noise. In fact I don't even notice it because because I hear it so much, it is just how these sound. I think this has been present in earlier times but the blocks were significantly heavier then and that muffled the noises better than today. Couple that with how much quieter todays vehicles interiors are and you hear things that you did not before. At 98,000 miles I would just ignore it and drive it, most likely it will never cause you trouble.
    I would ignore it also, don't get me wrong. The question is "Why am I dealing with it in the first place?"

    "My buddies 5.4L Ford doesn't do it, it's aluminum and cast?" "My girl friends Hemi doen't do it"

    Why does anyone have to have piston slap too worry about in the first place? In today's day and age?

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    Re: Piston Slap!

    And to "Rant about it"

    How can anyone say, that back in testing the "New and Improved SBC, (that has twice the life span of the "Last SBC") in 97-98, No one went out one morning, eating his jelly doughnut, and fired one of these up that had 20-60K miles, and said, "Hey wait, what's that noise?"

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    Re: Piston Slap!

    NIH, Not Invented Here.
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