Rod or piston slap

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How can I tell , I have a 96 lx450 , it is only present at low rpm ... a very faint sound like a wrist pin or piston slap .
What should I do to extend the life out of it ...it only has 115, 000 it's very clean and has allways had the proper maintance.
Thanks
Greg
 
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If your truck has had proper maintenance, I don't think you should be experiencing rod knock or piston slap this early in the game. Maybe it's something else. An accessory on it's way out maybe.
 
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I had piston slap in my second 1FZ-FE after it ran hot for a few months. Dealer warrantied it and dropped in a new long block.

Do you hear it whether it's in Park and N or only in 1,2,D with a slight load?
 
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re: noise

Temps fine , compression is good , no oil consumpshion . the noise is more noticeable in park ... it's when you just touch the pedal and come above idle ...just burp it and you hear what I am thinking is the slap or the knock ... over 700 rpms you can't even hear it and if I was not a retired wench and knew nothing about cars I would not know it was there .
Since it is there , I am going to treat it , I put amsoil , but I will increase the viscosity ...I do have the early cold day rattle when I first start it up .
Thanks
Greg
 
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i bet you're hearing slight pinging.
right off idle just for a half sec. as you lightly tap the throttle... has been talked about a lot here. very much doubt it's slap, though the sound is a rattley thing...i have it.
 
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Gregory Hysock said:
Yes thats where I hear it right off idle ...
Thanks
Greg

Greg,
Robbie ran his first '93 for ~60k miles with a slight piston slap. In his case the engine overheated after the PHH failed at highway speeds. Maybe you can try some 15-50 M1 for a few months and see if it gets any worse.

Check with Robbie (powderpig).
-B-
 
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Romer

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Could it be Carbon build up in your ring packs??????

I was surprised how much carbon there was on top of the pistons and in the ring packs when Robbie did my head gasket. w/o doing a full rebuild, he was not able to do anything with the ring packs and noticed some scratches the ring packs were making.

I currently am trying a product caled AutoRx talked about on bobistheoilguy.com to attack the carbon in the ring packs.

This may not be your problem, but who knows! Hopefully Robbie will chime in here.

Ken
 

powderpig

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I have not seen any wrist pin problems in these engines yet. I have seen Piston slap on trucks with these miles. Mostly like Kens truck that was maintained poorly or was over heated(not to say your truck has this). Another problem that can lead to piston slap is injector fouling that creates a lean condition. If you feel that you know what piston slap is(sounds like you do), then I would bet that you have it for what ever reason.
You say compression was good, what was the numbers.?
Any how with good oil you can control it for a long time until you get tired of the sound. Warm up is real important, before you work it hard.
It might worth your time to look at it with a bore scope or find the cylinder that is the problem. Or do the PM on the HG and take a look. later robbie
 

Romer

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powderpig said:
Mostly like Kens truck that was maintained poorly or was over heated

Just to be clear . . . . He means poorly maintained by the PO. After all, I took it to Robbie, how could it be poorly maintained now. Unless of course Robbie is telling me he did the job poorly, No . . . . maybe he means . . . Aw screw it, the PO poorly maintained it. Remember I had to replace my Tcase last year most likely because he let it run dry at some point.
 
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Do the wooden dowel trick on each component with someone in the driver's seat repeatedly doing whatever needs to be done to make the noise. My 93 has a spot somewhere near 1500 in neutral/park that it will make a rattly noise. This noise band is only a couple hundred RPM wide. I first noticed it when I was bored and waiting for my wife somewhere around 40,000 miles. I gently revved it in tiny increments for whatever reason and suddenly heard this racket. It has not changed a whit in the ensuing 115,000 miles including serious heavy towing, etc.

I always attributed it to either THE rpm at which the mass of the unloaded pistons would maximize the bang of whatever slack they had in the piston/wrist pin junction, or THE rpm at which the timing chain would ride up the timing gear teeth and come down in that continuous crackle/rattle. It won't do it in gear (loaded).

Either way, as I say there has been no change, so I attribute it to just the geometry and physics of a truck engine with heavy parts. Now that you mention it, I wonder if the engine still does it now that I've had the head/timing gear off?

I'm checking my watch to see how long it takes everyone else to find this little narrow RPM range. I've never done it on the 97 but will next time I drive it....

Anyhow, I'd play with oil viscosities and consider some cylinder cleaning strategy such as Redline or Techron in the interim. But I definitely would not ascribe this to an internal engine problem unless other signs of prior abuse exist.

DougM
 
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just to speak of some other posibilities, the bearing in the alt belt idler pulley/roller often fails and can make a good bit of noise that kind of sounds like a faint knock, though with a more random tempo, you can run without this pulley for the pourpose of checking this sound, waterpumps and other accesories can make noises also but not quite like that.


oh and is this a one time knock when coming off of idle? the PCV vale tapps then the manifold pressure increases, you can recreate this by quickly squeezing the PVC hose shut. (harder to do with older hardened hoses)
 
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RavenTai said:
... the PCV valve taps when the manifold pressure increases, you can recreate this by quickly squeezing the PVC hose shut.

I had the bonnet open with the engine idling for about 30 minutes a few weeks ago. You can clearly hear the PCV opening and closing every few seconds. I hadn't noticed it before and it took a minute or two to figure out where the noise was coming from.

-B-
 

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