GM Piston Slap

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Well, good luck.

I purchased new a 2000 GMC Sierra with that Vortec 5.3. After about a year it started the piston slap thing.

In my case, Mobil 1 15W-50 in summer made the motor silent. There was no MPG penalty I could detect.

However, winters here can dip to -40 or a bit colder. So I ran Mobil 1 0W-30 in winter and the thing knocked a bit cold and gave off an anoying ticking sound hot.

I traded it for a new Toyota Prius and the new car is almost silent, even when the motor runs. My 1984 Ford F-150 with 302 V8 is quieter than the GMC motor ever was.
 
Craig, the "assembly lube" used after replacing the pistons and bearing assemblies!
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I haven't found any specific lube that works in all the oil analysis customers we have complaining of that noise.

Be careful using Viscosity to deaden sound as you can sacrifice lubricity and thats worse. As long as the oil analysis signature and operation is satisfactory I say accept it and enjoy the very efficient engine.
 
So far I'm looking at it this way. Since it has been brought to light, I have not seen much in the way of any problems the piston slap has caused other than an annoying sound. Some on other forums have it and have well over 150k with no problems. I seem to have it now and then. Weird how it comes and goes in my 02 Silverado with the 5.3. I'm currently running Series 3k 5w-30 AMSOIL The last analysis was at 12k on the oil and Terry said it looked good and continued use was ok. So I am. Terry is the man!
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My understanding is that RedLine 10W-30 improved it. This was discusssed a while back-like a year or so. I can tell you that Mobil 1 10W-30 doesn't help.
 
I had a 1996 Chevy S-10 2.2 OHV that had a slight piston slap and different weight oil didn't make it go away, so I just went back to 10W-30. Noise went away completely once engine warmed up.
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I'm glad this topic was revisited. I now have evidence to show my wife, proving I'm not an obscene, juvenile, pervert. Every time I talk about piston slap and rod knock she accuses me of making it up, just to be gross.

Now will you please help me convince her that a loose exhaust system is not muff rub!
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Try a good moly based oil
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I had some piston slap and switched over to MC 5w30 with a shot of Valvoline syn oil treatment.

I calculate I am aroudn 400-500ppm MOLY, whhihc is like redline oil.

If you wanan play mixoligst. You could mix some Penzzoil and a quart of redline.
 
The guys at the local engine rebuilding/maching shop are emphatic on the use of synthetic oil in the 3100's from when they are brand new. Their theory is that the engines really aren't very suited to northern climates, and that cold startups are seriously bad for them, causing the development of the piston slap problem.

They also claim that exclusively southern or summer operated engines don't suffer, or only minimally suffer from the problem at all. Any truth to this?

edit: I thought I'd just add, normally these guys aren't very big on synthetic at all -- 'a waste of money', and they're all 'religous' 3000 mile oil changers.
 
i am going to put on my flame suite and tell you what works for me. castrol syntec 10w30. i know it is not the best oil in the world, but it sure makes my wifes 5.3 tahoe quiet in the mornigs. ALSO, use chevron techtron in the fuel tank every 1k or so. MOBIL 1 IN ALL WEIGHTS AND MIXES MAKES THESE ENGINES NOISEY. i have also had the best resaults with the cheap purolater filters. the 3.99 ones. -ed.
 
There are two separate causes for the noise GM calls CSK (cold start knock).

One is the piston rattling around in the bore.

The other is carbon built up on the top of the piston and on the head. A warm engine expands enough so the piston and combustion chamber don't knock their carbon together, but a cold engine might have contact. A very good combustion chamber cleaner helps.
http://www.pistonslap.com/tsb/010601028A.htm


Ken
 
And that the idea of getting some moly in the mix. Its a nice additive that will stick to the piston and helps it stay lubed for a cold start.


I am not surprised syntec works. I remember a article that they have an additive in it that helps build a film on the metal surfaces.
 
quote:

Originally posted by eddyzima:
i am going to put on my flame suite and tell you what works for me. castrol syntec 10w30. i know it is not the best oil in the world, but it sure makes my wifes 5.3 tahoe quiet in the mornigs. ALSO, use chevron techtron in the fuel tank every 1k or so. MOBIL 1 IN ALL WEIGHTS AND MIXES MAKES THESE ENGINES NOISEY. i have also had the best resaults with the cheap purolater filters. the 3.99 ones. -ed.

Leave your flame suit in the closet. You've made a precise statement about what works for you. You have not, by way of contrast, claimed or suggested that therefore Syntec 10w-30 is the best thing invented for all cars, cures cancer, prevents nuclear war, etc. . . It's your car and your money and if you've found a way to quiet this befuddling problem in your car, power to you, regardless of whether your solution is Syntec, Redline, or Crisco!
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