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Valve Chatter???


SM 2003
Full Member
Apr 29, 2002
Birmingham, Alabama
In the mornings, my 8.1L has what sounds to be valve chatter for the first 15 seconds, after which, it goes away. From working on older vehicles, I would guess that it the culprit is the lifters not pumping up immediately upon startup. When I start the engine, I have great oil pressure though. Is anyone else hearing this? Is this a potential problem? It only does this after sitting for several hours.
I have the same thing but I have the 5.3L when I start it sounds like it is running ruff but after runing a little bit it stops.
It sounds like the anti drain back valve in your oil filter
is not working properly.
weco, Why would the drainback valve matter since the fiter is in an inverted,vertical postion where oil can't drain out?
Why does the filter have an anti-drainback valve?
Could the noise be the dreaded piston slap? :cautious:
I have the same problem, I talked to the dealer and they told me that the problem is when the vehical is cold the pistons will make some noise for about 15 seconds. Does not hurt the vehical. They told me if the sound does not go away bring it in right away. may be due to the time it take for the pistons to heat up.
I have the 8.1 and mine does the same thing. A friend has the 8.1 also and it's the same. I have not seen this as a problem. Let us know if you find anything different.

So I have done a search on other forums and it seems that GM says this piston slap is not a problem. They say piston slap occurs when the engine is cold and there is excessive tolarances betwen the piston and piston wall. GM also says that this is not detrimental to the life of the engine. Is that so? Ok, I can conceive that special metals expand differently at different temperatures, but it would seem that if that there is enough space between piston and bore to cause a noise, something bad must be happening. Is this something I need to bring in to have checked?
I had a '99 Sierra Z71 3 door and my wife had a shortbed Z71. Both trucks had the 5.3. Hers had 66,000 miles when we traded it and mine had 43,000. Both trucks made the noise from the time they were new and it never got any louder. I have been told and also read that this noise may not be piston slap, but may in fact be the fuel injectors. I tend to believe it may be just that.
Yep, my 8.1 AV does it also. Sounds a little more like valves to me as it does'nt sound very deep in the engine and is kinda clicky. I was hoping it was one of those breaking in things since it goes away after 5 min but I guess not. ???

When it was new, I had some fan belt squeel at warm up but no longer.
I have a 5.3 which starts smooth and quiet every time. Is it particularly cold where you guys are at? I'm wondering if this is something I can expect as the weather changes in this part of the country later in the year.
My 5.3 does it BIG TIME especially underload. I found this out for sure after I drove it from FL -> OK and back last week. Chatter, chatter, chatter. I'm not sure if it is valves or fuel injectors ... leaning toward the injectors.
No, it's not cold in Atlanta. And it is not a deep knock, sounds more like lifters, and only lasts a few seconds. I don't know what the piston slap sounds like, so I cannot be sure without getting under the hood with a stethescope to determine where it is originating. I haven't heard of the injectors making noise. Is that a common thing on initial start-up?
Morning All,
My 2002 Avalanche has 2775 miles on it. The 8.1 L engine has always made a diesel noise upon startup. This noise has always ceased after about 20 seconds. It's just one of those GM characteristics I guess. It's going to Mobil1 5w30 at 3K miles.
I have used synthetic in my 8.1 the noise will not go away. I still have it on start up for the first 20 seconds or so. It seems to be a common thing with the 8.1.