Anybody else own a GM-Chevy 6.0L "knocker"

[hillbilly]

Just wanted to know what others thought about this situation. My truck is a '02 GMC Sierra 1500HD crew cab, I love everything but that tapping,knocking engine. Sometimes sounds like a diesel.

I guess my real question is what is everyone's thought on how it will effect engine life. Sorry if this has been beat to death already. I'm using Amsoil 5W-30 right now, gonna do Auto-Rx with YB next. It's almost embarrassing to start up a nice truck in front of others making all that racket.

 

[zulu]

GM is well aware of the "piston slap" issues that causes all the commotion on cold starts. Their stance is that if it goes away once at operating temp, it's "normal." I've got a 5.3 in my 1500 and it isn't as bad as you describe, but definately a noisy one on cold mornings. I had best luck using a thicker oil (GC 0W-30) to minimize the ticking, but still didn't totally go away. I'm tempted to try a 40W once the winter is over.

FWIW, I've seen plenty of 5.3/6.0 engines that sounded like a bucket of marbles but still had 200K +. I don't think durability is much of an issue. Just be gentle with the throttle until the engine warms up to temp.

 

[artificialist]

Has it gotten worse recently? How many miles do you have? The timing chain and guide may have reached the end of its life.

 

[NHHEMI]

In addition to the infamous Piston Slap issue around that time frame for GM they also had trouble with carbon build up on to of the pistons leading to knocking. The Piston Slap goes away once the engine warms up. The carbon issue is also something that is more noticeable at cold start but can continue to make noise once the engine warms up.

Supposedly, according to GM who came up with the carbon build up issue in response to everyone claiming Piston Slap, the carbon builds up so bad on the top/dome of the piston it actually raises compression and causes detonation with low octane fuel. In theory I can see this as possible and some have reported that the noise went away( completely or vastly reduced )after using a Top End Cleaner sold by GM.

The TEC is supposed to remove the carbon build up. It gets applied and then you have to let it sit to let it eat away at the carbon as I recall. You do not have to tear the engine down or anything to use it. I recall having read letting it sit overnight gives the best results. Follow directions on bottle for proper application.

Just another option to consider. Probably PS but that can't be solved without a rebuild. Wouldn't hurt to try a bottle of the TEC. All you would be out is a little time and the cost of a bottle.

 

[mrsilv04]

Try a run of a 10w-30 synthetic. Dad's Sierra has a little slap, the 10w-30 quieted it down nicely.

It's worth a try.

 

[JDR15467]

I just switched from M1 EP to Havoline conventional on my 99 suburban with 5.7l, 106k. It was only 35 out today, and it sounded terrible for the 1st 15 to 20 seconds. Why would one oil cause this more than another, or does the change require time to adjust? M1 seemed to have stopped/reduced the noise when I used to have it using valvoline conventional during very cold starts.

 

[Ken2]

As NHHEMI says, that knocking noise was sometimes carbon on the piston crown harmless hitting the head. No harm done until you try to sell the truck.... The knock sensor won't allow detonation unless the carbon glows red and ignites the fuel before the spark plug fires.

Do try the carbon cleaning, and maybe more than one dose to get it all.

Try different brands of oil. Some brands damp noises better than others. You might try the so-called oils for high mileage engines and see if those damp the knocking better than others.

 

[Rlc2500HD]

My 2001 2500HD has the knock and 160,000 miles. I dont really notice it unless I remote start. Goes away with in seconds.

 

[ThirdeYe]

We have a GM 3.1 with the famous piston slap, I've tried all sorts of brands, synthetic, synthetic blend, conventional, 5W-30 and 10W-30, nothing really made a difference. It's still going now at over 75,000 miles though.

 

[NHHEMI]

Originally Posted By: JDR15467
I just switched from M1 EP to Havoline conventional on my 99 suburban with 5.7l, 106k. It was only 35 out today, and it sounded terrible for the 1st 15 to 20 seconds. Why would one oil cause this more than another, or does the change require time to adjust? M1 seemed to have stopped/reduced the noise when I used to have it using valvoline conventional during very cold starts.


You went from a synthetic oil to a conventional oil is what the problem is. Conventional oil drains off the metal surfaces when it sits whereas synthetic leaves a film. Plus synthetic retains it's viscosity to a lower temp and flows much easier at cold temps than conventional oil does. 35 isn't really 'cold" but it is cold enough. I would wager if you went back to the M1 or some other synthetic your issue would go away or lessen considerably.

Just read what you wrote... Engine makes noise at cold start with Valvoline and Havoline conventional oils but does not with M1 EP which is a synthetic. That is your answer right there.

 

[NHHEMI]

Originally Posted By: Ken2
As NHHEMI says, that knocking noise was sometimes carbon on the piston crown harmless hitting the head. No harm done until you try to sell the truck.... The knock sensor won't allow detonation unless the carbon glows red and ignites the fuel before the spark plug fires.

Do try the carbon cleaning, and maybe more than one dose to get it all.

Try different brands of oil. Some brands damp noises better than others. You might try the so-called oils for high mileage engines and see if those damp the knocking better than others.


You can still get some detonation if the carbon build up is severe enough to raise the compression high enough. Read that in a GM TSB. I agree with your comment on the knock sensor. It "should" retard timing enough to stop it but I guess it can still happen on severe cases.

 

[Propflux01]

Originally Posted By: NHHEMI

You went from a synthetic oil to a conventional oil is what the problem is. Conventional oil drains off the metal surfaces when it sits whereas synthetic leaves a film. Plus synthetic retains it's viscosity to a lower temp and flows much easier at cold temps than conventional oil does. 35 isn't really 'cold" but it is cold enough.


Huh????

 

[CrAlt]

Originally Posted By: NHHEMI
It "should" retard timing enough to stop it but I guess it can still happen on severe cases.

Which is a bummer because if the knock sensor hears one or 2 cyls knocking then it will retard the timing to all the cyls until it doesn't hear it anymore. You end up giving up performance because of this.

 

[artificialist]

Originally Posted By: CrAlt
Originally Posted By: NHHEMI
It "should" retard timing enough to stop it but I guess it can still happen on severe cases.

Which is a bummer because if the knock sensor hears one or 2 cyls knocking then it will retard the timing to all the cyls until it doesn't hear it anymore. You end up giving up performance because of this.


It always does on distributor and waste spark engines. However, some engines that have 1 coil per cylinder can adjust timing cylinder by cylinder. I'm not sure if the 6.0 can do this, but I know it is a 1 coil per cylinder engine.

 

[NHHEMI]

Originally Posted By: Tim H.
Originally Posted By: NHHEMI

You went from a synthetic oil to a conventional oil is what the problem is. Conventional oil drains off the metal surfaces when it sits whereas synthetic leaves a film. Plus synthetic retains it's viscosity to a lower temp and flows much easier at cold temps than conventional oil does. 35 isn't really 'cold" but it is cold enough.


Huh????


What do you mean HUH? Huh back at you.

 

[hillbilly]

The truck has 65,000 miles on it. The ticking does go away after startup sometimes, then comes back after its warm. Tick,tick,tick.

 

[StevieC]

I had this problem, not with this engine... Switching oil brands worked for me. Engines can be fussy... Just my 2 cents...

 

[JetStar]

Isn't the knock sensor going to retard the timimng regardless of the cause (piston slap or detonation)? I need to check to see if the knock sensor is active during warm-up or if it only becomes active after op temp is reached, or maybe closed loop?
I had a '96 GMC 1500 that I bought new that had this issue. Seems like it started at around 20K miles. It had 150K on it when I got rid of it. No engine work ever done on it. I always used M1 10W30 synthetic in it. Wish I could say the fuel pump was as reliable.

 

[NHHEMI]

Originally Posted By: JetStar
Isn't the knock sensor going to retard the timimng regardless of the cause (piston slap or detonation)? I need to check to see if the knock sensor is active during warm-up or if it only becomes active after op temp is reached, or maybe closed loop?
I had a '96 GMC 1500 that I bought new that had this issue. Seems like it started at around 20K miles. It had 150K on it when I got rid of it. No engine work ever done on it. I always used M1 10W30 synthetic in it. Wish I could say the fuel pump was as reliable.


The piston slap issue has nothing to do with the Knock Sensor. There is too much play, with the engine cold, between the piston and the cylinder sleeve. Once the engine warms up, and things expand, the slop is gone and so is the noise.

 

[NHHEMI]

Originally Posted By: StevieC
I had this problem, not with this engine... Switching oil brands worked for me. Engines can be fussy... Just my 2 cents...


I have seen engines respond different to different oils as well. Also seen engine noise as a result of the oil filter used on some vehicles. Change the oil or oil filter and noise goes away or lessens considerably.