Recalls & Engine Knock Info

[Toadz]

I wish I got that letter. I hate that engine knock. It's going to be impossible to sell the truck to anyone who doesn't know anything about these engines.

[CALI-OFFROADER]

wow, very interesting. I always just let it warm up for about one minute then the knock just goes away. This only happens on my 97 Z71 5.7 vortec, and 2000 corvette 5.7, but not on my 03 2500HD 6.0L vortec. I thought this was normal. A new engine never hurts though:)

[4DOORVETT]

Just found this thread by chance and we can call this my introduction to FSC. We own a 2000 Suburban LT 5.3, stock. It also has the "piston slap". I can't seem to locate my PCV valve either, did a search and this is where I ended up.

[zstehlar58]

Hey guys ... is anyone else experiencing this problem as well?? I have a 2001 Chevy Silverado 2500 HD extended cab 4x4 with the V8.. well for about a year now when it rains my truck does not want to start up... and sometimes ill be driving down the road and the check engine light comes on and ive got about 30 seconds to pull over be4 my truck dies but if you wait 15 mins it will fire back up.... ive replaced the starter, the alternator, the fuel pump and all the lines, changed the plugs and even bought a new battery... now there's no distributor cap on my truck does anyone think it could be the ignition coil?? im running out of ideas and no mechanic can seem to find anything wrong with it... something is getting damp or wet i just dont know what.. Please help...

[Toadz]

Hey guys ... is anyone else experiencing this problem as well?? I have a 2001 Chevy Silverado 2500 HD extended cab 4x4 with the V8.. well for about a year now when it rains my truck does not want to start up... and sometimes ill be driving down the road and the check engine light comes on and ive got about 30 seconds to pull over be4 my truck dies but if you wait 15 mins it will fire back up.... ive replaced the starter, the alternator, the fuel pump and all the lines, changed the plugs and even bought a new battery... now there's no distributor cap on my truck does anyone think it could be the ignition coil?? im running out of ideas and no mechanic can seem to find anything wrong with it... something is getting damp or wet i just dont know what.. Please help...

Sorry but you should really make a new thread for this. Recalls and Engine Knock info doesn't really cover what you're looking for. My only bit of help would be to get your codes scanned. Many parts stores will do it for free.

[Jamesd]

I have an 01 HD with the 6.0. I read majority of this thread but I did not find an answer. I too have the rod knock sound at idle only. It is a little louder when it is cold but when it warms up it is still there. As soon as you bring it off idle say around 1,000 rpm's, it goes away. So my question is that if my rod knock noise happens all the time, is this still part of the piston slap problem or do I actually have a rod bearing going? It has 143k on the clock and no it does not ping, have any exhaust leaks or lifter chatter.

Thanks, James

[TJbear5300]

Hello all. I recently aquired a 2000 GMC Sierra with the 5.3 and it also has the piston slap/knock. I was aware of this issue beforehand but in my research I found it supposedly doesn't cause any reliability problems. But I can definetly understand the frustration of people who bought them new or slightly used. I would have been livid in that case, lol.

Seems like some mornings (same outside temp), it doesn't knock at all, while others, it sounds like crap. But most of the time, it will knock/clatter to some extent. If I start it cold and just let it idle, it will keep making some racket as long as I let it idle until it is FULLY warmed up. But If I let it run for a minute and then drive away, it dissapears. Like an earlier poster mentioned, it seems to need a "load" on it to go away. After that, it is smooth and quiet, not one tick or knock sound.

Friend insists it's rod knock but that would only get worse as the engine warms as far as I know.

I'm running Valvoline Full Synthetic 5w30 and an AC filter. I may try some seafoam or even GM top engine cleaner at some point but tricks like that never seem to work for me. Kinda sucks that replacing the engine with a new one will result in the same BS.

BTW, I don't see how octane could have any effect on this piston slap thing. At idle with the engine cold, octane will make little difference aside from it possibly starting a little harder with the high octane in cold temps (if the vehicle calls for 87).

[mntahoe]

I have an 01 HD with the 6.0. I read majority of this thread but I did not find an answer. I too have the rod knock sound at idle only. It is a little louder when it is cold but when it warms up it is still there. As soon as you bring it off idle say around 1,000 rpm's, it goes away. So my question is that if my rod knock noise happens all the time, is this still part of the piston slap problem or do I actually have a rod bearing going? It has 143k on the clock and no it does not ping, have any exhaust leaks or lifter chatter.

Thanks, James

It's difficult to describe these things, but here's my best shot. Piston slap is softer, more like a bad lifter, but not quite.
A rod knock is deeper and more "solid" sounding. It doesn't usually go away, but rather gets louder with increased rpm. It's also frequently accompanied by low oil pressure.
Sounds like the piston problem to me, though with that many miles you might want to check your belt tensioner as well. They can raise a pretty good ruckus when they fail too.

[flynbrian]

Seafoam, administered through a vacumn line into the intake will decarbon the valves as well as the pistons and you dont have to take anything apart. And once a major cleaning has been done at the engine just add it to your fuel from time to time and it will reduce and get rid of carbon.

Just the good old red & white metal can you see on the shelf at the auto parts store. Yes it will stink and smoke like somethings on fire. But it works. I used it on several of my old cars motorcycles and pick-ups. It really does a nice job.

Due to the converters and electronics it may be better to run the seafoam additive through the tank, instead of right into the engine. But its most effective when dumped right in through a vacumn hose. Look it up on You-Tube. There is video of people using Seafoam on newer injected cars & trucks.

I work for Valco, Not at all affiliated with Seafoam, So this is my honest opinion not a sales pitch.

[Rampage2]

Hello all. I recently aquired a 2000 GMC Sierra with the 5.3 and it also has the piston slap/knock. I was aware of this issue beforehand but in my research I found it supposedly doesn't cause any reliability problems. But I can definetly understand the frustration of people who bought them new or slightly used. I would have been livid in that case, lol.

Seems like some mornings (same outside temp), it doesn't knock at all, while others, it sounds like crap. But most of the time, it will knock/clatter to some extent. If I start it cold and just let it idle, it will keep making some racket as long as I let it idle until it is FULLY warmed up. But If I let it run for a minute and then drive away, it dissapears. Like an earlier poster mentioned, it seems to need a "load" on it to go away. After that, it is smooth and quiet, not one tick or knock sound.

Friend insists it's rod knock but that would only get worse as the engine warms as far as I know.

I'm running Valvoline Full Synthetic 5w30 and an AC filter. I may try some seafoam or even GM top engine cleaner at some point but tricks like that never seem to work for me. Kinda sucks that replacing the engine with a new one will result in the same BS.

BTW, I don't see how octane could have any effect on this piston slap thing. At idle with the engine cold, octane will make little difference aside from it possibly starting a little harder with the high octane in cold temps (if the vehicle calls for 87).

TJbear5300,You motor noise description is pretty well spot on the same as mine.Have you tried the seafoam or top end cleaner yet?

[TJbear5300]

Haven't tried that stuff yet. Will do it just before I change the spark plugs.

[Toadz]

http://www.gm-trucks.com/forums/inde...pic=105143&hl=

Here's a discussion over at GMTrucks.com. Seems everyone there is 100% convinced it's normal and we should all shut up about it.

[PeterKesel]

Nice stuff yet.I really need more information about it.Thanks..

HID Light

[Toadz]

Nice stuff yet.I really need more information about it.Thanks..

HID Light

What more do you need to know about it? Do a Google search for it, there's tons of information about it as it's a well known problem for many manufacturers. There are fixes to it but most companies prefer to ignore it to avoid extra cost.

[The817Kid]

So this seems like a slightly dead topic, but I do have a question. When I purchased my 05 1500 Z71, it had a check engine light on. The CEL code came back with knock sensor. Well I started hearing the "engine knock". So I just figured the two were connected. I don't want to go to the trouble of changing these sensors since they are under the intake if it won't change anything. Any ideas on this?

[TJbear5300]

So this seems like a slightly dead topic, but I do have a question. When I purchased my 05 1500 Z71, it had a check engine light on. The CEL code came back with knock sensor. Well I started hearing the "engine knock". So I just figured the two were connected. I don't want to go to the trouble of changing these sensors since they are under the intake if it won't change anything. Any ideas on this?

When does it knock? After a cold start? When warmed up and accelerating? There are various sources of "knocks" with various reasons for them.

In other news, I finally did the seafoam thing. Didn't do a thing for the cold start piston slap but I didn't really have much hope for that anyways.

FYI, I also switched to Valvoline Maxlife semi-synthetic and it actually made the piston slap much worse. So I switched back to the Valvoline full synthetic and its back to "normal": light knock starting several seconds after cold start, lasting for 30 secs or so. Runs great otherwise.

[The817Kid]

It knocks after warm up. It is most noticable while at idle. The knocks increase with rpm's. It seems to stop once I start driving, or atleast I am unable to hear it while driving.

[TJbear5300]

It knocks after warm up. It is most noticable while at idle. The knocks increase with rpm's. It seems to stop once I start driving, or atleast I am unable to hear it while driving.

Hmm, doesn't sound like the usual piston slap "knocking" sound. Not sure this would be related to the knock sensor either.

[The817Kid]

Ok, well I'm going to replace the knock sensors Monday. I will let yall know what comes of it.

[The817Kid]

Well I got the new knock sensors put in. The check engine light hasn't come back on and the knock seems to be gone. I forgot to add that the engine is at 130k miles. So I suppose this was a different knock than the problem most are having.