Recently, my 99 GMC Z71 with a 5.3L Vortec started making tappet noises for about the first 30 seconds of a cold start-up (doesn't do it when its warm) , it never did it before, I hate engine noise!!, is this leading to something more serious? do these engines have a habit of doing this?
I change my oil faithfully every 4000 miles and the truck only has 59,000 KMS on it
A buddy of mine told me to switch to synthetic oil cause it coats the components better especially at start-up, the tappet noise would probably go away
Not in a 99' engine buddy! If he dumps 10W40 in there he'll have piston slap AND valve chatter on startup. If the manufacturer says 5W30 all year, use 5W30 all year.
Same thing with my "99 Z71, 5.3 , 75,000 miles, light tapping on start-up. I changed to Mobil 1 Synthetic 5W30 last year and haven't noticed any change. Tapping only last for a few seconds.??
Piston slap has nothing to do with oil type or weight, it has everything to do with piston-to-bore clearances. I recommend synthetic oils to anyone and everyone, so I think you should still do that, but don't expect a change in yer' noisy startup. Also, it will get worse in the winter! The colder the block is in startup the louder it gets.
You may be right Doc, but the guy who rebuilt my 88 told me they're full of shit. Not saying that he's not too, but he was a very well respected engine rebuilder here for years, and thats saying alot, around here. He's 64 now, a little arrogant, and maybe with some memory lapse, but around here, when all someone has to say about you is good, you tend to take their word for it. Till you get screwed that is. He worked for mopar dealer when he started. They encouraged him NOT to change the oil if it looked anything but black, charge the customer for oil change and filter, and send them on their merry way. Thats why he became the famous, independent drag racer he is on his own merit. Then again, just this morning, I was telling a fellow worker, an ex-mechanic about my truck troubles and he said, he didn't work for GM anymore because he wouldn't NOT change a particular part like they told him to, but charged the customer $450.00 anyway. You can ask a hundred other wrenches that work at Car X now, they've all got similar stories. I'm not hear to argue, I just state my experience. Somebody don't like it, I just wonder why. You know what I mean?
This data sheet may be helpful to understanding this issue. Info - Engine Knock on Cold Start #01-06-01-028 Engine Knock on Cold Start
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models
2002 Cadillac Escalade (2WD)
with 4.8L, 5.3L or 6.0L Engine (VINs V, T, U -- RPOs LR4, LM7, LQ4)
Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.
This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.
Important At this time, attempts to repair this condition by replacing the engine assembly or pistons is not recommended.
Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise your Area Service Manager.
Key word, "noise." Of course the noise doesn't but you aren't going to tell me that the mechanical effect doesn't.
And why is that?
he he, that will calm about 2/3rds of them, at least while they are in front of the service manager, [who don't know what he's doing either, in my experience]. Thats all I can speak for, my experience.
One thing sythetic oil did for me was reveal all the problems my engine had. More than six mechanics could do.
Yes, I can tell you from personal experience with many different engines down through the years that have "piston slap".....most of them don't have any mechanical effect on the engine.
Because the condition would re-appear in time. It's a all a part of the design.
The data sheet says "some" so I guess some weren't part of the design. I just don't buy what the data sheet claims. I'd guess those engines and/or components were either machined carelessly, and/or inspected carelessly, then put in the rig for rush sale.
They have done long term studies using oil analysis and completing part analysis after scheduled tear downs and have not found any related accelerated wear issues. If piston slap caused premature wear you would start seeing elevated PPM's of iron in your used oil sample. Hasn't been a problem. I have been told that the piston skirts they are using on these engines are much shorter (with overall weight reduction as the goal) and that this is a related cause. The GM Dealers around here actually service these offending engines with a BG fuel injector cleaning treatment. It seems to work but of course is just a band aid.
Thanks, for all I know about the exact problem, which is very little, I do know pistons have skirts on them for a good reason and I think weight would be a very bad reason to eliminate them. You'd see iron for iron cylinder bores, but aluminum for most pistons. If GM is using its own 20 dollar per bottle injector cleaner, they'd better not use more than one of this caustic substance, as they warn on the bottle. Hell, maybe thats the crap that damaged my own engine. It never cleaned my injectors, at least not to restore them as new, I had to get new ones and that solved that problem. Not one mechanic suggested this however. And I don't know why, because they were cheap. Most all anyone does these days is band aid I guess. Very expensive band aids I might add.
No, I haven't, but I knew that someone would probably one day prove that four stroke motocross was the way to go, even if they are slow as hell and have to stretch the track to make up for it. We learn all the time don't we? You see, when you talk about motorcycles, and motorcycle racing, I can keep up with you, but this is not a motorcycle group, so I've got little else to say.
As far as the Avalanche goes, in my area anyway, it didnt' take long for them to get a bad rap. And anyone who would buy a test vehicle, better have money up the ying yang cause they deserve it. Now, wanna do some more testing?
Well DJ, they are not slow as hell, in fact in the 125 class the TwoSmoke is going to the wayside due to the strength of the four strokers, as far as the avalanche, it has been out for a few years and as you may be aware most vehicles go throught the test period, some come out with flying colours others don't. Of all the GMC vehicles I have owned this is definately the nicest one I have owned and so far has been flawless and I hope it keeps this way. Take a look at the posts in this news group, there are many off topic, so a simple comment about a four stroke piston skirt I don't think is out of line, just a simple comment.
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