CarolinaCamaro

A friends 2002 z28 is making some unwelcomed noises. He just got the car for a good price with what the previous owner said is piston slap/ possibly knock. Right now we are looking at what to look at to eliminate the sound or locate the problem.

The noise sounds like a dull knock or tapping and gets louder with more revs. I don't remember offhand if it goes away totally after awhile but I don't believe it does. It may get quieter though I have to check with him. The motor only has 80,000 miles and is an automatic with an unmodified rev limiter, pcm, and engine. I suppose it is possible it spun a bearing but he is hoping praying it is a loose bolt(s) on the flywheel as the sound is coming from the bottom of the engine at the back.

How easy is it to check the bolts on the flywheel? can it be done with ramps? What are the torque specs for the bolts?

Also any input or suggestions on what to look for would be helpful. I will talk with him tomorrow if more info is needed. I should just make him get his own acct here lol.

vsocks1

iTrader: (6)

Piston slap is usually when cold. If it happens all the time I would suspect rod knock.

'02 WS6

iTrader: (73)

Piston slap most commonly goes away after the motor is warmed up and in closed loop, but I've heard some that still have a faint slapping sound continuously.

5.3LJimmy

iTrader: (10)

Piston slap is generally only heard on cold starts and will go away after the engine is warmed up. Drain the oil and cut open the oil filter to look for metal shavings. If the oil is clean you can move on to the flexplate or other possibilities. The bellhousing is all one piece, which requires removal of the tranny to inspect the flexplate.

Man I type slow, I got double beat to the punch.

CarolinaCamaro

Yeah will def tell him to check that. Owner said car had regular oil changes and had receipts for the past 6 3k oil changes. said he never abused it or took it to the track etc car was all stock down to the tires (maybe replaced oem but not nitto etc.) My firend bought it with the poss of there being a spun bearing and at the price he got it for he'll still make out good if he has to get a rebuild but obviously he is praying that money can go toward heads/cam.

twelver12

iTrader: (3)

i have trouble believing that there is a single ls1 car out there that hasn been abused at some point in its life, i drive mine pretty tame but if i get a good straight shot with noone around you bet i take advantage of that

piston slap is kind of a sloshy noise and goes away in a minute or so

lifters would make a tapping noise as well as rods

the spun bearings aren so bad as long as you have a way to get the engine out and have a rotisserie, itll turn out to be a good thing replacing them

what kind of oil and filter are on this car also? i switched to a FRAM filter once and got all kinds of noises out of my engine so i switched back to DELCO and viola no more noise

99RTA

iTrader: (-1)

Piston noise usually gets quieter as it gets hotter...rod noise gets louder as the engine gets hotter. If a rod bearing is damaged you will also notice the oil has a silvery look to it when you change it.

You can easily find which cylinder is knocking by pulling off each injector plug one at a time until the knock stops. OR ANY GM dealer that KNOWS how to use a their tech2 can tell you which cylinder it is.


My 99 ta had a slight knock from new and we drove it 134000 miles without any trouble. Ls1 engines can be very noisy. The 02 Formula we have with only 31k miles is terribly noisy. It knocks slaps ticks geez! but doesn't use any oil and runs fine.

99blancoSS

iTrader: (115)

post a sound clip

eallanboggs

iTrader: (1)

If it's "really knocking" you'll hear it if you're in closed loop. Audible knock ain't good.

SOMbitch

iTrader: (8)

Is It white with orange stripes???? If so I looked at it in Kenansville a couple years ago and it had about 60K then. I passed due to the noise but have since heard it ran strong with no issues.

If it is PS it was the WORST case I ever heard and this is coming from a PS owner of a LM7 in a 99 Z-71. It was a good looking car though. After I heard it crank I didn't even take it for a ride because I thought it had a bad bearing.....

CarolinaCamaro

don't know where Kenansville is. his car is a nbm color w/o stripes.

CarolinaCamaro

will do asap. anyone know where any sound clips are of confirmed real rod knock or main bearing knock? I found one on youtube from kaliente but would like some others. also if anyone has info on clips of piston slap that was not later found to be rod knock etc.

Also is there any easy way to tell a lifter has collapsed? easier than taking them out?

BudH

iTrader: (3)

I have 3 LS1 Camaros. My 2002 has the worst PS of the 3 by far. Loud when cold - moderate to quiet when hot. Put 25k on the car with no change. After high speed/hot driving - silent for a few mins - then returns at a low level.

CarolinaCamaro

Thanks for the responses guys. couple of questions though:

I have heard the pulling the dipstip will be a tell-tale way to determine if it is real rod knock as the oil will appear silvery due to metal particles. So my questions are if particles are not found by pulling the dipstick could we eliminate rod/main bearings?
I was thinking we could take it to an oil changing place where you can see them work on it to see what the oil looks like when it is drained and to cut open the filter.

-I am not sure when he last changed his oil though and how many miles if any were put on afterward. So if only a few miles were put on since would this still be an accurate way to determine rod knock? What do you guys use to cut open the oil filter with? Will a compression tester be another way to check for real rod knock?

SOMbitch

iTrader: (8)

[QUOTE=99RTA;11922545]Piston noise usually gets quieter as it gets hotter...rod noise gets louder as the engine gets hotter. If a rod bearing is damaged you will also notice the oil has a silvery look to it when you change it. QUOTE]




Soooooo...... does it get quieter or louder as it warms up????

CarolinaCamaro

[QUOTE=SOMbitch;11931469]goes away for the most part after listening to it yesterday. only an occasional ting and when revving the motor there is "tinging" that matches rpm. I think its a flexplate issue due to the tinging- it doesn't sound like a rod bearing etc. and def not a lifter. due to location (back of the motor) this is my best assessment. noise disappears one warmed up and idleing but comes back with revving and goes away at idle. also it seems to be amplified slightly by the trans tunnel when in the car. It sound quite nasty when started though after it has been sitting for awhile (overnight). Also the tinging varies in pitch and "loudness" going from a loud clatter to a tinging to perfectly quiet but it ain't piston slap something is hitting something (flexplate imho). he is thinking of taking it to a trans shop to replace the flexplate. since it is a 2001 known to be weaker than 98-99 should he tell them to order a 98-99 flexplate to replace the old one or has GM corrected the problem (he doesn't want to go aftermarket) thoughts on this guys??????

BlackScreaminMachine

iTrader: (17)

Cold Piston Slap goes away after time. (warm up)

Bearing Knock will be always constant. (regardless of engine temp)

PCM scan software will pick up on KR.

Depending on the motor and valve train there maybe still "noise" but there is a softening of engine sound with cold piston slap.

blackcamarob4c

Does it sound like this? http://www.youtube.com/watch?v=AHQA3ChYOIM
If so, Prob Rod knock

CarolinaCamaro

Thank God No! He took it into a trans shop and the guy got under the car and pushed on the starter. He said that the starter wasn't disengaging and that was causing the "tinging" not a cracked/broken flexplate. I guess he should lube the starter shaft to fix it or does he need a new starter?