Hey, I just bought this car for my younger brother, its going to be his first car. Its a 2002 Z28 Automatic with 82K miles, when we test drove the car it sounded fine but when we finally driving it back home, I stepped on it a little and the car pulled as I expected for a stock auto, but seconds after that the check gages light comes on and the oil pressure is all the way down to 0. At that point I immediately put in in neutral, turn off the car and came to a stop on the side of the road, afterwards checked oil level and it was fine, then started up the car and oil pressure was fine. no noise yet. Finally, about 30 mins later the car starts making a knocking sound and at that point i thought I spun a bearing or something, but when i call the guy about it he told me it was a lifter, and i took it to a mechanic and he too told me it was a lifter.

Point is that if I were to leave the car sitting for a whole day, the next day it would make the noise, but after it warms up it would go away. So im not sure what to think so maybe you guys can help.

In this vid, the car was already preatty warmed up, probably sitting for about 30 mins or so after a drive.

http://www.youtube.com/watch?v=HAKA7...=youtube_gdata

im going to post another vid of the car and how it sounds after its been sitting for a while.

UPDATE: we took the car out yesterday after seafoaming the car just like in the write up, and we decided to step on it to see what happens. The car once again Ran as hard as a stock LS1 should but shortly afterwards the Oil Pressure went all the way down and we Pulled over and checked it. the Level was fine. We drove it back home and then it started knocking again really loud just as before ( the oil pressure was fine on the way back BTW) and shortly afterwards the noise subsided to the level in the video. Today I ran the codes and only got something about the EGR and the Catalytic converters. Nothing Else, but something I noticed was that the oil pressure is no longer as high as it used to be. Im starting to believe that the Oil pump has a Leak with the large O-ring and thats whats causing the noise. So when we run the car hard, the oil pressure going up aggravates the problem. Any ideas? Im thinking of removing the valve cover and running the car for a while to see if we could pinpoint the lifters making noise....

 

Could be piston slap and in need of a tune to put it very short.

 

Definitely not a spun bearing. It does sound like a lifter. I'd run a little seafoam in the oil for a hundred miles or so then change the oil. Should get rid of any sticking lifters.

 

I change the oil and put synthetic with mystery oil. Btw what is seafoam?

 

The baddest product on the planet...IMHO that is. I run it through the motor on all my cars and its a work of art. You can do a decent top end/bottom end cleaning and since it is 100% petroleum product you can run it in your oil and your gas tank.

Let me find the writeup for you. Pretty easy process. Just suck it through the booster hose into the back of the intake and then the deep creep version of seafom is in a spray can that you can get the front 4 cyclinders with through the TB.

Standby.

 

bingo.

https://ls1tech.com/forums/general-m...-your-car.html

 

Or another trick is to run some ATF in with the oil, usually replace 1 quart of oil with atf.

 

sounds like the noise mine makes, mines on the l/h side of the motor (when looking from the front of the car) i thought lifters too, but was told minor piston slap and gudgeon pin noise, was told ok though, not sure if this is a problem in America, but in Australia the first lot of ls1's around 1998ish through to 2001ish piston slap was a big problem, especially with oil consumption and later general noise.

 

it honestly sounds like the normal ls1 piston slap. something else must have gone wrong while you where WOT. i would change plugs out, change the oil and do some general maintenance and see if the problem occurs again. and also take it to auto zone or somewhere and have it scanned, report back when you get the codes

 

sadly mine makes this noise too... has since 80K miles and I just passed 140K. I keep hearing the words 'piston slap', but don't think thats the actual culprit. Good luck.

 

What exactly is going on when you have piston slap? Why isn't it a big deal?

 

IF it were piston slap, the piston which is traveling up and down is having contact with something. Were a piston traveling 800-6300 rpm to contact anything, it would most likely break what ever it's contacting or break itself. Lets just say this is bad. Which is why I don't think it's 'contacting' anything. It might just be a noise from the valve train, it might be a rub of the crank shaft, it might be alot of things, but I doubt it's 'piston slap'. Anyone else?

 

I have a piston slapping 5.3 in my truck and that is not piston slap...

I would GUESS it is a rod knock because it appears to be louder from the bottom and is on one side....

I will stress to you that nobody can 100% diagnose it from a video so I hope my GUESS is wrong.....

 

What happened in 1997 when GM designed the ls1 they decided not to correctly size each bore for a specific piston when assembling the engine as they had done in the past. So essentially what happens is that the skirt of the piston rocks slightly back and forth in the cylinder at low rpms causing the dull knock. Some motors do it and others dont my friends and I all have ls1's and out of the 5 weve had 3 of them slapped, some worse than others. GM has issued many service bulletins about it saying it doesnt hurt bla bla and for the most part the motors never ran any different all made great power. If you notice when the motor slaps if you rev anything over about 1500rpm the motor will sound normal. I thought mine was a bad lifter to and even replaced them all, still it didnt help its just something u learn to live with. The 02 cars are about the worst for it mine does it and consumes about 1/2 qt of oil every 3k miles not bad for a 100k 8 yr old car. Your car sound a lot like piston slap to me

 

I've never heard of a bad lifter causing a loss of oil pressure?

 

I don't think it is a bad bearing since the previous owner said he heard the sound before but the car ran formthe 2 years he had the car. I don't think that the car would run that long with a spun bearing. My concern now is that I bought the seafoam but I'm not sure if I should use it since there is still another cleaner( mystery oil) in there. What do you guys think? Btw the oil pressure has been normal since the last time.

 

Don't use mystery oil period.

 

sounds pretty normal to me

 

Sounds normal to me, I mean our engine do sound like sewing machines LS1/LS6!

 

If you actually had zero oil pressure and were still driving...not good dood. Ls1 engines are noisy for alot of different reasons. Low oil pressure is not in any way normal. If you actually ran the engine with zero oil pressure it did some kind of damage. I would pull the oil filter and pull cut it open to look at the filter media. That will tell you if any damage accured.