Help me diagnose this noise.
Thread Starter
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
Help me diagnose this noise. I don’t think this is piston slap. It does not happen when the motor is cold (like in the morning).
It is a clattering type sound that happens just after the motor is started and at low idle. It gets pretty loud sometimes, but seems to go away if I bump it up to about 1500 rpms, then it is gone until the engine sits for a decent amount of time, but not too long. It seems to only happen when the oil is hot, but the motor has had a chance to cool. It also seems to be coming from the right valve cover. I think it has something to do with oil not getting up there quick enough or some type of carbon deposit.
I just wanted to get some opinions. I’m also experiencing a little KR even though I have lowered timing quite a bit (this is a FI motor), so I think I’m going to try some topend cleaner as my next step. This noise has been around since the car was pretty new and before any mods were done, but it does not seem to follow the normal piston slap behavior (I never hear it when the motor has been sitting over night).
It is a clattering type sound that happens just after the motor is started and at low idle. It gets pretty loud sometimes, but seems to go away if I bump it up to about 1500 rpms, then it is gone until the engine sits for a decent amount of time, but not too long. It seems to only happen when the oil is hot, but the motor has had a chance to cool. It also seems to be coming from the right valve cover. I think it has something to do with oil not getting up there quick enough or some type of carbon deposit.
I just wanted to get some opinions. I’m also experiencing a little KR even though I have lowered timing quite a bit (this is a FI motor), so I think I’m going to try some topend cleaner as my next step. This noise has been around since the car was pretty new and before any mods were done, but it does not seem to follow the normal piston slap behavior (I never hear it when the motor has been sitting over night).
TECH Enthusiast
Joined: Nov 2002
Posts: 593
Likes: 1
From: Chicago Heights, IL
Re: Help me diagnose this noise. Other things known to cause clattering noises:
1. PCV valves. I guess GM redesigned the PCV system and all 98s and maybe even some of the 99s had a design which caused them to make clattering noises. Since you have a 2002, I seriously doubt this is it.
2. AIR check valves. If they go bad, (usually after installing LT headers without AIR restrictor plates) they will tap. Once again, I dont think this is your issue.
3. Lifters. The lifters on all LS1s are known to be noisy. If you upgrade to aftermarket ones, it gets even worse. Lifter tapping sounds very similar to piston slap.
4. Piston slap. You have a 2002, and piston slap is a very likely cause of your noise. I realize that not all your symtoms point to piston slap, but considering the year of your car, I would say its the most likely cause.
Good luck in getting to the bottom of everything.
1. PCV valves. I guess GM redesigned the PCV system and all 98s and maybe even some of the 99s had a design which caused them to make clattering noises. Since you have a 2002, I seriously doubt this is it.
2. AIR check valves. If they go bad, (usually after installing LT headers without AIR restrictor plates) they will tap. Once again, I dont think this is your issue.
3. Lifters. The lifters on all LS1s are known to be noisy. If you upgrade to aftermarket ones, it gets even worse. Lifter tapping sounds very similar to piston slap.
4. Piston slap. You have a 2002, and piston slap is a very likely cause of your noise. I realize that not all your symtoms point to piston slap, but considering the year of your car, I would say its the most likely cause.
Good luck in getting to the bottom of everything.
