08msmZ06

Hey guys, I need some advice. Tonight I went for a highway cruise and after about 10 minutes at 70 mph in 5th the motor started tapping. I continued on for another 10 minutes or so and then exited the freeway briefly to head back home. The tapping stopped, so I nailed it on the on-ramp. The car was strong and all the temps were normal. The tapping resumed when I dropped it in 5th at 70 mph. It tapped all the way until I exited the freeway and dropped to the lower gears. No tapping from that point on. The car stayed strong and all the temps were normal. My last oil change was about 3600 miles ago. I had metal shavings on the drain plugs, but the oil changer at the dealer wiped them before showing them to an engine mechanic. Even so, I asked an engine tech to take a look, and he checked my filter and everything else he could think of for signs of something coming apart in the motor, to no avail. The car has been fine/quiet until tonight. What should I do next? When I pulled into my garage at home the motor was quiet like nothing happened. The only other thing I've noticed in the past couple of days is that the motor starts roughly after sitting for a while (overnight, etc.). It revs high briefly and makes a kind of grinding noise and then starts idling normally. I think the harsh startup and tapping noise are related, but I have no idea what could be the problem. Suggestions are greatly appreciated.

Note: I should clarify that the engine tapped for the first time the day before my last oil change, 3600 miles ago. It tapped the exact same way while cruising in 5th at 70 mph. It had not tapped since then until last night. I've had the car for a little over three years, and it now has 32,062 miles on it. No track duty. It's strictly a DD, but I do drive it hard as often as possible.

tim414

Don't do anything differently....continue to keep oil changed at regular intervals. Mine does same thing. It's a 2010. I've heard it since day one when I drove it home (125 miles) and it had 6 miles on it (new). Now it just turned 4k miles and had 1st oil change last week.....these have noisey valve trains. You should be fine.

edit: my LS3 did same thing that's why I listened for it when my 'Z was brand new!!

PabloCruZ06

Could be the dry sump o ring issue. See this link:

http://forums.corvetteforum.com/c6-z...-and-pics.html

The TSB for the issue is in the thread.

tim414

My ticking/tapping noise sounds as if it comes from the passenger side of engine. It's a tick or tap noise and almost makes me think it's lifters or fuel rail noise....I had a Camaro that had a lifter go bad at 95-105k miles....but not exactly same sound

My 'Z (2010) seems to emit this sound at around 1200-3000 rpm....definitely in sync w/engine rpm....I thought at first while it was "breaking-in" it had used some oil but last week when we changed oil-the last round hole on the dip stick (from top fill mark on crossed hash marks of dipstick indicating full) did not have any oil on it after 10.5 qts was added during oil change. That was same mark when I first thought it used some oil when actually it had 10.5 qts already. So maybe it only used maybe 0.25 qt....

But, what confuses me is I think my LS3 emitted the same sound so it makes me think nothing is wrong. Although the LS3 is a different engine having 'wet-sump' rather than dry-sump....since I parted with it to buy my LS7 I cannot compare (don't know why I would anyway since their not same engines).....or I had read one post that stated that fuel rails were same and the material their made of can transmit engine noise....anyway....

It's under warranty so I'm choosing NOT to worry about it. If it gets louder or does anything differently then I'll post and take it in to be checked....meanwhile I'm choosing to be happy with my LS7....

08msmZ06

Does anyone have any thoughts on what could be causing the harsh startup after the car has been sitting for a while (overnight, etc.)? It revs very high briefly and makes a kind of grinding/rattling noise and then settles into a normal idle. This harsh startup also occurred when my engine tapped the last time. After I changed the oil the last time both the tapping and the harsh startups stopped. The oil is always changed within the normal cycle (oil life approx. 20% left; 4000-4500 miles, tops) Thanks.