2005 Cadillac engine makes tapping noise on cold start. Noise eventually goes away. Low mileage, but dealer never diagnosed or fixed when first owner had under warranty. Dealer now diagnoses it as noise caused by cylinder sleeves, and says the noise doesn’t cause any problems, and there is no repair guaranteed to eliminate the noise except to possibly replace the cylinders.
Tapping sound is more likely dry lifters to me.
Asked dealer about oil possibly not getting to lifters, but mechanic says it’s not the lifters making the noise, but the cylinder sleeves don’t expand until engine warms. I don’t know, and I haven’t been able to find a discussion of this issue on the internet.
Consider adding a fuel system cleaner with PEA in it. CCDI could be the conditions. Combustion Chamber Deposit Interference. It can produce the metallic sound that contours your described time line. Amsoil PI, Techron, Gumout Regane Complete.
I’d also use Auto-Rx prophylactically just to rule out any fouled oil passages.
Thanks. I will try that. Perhaps that will help the lifter problem as well. I will report back on what happens.
I’m not sure if the Northstar engines were subject to this, but many GM V8 engines over the years have suffered from ‘piston slap.’ I myself have had a Chevy with this problem. When cold, it would make the noise you describe. The noise would gradually subside as the engine warmed up. If this is what you’re experiencing, it’s an embarrassing noise, but shouldn’t really cause any harm.
Maybe someone else can confirm whether this engine is subject to the infamous piston slap problem.
The NorthStar engine was derived from a Lotus design intended for racing. It has double overhead cams and a split crankcase…They made a V6 version called a BabyStar…A loose sleeve could indeed produce a tapping noise but so can piston slap. Both are relatively harmless but the only real fix is a new factory short-block and in your case, I don’t think that’s going to happen…It is interesting to note that when Cadillac went to play with the big dogs with the CTS=Z they used a pushrod Chevy Small Block, not the NorthStar…
Thanks, gentlemen. Based on the comments of the Cadillac dealer’s expert/troubleshooter, it is likely a loose sleeve. Dealer’s service manager said he was going to speak with GM about what they can do. I purchased a pricey extended warranty from the Lexus dealer which sold me the car, but I don’t think the warranty will cover something which existed during the Cadillac new car warranty period. I want to add that the original owner reported the noise 3 times during the first 5 years, but the dealer never corrected the problem. I am also concerned that the loose sleeves may cause problems in the future.
Since there is nothing really “wrong” with your car that limits its serviceability, and the noise stops when warmed up, and it’s been going on for 5 years, and GM is bankrupt, the chances of getting a replacement engine out of GM or your worthless extended warranty is slim to none…