Normal rapping noise in engine

**05awdupstater** · 02-13-08 11:56 AM

The Caddy dealer has had my 05 V6 AWD SRX for two days. It has a loud rapping noise when starting cold. Lasts for 3 seconds or so. They confirmed the noise exists, but cannot figure out what is causing it. The dealer just called to tell me that I can pickup my car. It is not fixed. They need to setup an appointment with the area service rep from GM to "see if the rapping noise is normal or not". Exact words. Do any of you have this normal rapping noise?? Also, the dealer changed my oil about 3300 miles ago and it is black as night. They suggested I change it again to see if the noise goes away. Anyone else have the normal rapping noise and black oil after 3,000 miles or so? My 07 STS4 V6 does not rap and the oil is golden brown after 3,000 miles. What should I do next??

**c5 rv** · 02-13-08 12:15 PM

I ran my 04 CTS with the 3.6 engine for about 50K miles before trading and my current 06 SRX with the 3.6 engine has about 25K miles. Neither ever had/has rapping or cold start knock. I had a 99 Sierra and an 02 Avalanche, both with the vortec 5.3, and both with cold start knock for a few seconds on startup.

**srx2005** · 02-13-08 01:41 PM

2005 AWD V6. Still have vehicle and have never heard a cold start rapping noise in 33.5K miles.

**The Tony Show** · 02-13-08 01:46 PM

My '07 3.6L does it occasionally. Talked to my Service Tech and he told me it's the cam phasers, which sounds believable. The vehicle runs great and only makes 3 or 4 quick taps on startup, so I'm not worrying about it.

**King3244** · 02-14-08 12:37 AM

There is a tsb out on it. Google Cadillac tsb's for your particular year. I had an 04 N* that did it on cold starts when I got to 45,000 plus miles. I have the tsb at home.... unfortunately for you I am a snow bird and won't be back home for another 6 weeks. They fixed mine under warranty after I took in the tsb and showed it to them. They claimed that they couldn't find one when I told them about it. (aint the internet a wonderful thing)

It has to do with the tensioners for the overhead cams and is a well know problem.

I believe we also had a thread going on here....search cold start and see what you get.

**john d** · 02-14-08 01:06 AM

I hate rap too....change stations

**jmayhew** · 02-26-08 10:52 AM

Originally Posted by King3244

There is a tsb out on it. Google Cadillac tsb's for your particular year. I had an 04 N* that did it on cold starts when I got to 45,000 plus miles. I have the tsb at home.... unfortunately for you I am a snow bird and won't be back home for another 6 weeks. They fixed mine under warranty after I took in the tsb and showed it to them. They claimed that they couldn't find one when I told them about it. (aint the internet a wonderful thing)

It has to do with the tensioners for the overhead cams and is a well know problem.

I believe we also had a thread going on here....search cold start and see what you get.

can you post the link to the TSB.....my wifes SRX has the problem on cold startups...might bring up the issue when i take it in for the seal recall.

**RobVuk** · 02-26-08 11:33 AM

I have an 08 Northstar with 5,000 miles and it started making that noise on startup any time after a couple of hours of sitting. I took it in to the dealer. The cam phasers have been replaced to solve the problem. There is a pin that is supposed to drop to hold the cam timing until the oil pressure builds up in the hydraulically controlled phasers. It is NOT normal and if you have a warranty, I'd get it fixed.

The 6 cylinder also has VVT so I would guess it's a similar problem.

**73Thumper** · 02-26-08 12:48 PM

05awdupstater, geez, what kind of a dealer do you have? Just teasing, I had the same issue, my dealer also did not have a clue. As RobVuk stated - it was the cam phasors. (mine was/is a 2007) I brought it the TSB, but it did not help - they treated me like a idiot. They would need to consult with the area rep. and he told them - replace the phasors. Note - they wanted me to change the oil as well to see if it would help. (before they would call the area rep) I said I don't think so - you want it changed you pay for it as it only had about 1000 miles on it. The cam phasors are a known issue and tend to fail early vs late - mine only had 6000 miles on it. Also the description of the failure mechanism as RobVuk stated is right on the money.
Make sure they have the parts IN STOCK before they start the repair. This is not a 1 hour job, make them give you a nice loaner as I doubt you will have it back the same day.... After the repair mine did not seem as good as it was as new - but now the "rap" is subdued, lasts only 2 seconds max, and only after the car sits for more than a day or 2. I amy just be critical though - it runs strong with no other issues.

**05awdupstater** · 02-26-08 05:47 PM

Thanks for the replies. In regards to the cam phasers on the N* vs V6 VVT, I think I'll wait for the offical GM response. The dealer has a real good long time B/S artist as the service director. We had a hour long chat a few days ago and his tone of voice kept changing upon my questioning him. He was either making things up as he went along or his offical GM undergarments were creeping up somewhere dark. I bought 2 different Caddy's from two different dealers in the past 2 years. The '05 was Caddy Certified. It wasn't even close to being retail ready. Drove 2hrs to get to dealer. Long story, bad experience. Second dealer a little better but car was not 100% right and the paperwork was all F'd up after I waited 2 hours. I did receive my NYS Title today on the '07 STS with no lien on my offical ownership document. More mistakes seemed to have happened. Anyhow, the servicing dealer did not have anything close to the model and equipment I wanted on either purchase, so I am suffering from bastarditis. Most likely these will be the only 2 Caddy's in my career. I have been treated much better at the Chevy dealers than the GM Corporate flagship. Oh well, I guess the next hurdle will be the rate of depreciation these beauties seem to experience come trade in time.

**Tommy Trojan** · 02-26-08 08:12 PM

I'm guessing "piston slap" that I used to hear on my Olds van 3.4 V6 when cold or carbon buildup. After 30-60 seconds, the sound goes away - right? The piston slap was heard every morning, but the engine was still going strong when I traded the van in after 10 years. I learned to live with it.

**RobVuk** · 02-26-08 10:47 PM

Originally Posted by Tommy Trojan

I'm guessing "piston slap" that I used to hear on my Olds van 3.4 V6 when cold or carbon buildup. After 30-60 seconds, the sound goes away - right? The piston slap was heard every morning, but the engine was still going strong when I traded the van in after 10 years. I learned to live with it.

No. This only lasts 2 to 3 seconds until oil pressure pumps up. It's the cam phaser.