Like most second generation CTS-V owners, I’ve come to terms that to own the ‘fastest sedan in the world’ I have to endure a sound that can only be described as a can full of marbles, being tossed-about under the hood.
Several CTS-V owners have experienced this issue which resulted in General Motors releasing a Technical Service Bulletin (TSB: PIP4523A) which basically states: the rattle is normal, take your $73,000 car and live with it.
CTS-V owners, like most performance vehicle owners, are very active online. Owners took to the forums to discuss and share their displeasure with ‘the rattle’. They made enough noise that in November of 2009, it prompted Ed Piatek then Program Engineering Manager on the CTS-V to step in and clarify a few facts. Below is the response Ed provided to members of CadillacForums.com:
I’m Ed Piatek and I’m the Program Engineering Manager on the CTS-V. I recognize that this forum represents the thoughts and experiences of some very passionate owners and enthusiasts, and appropriately many of us on the engineering team periodically review this and other forums to keep our finger on the pulse of this important group.
While we cannot respond or comment on every post or question, the number of comments and degree of inaccurate information around supercharger shaft wear merits an engineering response to set the record straight, and assuage any concerns of our V series owners. Here is the response from our engine experts:
The torsional isolator is used in the CTSv LSA engine to isolate potential gear rattle noise during idle. The isolator contains a torsional spring that fits over the shaft. Purpose of the shaft is to distribute the stresses in the torsional spring. As the spring goes thru its travel, the inside of the coils can contact the shaft. The spring material is intentionally harder than the shaft which by design results in visual witness marks and/or limited wear on the shaft. The witness marks and/or limited wear is expected and has been observed on all the Eaton component durability tests, GM engine and vehicle durability tests and on customer vehicles with no impact on the functionality of the spring and isolator. The shaft and isolator are in a sealed cavity, separate from the rest of the supercharger and engine.
Q: Will this shaft wear harm my engine?
A: No. The visible wear will not damage the engine. The supercharger and the engine were tested and successfully validated to meet all GM durability requirements…which are much more severe than any customer usage.
Q: What causes this wear?
A: The isolator contains a torsional spring that fits over the shaft. The purpose of the shaft is to better distribute the stresses in the torsional spring and prolong its life. As the spring goes thru its travel, the inside of the coils can contact the shaft. The spring is a harder material than the shaft…so that when there is contact, the spring will not potentially break. If the spring breaks, then the torsional isolator function is lost.
The following pictures show in detail the wear described above by the Cadillac engineers and was provided by member Heavy H2O of CadillacForums.com:
In the picture above the GM isolator is the one on the left and the community-sourced isolator (aka ‘The Fix‘) is on the right.
DIY to the Rescue
In an effort to resolve the problem, CTS-V owners created their own fix – installing a solid isolator without the abrasive metal spring inside. And whatta ya know – silence! (or as silent as a supercharged 6.2 liter can be). This also means the shaft is no longer being disintegrated.
Why didn’t GM address this issue earlier? It could be because the supercharger is sourced directly from Eaton assembled. As I was told by a GM service tech, “we are prohibited from taking apart that supercharger.”
It’s also important to note that many service managers have explained to customers that any further damage to the supercharger could not be covered under warranty, if the owner opened up the supercharger and installed a non-GM part. Like the solid isolator above.
Enter the new LSA
In a post today by user smackdownCTSV of CadillacForums he pointed out that according to a diagram of the 2012 LSA on GM’s media page the new LSA will no longer have the internal spring in the supercharger isolator (See below).
Did the engineers have an epiphany? Or did they come to the same conclusion that the rest of the CTS-V community did – uhh…that sound ain’t NORMAL.
A representative from Cadillac Customer Service provided the following feedback in the forum discussion:
If this is a widespread concern, I am happy to document it for further consideration by my superiors. I am unfamiliar with this forum as I am filling in for Katie until Wednesday; are there other threads regarding the supercharger rattle you’ve described here? What model year(s) is this prevalent in? I would like, if you all are interested, to document your username(s) if you own a CTS-V with this concern.
Cadillac Customer Service
While Cadillac seems interested in this issue now, the bigger question will be if GM is willing to issue a TSB for repair/replacement of a part that isn’t a safety issue. If what the service advisors have told me is true, about not being able to repair the supercharger, GM will be required to recall the entire supercharger rather than issuing a TSB for a new isolator…which could be the very reason the General has been mum on the issue from the start.
Either way, GM or the supercharger supplier need to come up with a solution and make this right. Either allow GM service technicians to install a new isolator or recall the entire unit.
Link to the thread on Cadillac Forums: GM Found a Fix to the Supercharger Rattle
UPDATE: The video below was filed on March, 19 of a 2009 Cadillac with 29,000 miles on it. Hopefully this will provide readers with a better idea of the sound produced by the damaged isolator.