Knocking sound

[mack1a]

I know I have seen something on the following somewhere in this forum but I can't find it. I probably am too impatient to wait for a search on this site.Twice when I have stopped at an intersection about 1 mile from my house I have heard a knocking sound that sounds like someone is in the trunk. It happens 5 or 6 times then disappears.Again, I know I have seen this on the forum but can't find it. I believe it was something to do with the fuel system. I would appreciate someone refreshing my memory on this if possible.

[mack1a]

The knocking (5 times) has happened twice more since the original post. I sounds just like someone is rapping the side of the car with their knuckles. Only happens at the same stoplight when I catch a red light when leaving my subdivision.

[cubldr]

Originally Posted by mack1a

The knocking (5 times) has happened twice more since the original post. I sounds just like someone is rapping the side of the car with their knuckles. Only happens at the same stoplight when I catch a red light when leaving my subdivision.

I replied to another similar post also so we are not alone. My 06 DTS does the same thing. It happens when the car is still fairly cold in the morning and about a mile or two from the house. Interestingly today, the light at the same intersection where it usually does this was green for a change and I actually heard the four knocks as I was drving through the intersection while moving (albeit slowly) It has happened frequently when stopped and my kids were in the back seat and they tell me that it sounds and feels (they feel the vibration of the knock) from the floor boards, not the trunk even though it sounds like the trunk from where I sit. I only have 2k miles on mine and haven't had it in the shop yet.

[Lanzz]

Same noise in mine - always when the car is not quite up to operating temperature. No idea what it is, but I read somewhere on this site that it is something that is normal so I never bothered to ask the dealer. I have 9,000 miles right now, has done it since it was new.

[mack1a]

Originally Posted by Lanzz

Same noise in mine - always when the car is not quite up to operating temperature. No idea what it is, but I read somewhere on this site that it is something that is normal so I never bothered to ask the dealer. I have 9,000 miles right now, has done it since it was new.

The noise may be common, the noise may be pervasive, the noise may be a lot of things, but, the noise isn't "NORMAL". $50,000 cars do not have normal sounds that remind one of rapping on a tin roof. Now Cadillac may think this is normal and we all know that Cadillac service will not fix the sound unless they hear it as they never believe anything you say.

If we are passive enough to accept this as "NORMAL" they will add another "NORMAL" noise next year. And they will then charge you for the extra value of the added noises the following year.

If every $20,000 car on the rad had this same noise I might accept that there is no alternative. Hint, they don't.

I would give anything to bring this sort of thing to the new Cadillac Director of Quality.

[Jesda]

So its

1) When cold
2) Regularly occurring
3) From the rear

What is in the trunk/rear area that uses a fluid that may warm up?

[mack1a]

The performance on ths site is so bad that I never get a search to complete satisfactorily.

I entered info earlier and couldn't find it

I searched the symptom on the internet and found the old record much easier. The hit right here on the Forum that adds a lot of info is located at:

The URL is http://www.cadillacforums.com/forums...m/t-80211.html

There are a couple of sound issues there. Go pretty far down and read earlier postings on this issue.

We are fools if we accept this as normal operation.

[Jesda]

In that thread, exhaust is mentioned as the possible cause. Do you have another dealer you can contact?

[mack1a]

My scenario is described perfectly in that entry as it doe not fail over 60 degrees of so, and believe it or not, it has always failed at the same stop light about 1 mile from my driveway. It won't fail if I catch the green light and don't stop. The only time it didn't fail under the right scenario was a rare cool morning (about 48 degrees) when I deliberately let the car idle for about 10 minutes and then managed to catch the red light, it didn't fail (apparently because it was warmed up more).

It only fails once per day and is always 5 or 6 rapid knocks. It really sounds like someone rapped te side of the car. I catch myself looking in the side mirrior every time it happens.

So, I don't think this is an exhaust issue. I had a loose baffle in one of my Corvettes and that was an entirely different failure scenario.

If I take it to another dealer I will just be letting mine off the hook.

I truly like my fully loaded DTS performance Level. I am annoyed that they messed up the clock, the computer interface and the adaptive CC issue just gets strange looks when I bring it up. But nothing is perfect and I still don't want to own cars built by non US headquartered companies, especially former WWII enemies.

[rjm]

Mine started the same thing during the holidays, and I finally took it for an oil change and mentioned this to the dealer. First diagnosis was the exhaust, but after further inspection, I was informed it is the load leveler. RIGHT.....

I didn't go into detail with the tech since he is new to the dealer, but I don't think I've owned a car that did not have the load leveler and its never made this type of sound. I'm sure this will continue, and I'll continue to take it to the dealer. After more time, maybe the cause will come to light.