: Sort-of hesitant to ask about this; but here goes..



WhoseCadillacIsThat
01-20-12, 07:10 AM
Tapping from rear of vehicle. Sitting at a stop light I heard a tap, tap, tap ,tap, tap from the back of the car. Five taps in rapid succession then maybe two more a little later..... I'm telling the truth! I have heard it a few times and it doesn't seem to be at a given time with engine temperature, or obvious reasons - very random. This morning wile the car is warming (sitting still), I'm standing behind it talking with my wife and we both heard it. Five taps that seemed to come from the right rear..... WTF? Resonator expansion? I have no clue.... The first time I heard it sitting at a stop light I actually thought someone was tapping on the back of the car.

It isn't objectionable but is something that should have some plausible explanation. The trunk is empty... no-one is in the trunk! Has anyone heard this or would anyone admit it if you did?

Come on - anyone....

smackdownCTSV
01-20-12, 07:49 AM
Half dead hooker in the trunk?

Try and record it. Bring it to the dealer. Do the road test with them.

WhoseCadillacIsThat
01-20-12, 08:03 AM
The hooker is tapping too fast...she's still in good shape!

How about a lifter....cam follower - maybe sticking for a short period...? But sounding like it's from the rear....doesn't seem right.

Yeah, off to the dealer again.... The nav system locked up a few days ago - straight to the dealer. We'll get this car broken in soon we hope.

I know how to make it stop - sit behind the car with a recorder....it'll never do it again.

M5eater
01-20-12, 08:20 AM
Mine makes that noise too when I first start it up. I want to say it's a faulty evap solenoid. That's what it was in my G8. Infact I need to tell hall about it, Thanks for reminding me.

Cadillac Cust Svc
01-20-12, 08:20 AM
I have never heard of this happening before. I would contact your local dealer to have them diagnose/repair this issue for you. If you would like me to call and make an appointment for you just let me know. In the meantime, if you want to you can send me your VIN number and I can see if I can find some more information out about this. If not, keep us updated.
Breanne
Cadillac Customer Service

Silver -V-
01-20-12, 10:58 AM
I have the exact same thing happening. It happens about 5 minutes after start up, and usually when idling. I notice it when I am dropping the kids at the bus stop in the morning. Just a few taps, like someone is strumming their fingers on the rear of the trunk lid.

elphil
01-20-12, 12:11 PM
Maybe it's a Sedan thing. Any Coupes or Wagons have this tapping sound? If your subwoofer is in the spare wheel well, maybe it needs tightening down.

M5eater
01-20-12, 12:25 PM
it's not the sub..

FLTRI
01-20-12, 12:43 PM
I chased an 1800 RPM tap/vibration/resonance in my 96 Vette for almost a year. Ended up being the exhaust making contact with a cross brace. The sound, sounded nothing like what it actually was. Put it on a rack and check exhaust clearance from front to back...

Fixed mine in about an hour, once I finally found the problem...

Caddyscat
01-20-12, 01:10 PM
I have heard it too on several occasions as well. It kinda startles me, sounds just like someone tapping on the right rear quarter.

lilred
01-20-12, 02:48 PM
That's just the trunk monkey, rolling over in his sleep...

WhoseCadillacIsThat
01-20-12, 03:05 PM
Well, I sure am glad I'm not the only one hearing this. It made me quit drinking, quit making obscene gestures at other drivers, and quit having immoral activities with my wife. Whew, now I can go back to the nice fellow that I was before.

----------


I chased an 1800 RPM tap/vibration/resonance in my 96 Vette for almost a year. Ended up being the exhaust making contact with a cross brace. The sound, sounded nothing like what it actually was. Put it on a rack and check exhaust clearance from front to back...

Fixed mine in about an hour, once I finally found the problem...

I had thought about that situation but the taps are much too timed and spaced. The taps are very precisely timed and there are five distinct taps. It does remind me of a sticking hydraulic lifter but again - why just five taps as if they are programmed? It doesn't sound like the exhaust system, it sounds like someone tapping five times on the right rear fender with their fingernail.

M5eater
01-20-12, 04:07 PM
I had thought about that situation but the taps are much too timed and spaced. The taps are very precisely timed and there are five distinct taps. It does remind me of a sticking hydraulic lifter but again - why just five taps as if they are programmed? It doesn't sound like the exhaust system, it sounds like someone tapping five times on the right rear fender with their fingernail.

yup. This is exactly what it sounds like, there's abolutely no deviation or possible explaination other than this is some solenoid or valve that is clicking

e6t
01-20-12, 04:11 PM
cannot duplicate.

LFTW8S
01-20-12, 05:22 PM
I've heard the same in the right rear of both my 2010 and 2011 V-Sedans in the morning sitting in the garage warming-up. Still don't know what it is???

tedcmiller
01-20-12, 07:42 PM
The sound is probably related to heating or cooling as the car warms up or cools down. Might be parts or brackets touching that shouldn't be touching. If the noise doesn't cause any running or performance problems, I probably wouldn't worry about it.

WhoseCadillacIsThat
01-20-12, 07:55 PM
The only very obvious item in that location (Rt Rear) is the battery.....and what else? Never heard a battery make any noise like that. There is also the fuel fill. Maybe the fuel cell troll is saying something like - 'don't - you - know - I'm - out' ; tap-tap-tap-tap-tap..... getting silly again...

I attempted to purchase the service manuals for this car but Helm put my money back into my account - said they were 'out of stock'. This is a good reason to have some manuals to check.... Might shed a bit of light on this. I like to look at those line drawing graphics too, trying to figure out what the hell I'm looking at.

Unclemelty
01-20-12, 08:20 PM
The only very obvious item in that location (Rt Rear) is the battery.....and what else? Never heard a battery make any noise like that. There is also the fuel fill. Maybe the fuel cell troll is saying something like - 'don't - you - know - I'm - out' ; tap-tap-tap-tap-tap..... getting silly again...

I attempted to purchase the service manuals for this car but Helm put my money back into my account - said they were 'out of stock'. This is a good reason to have some manuals to check.... Might shed a bit of light on this. I like to look at those line drawing graphics too, trying to figure out what the hell I'm looking at.

Purely a guess here, but the "fuel cell troll" statement (funny stuff by the way) kinda got me thinking, considering that fuel systems of today are pressurized could this sound be the fuel cap equalizing the negative pressure after the system expends a bit of the fuel in the tank? Just guessing...

CTS NV
01-20-12, 09:42 PM
Funny -- I used to hear the same sound early in the morning when stopped in traffic. I thought it was someone outside tapping.

The noise vanished after my car was rear-ended pretty hard one day, destroying the exhaust, which had to be replaced. I wouldn't recommend this as a solution ;)

GAGS-V2
01-21-12, 02:53 AM
LoL! You guys crack me up! I have the same noise. Only does it when I let it warm up with either no load or light driving and then stopped at a light or pulled over a few minutes after start up. I have never had it while driving. I must say, the first time it did it, scared the krap out of me. I wondered whohit my car or what was alive in the trunk. I thought about trying to record it but I know it will never do it when I'm trying to get it to do it. Thanks for posting this, i thought I was the only one. By the way, 2011 Coupe here, so it's not all sedans.

shchow
01-21-12, 09:26 AM
Do you notice any correlation to brake or throttle application?

M5eater
01-21-12, 09:41 AM
Do you notice any correlation to brake or throttle application?
nope. I hear it while in park.

RippyPartsDept
01-21-12, 10:48 AM
maybe evap vent solenoid valve?

M5eater
01-21-12, 11:04 AM
maybe evap vent solenoid valve?
That's what I'm thinking.

WhoseCadillacIsThat
01-21-12, 12:55 PM
maybe evap vent solenoid valve?

So is the valve sticking and 'chattering' as it opens? Sounds like maybe a defective (brand new) solenoid valve.... I haven't looked for any codes - may be a good idea to do so.

RippyPartsDept
01-21-12, 01:03 PM
That's a decent hypothesis ... possibly proper operation of the vent valve combined with something else that lets the sound transfer .. maybe not mounted correctly or something is touching it

HEDP-V
01-21-12, 06:24 PM
M5eater, I have been hearing that same exact noise in the same exact spot for nearly two years now. I usually here it when I start up the car, and i usually hear 4 taps instead of five. I have an 09 sedan with no mods and this noise has baffled me also. I thought my car was haunted or something. I never gave it any thought and just assumed that it was some sort of noise that was caused by something expanding or contracting.

hulksdaddy
01-21-12, 06:32 PM
Anybody ever hear it from outside the car?

HEDP-V
01-21-12, 06:40 PM
I haven't heard itfrom the outside as of yet. Its always happened while I've been inside the car.

hulksdaddy
01-21-12, 06:47 PM
If it does it regularly, I'd have someone outside, see if they can hear it.

Could be a relay. In my vettes, whenever I stepped on the brake pedal, always heard a clicking. Maybe similar?

WhoseCadillacIsThat
01-22-12, 01:29 AM
Anybody ever hear it from outside the car?

Yes, heard it standing at the back of the car as the very first post explained.... Heard it both inside and outside - five taps then sometimes a little later a couple more taps. It's a miniature leprechaun drummer practicing his para-diddle. So basically almost everyone is hearing it so the dealers should have already encountered the noise before.... we'll see.

----------


Funny -- I used to hear the same sound early in the morning when stopped in traffic. I thought it was someone outside tapping.

The noise vanished after my car was rear-ended pretty hard one day, destroying the exhaust, which had to be replaced. I wouldn't recommend this as a solution ;)

Not a pleasant thought, not at all.... the drummer was killed.

GAGS-V2
02-01-12, 02:16 AM
OK, so after reading this thread I decided to see if I can get it to do it when I'm ready for it. The past two mornings, I start the car ( 2011 coupe, six speed manual), back it out of the garage and let it idle in the driveway. After a few seconds longer than four minutes of idle (and the water temp a hair over 150) here comes the dreaded 5 knocks from the right rear. I'm going to try it and be outside of the car in the next day or two and then let you guys know what I found out. As I said, both times it started when the water temp went a hair over 150. It won't do it if I'm driving it.

WhoseCadillacIsThat
02-01-12, 07:25 AM
OK, so after reading this thread I decided to see if I can get it to do it when I'm ready for it. The past two mornings, I start the car ( 2011 coupe, six speed manual), back it out of the garage and let it idle in the driveway. After a few seconds longer than four minutes of idle (and the water temp a hair over 150) here comes the dreaded 5 knocks from the right rear. I'm going to try it and be outside of the car in the next day or two and then let you guys know what I found out. As I said, both times it started when the water temp went a hair over 150. It won't do it if I'm driving it.

Welcome to the club! I still intend to get this car to the dealer about this....but I hesitate having to leave it there so someone can attempt to duplicate the problem - 'tomorrow or the next day' - This has also happened in traffic sitting at a stop light and no, it hasn't been heard while under way.... strange... The evaporator solenoid valve actuating makes the most sense but why doesn't anyone at Cadillac know about this? The phenomenon is not isolated to just a few cars it seems...

AMRAAM4
02-01-12, 09:50 PM
Gentlemen, there is nothing wrong with your cars. The same thing happens on the late model GTOs. Particularly in cooler/cold weather a little after start up. As already stated, evap canister