spin-doktor

Coming home from work today, I back the vette into the garage as usual ( 2008 3LT Z51 with NPP) and all the sudden i notice a metallic rattling noise coming from the back of the car, WTH so i leave the engine running, step out and head towards the back.

NPP valves in normal "closed" position.

VIDEO:

http://img190.imageshack.us/i/npprattle.mp4/

Im pretty sure the noise is coming from the valves in the NPP mufflers. I got back in the car and manually opened and closed the valves using my NPP manswitch and the noise went away completly. However, this has happened before and im sure it will happen again.

Has anybody else experienced this issue ? What was the solution ? Did you need to have the mufflers serviced or replaced under warranty?

- Mark

Swiftrider08

I have heard this a few times a never thought much about it.

The NPP valves use a mechanical linkage from the actuator to the valves. The pivot points of this linkage are loose (or a sloppy fit) to take into account road dirt, salt and other items that may buildup on the linkage over time. The sloppy fit allows the linkage to always function under most all conditions.

I believe what happens is that from time to time the valves open or close in just the right position that this "slop" (or tolerance in engineering terms) is at its' maximum and thus the linkage/valves rattle. Not a thing to be concerned with in my opinion.

0SonOfDreams

if you have a vacuum leak this could happen, they need 14"HG to stay shut and thight, a little leak in the actuator or line could cause this. Other cause is a loose rod/nut on the actuator arm. You need to touch spots and see what stops the noise.

NYC6

I would put on a thick glove and try to isolate exactly where its ratting from, by holding individual parts you should find out where to focus you attention.

DaveC6

I put NPP on my '07 and they rattle for a second or two when I close them. I always wondered if that was normal. Sounds like your video only it lasts for only a second or two.

PabloCruZ06

My dealer (Boardwalk) serviced that under warranty. Here's what the service work order said: "Racked vehicle found hinger springs for exhaust rusted, need to clean and coat with anti-seize lubricant. Removed both exhaust hinger springs, cleaned and coated with anti-seize lubricant. Road tested, metallic rattle noise not heard."

Dif

With the NPP exhaust,... that rattle can come from one of the Butterfly flaps.
If you grab the top of the linkage, where the rod goes down into the Butterfly valve, you'll find there is slight "Up and Down" play.
That's all it is.
Sometimes it might rattle .. sometimes not.

It'a muffler pipe and not a precision fit type thing.

And as you noticed, just open and close it .. and it goes away until maybe the next time it rattles a bit.
I noticed it once when I was standing in back of the car and just touched the top of it and it stopped it.

Just the nature of the beast

spin-doktor

thank you for all the responses everybody

xgto

I think I have a fix, The pivot point for the butterfly's have too much up and down play. this has only happened on my right side muffler. I took some thin picture hanging wire and wrapped it around the pivot point one time and so far the rattle has stopped. I think that a C-Clip type washer may be better to take up the slack which I will do next.