: Horrible buzz/rattle when decelerating or clutching in



The Tony Show
10-13-08, 10:06 PM
The title pretty much says it all- I have an absolutely disgusting sounding rattle/buzz coming from somewhere under the car when either letting off the gas in gear or pressing the clutch to shift. It's definitely tied to RPMs, and much more noticeable at higher revs.

If I had to guess, it sounds valvetrain related. It's always been there, but has been downright terrible since adding the headers a year ago (since the stainless acts like an echo chamber vs. the cast iron manifolds). I'm hoping I'm wrong, but running out of ideas. My Corsa is welded so it's not a leak, I've changed header gaskets three times and smoke tested those for leaks, and I even cut out the Corsa mufflers and replaced them with Magnaflows- still sounds like a big can of rattly ass when I let off it. It's at the point now where I can't even enjoy a drive with the windows down.

Sugestions? Anyone else had the problem and cured it? Commence speculation!

darkman
10-13-08, 10:42 PM
My guess is that either a weak, but not broken, exhaust valve spring or a defective hydraulic lifter has given you a Jake brake effect.

The Tony Show
10-13-08, 11:01 PM
Yeah, that's what I was thinking (although not that detailed). Hrm. I suppose there's no easy way to tell for sure without pulling the valve covers. eh?

CTSV_510
10-13-08, 11:06 PM
When you pull the valve covers, a defective lifter may be more obvious, but how do you determine a weak, but not broken valve spring? :confused:

Chef
10-14-08, 01:17 AM
valve springs...:alchi:

rand49er
10-14-08, 07:01 AM
valve springs...:alchi:Whoa! Chef's lurking! Hi there!

On top of that, I'd say you guys are right. Swap out all sixteen for new ones ... can't be a huge job ... can it?

CIWS
10-14-08, 07:30 AM
valve springs...:alchi:

Hi lurking Chef :D

The Tony Show
10-14-08, 08:38 AM
Holy crap- I pulled Chef out of retirement! What's up, man?

Your sound pretty sure of the valve spring diagnosis. Is it safe to assume you suffered the same symptoms, and that was the cause?

RightTurn
10-14-08, 08:38 AM
:yeah: Hi, Chef!! :wave:

Tone, I have no idea what the problem is. ahahaha. :tard:

The Tony Show
10-14-08, 08:41 AM
Thanks Artie. I already tried yelling at it and giving it an extremely annoyed look- neither worked. :D

RightTurn
10-14-08, 08:52 AM
OK, well you've used all my expertise, save for calling it a "POS Dodge" or something. I'll move along. :coffee:

Chef
10-14-08, 06:54 PM
:alchi:yes and what was left of the little bits of metal on two...

Hi all!

The Tony Show
10-14-08, 06:57 PM
Yikes. :suspense:

Since I've had the noise for over a year, I "hope" it's nothing major that involves metal shavings. Darkman's theory of a fluttering exhaust valve due to a weak spring sounds like it could cause the "flapping" noise I've been posting about for a while now, even though I've always thought it was just the infamous "piston slap" that a lot of 'Vette owners complain about.

I'll be checking it with a stethoscope tomorrow to try and narrow it down to at least one side, hopefully to a particular cylinder. I'll also be checking the pulleys to see if there's any wobble or bearing noise there, and will report back. Feel free to chime in with any other theories!

darkman
10-14-08, 08:03 PM
You might start with a compression /cylinder leak-down check to see if one cylinder differs significiantly from the others.

a64pilot
10-14-08, 08:08 PM
Pressure plate or throwout bearing? If it were valve springs, you should float the valve at higher RPM. Floating valves, get swallowed.
From your description, I've heard exactly the same noise on older cars from the dust shield on the bellhousing being loose. I'm embarrased to admit, I'm unfamiliar with the V's set up.

DownSouthV
10-14-08, 08:14 PM
The title pretty much says it all- I have an absolutely disgusting sounding rattle/buzz coming from somewhere under the car when either letting off the gas in gear or pressing the clutch to shift. It's definitely tied to RPMs, and much more noticeable at higher revs.

If I had to guess, it sounds valvetrain related. It's always been there, but has been downright terrible since adding the headers a year ago (since the stainless acts like an echo chamber vs. the cast iron manifolds). I'm hoping I'm wrong, but running out of ideas. My Corsa is welded so it's not a leak, I've changed header gaskets three times and smoke tested those for leaks, and I even cut out the Corsa mufflers and replaced them with Magnaflows- still sounds like a big can of rattly ass when I let off it. It's at the point now where I can't even enjoy a drive with the windows down.

Sugestions? Anyone else had the problem and cured it? Commence speculation!


I have the same exact problem... and as with you it just started when i added my headers about 3 weeks ago. The sh!t drives me crazy driving around town. I hate even getting into the 4-5k rpm range unless im WOT due to the horrid noise. I was going to cut my mufflers out too but i may hold off on that due to you tryin it and not fixing it. I may take it tot he shop this weekend see whats up.

The Tony Show
10-14-08, 08:40 PM
We need to coordinate our search so we're not both chasing the same things. We should be able to narrow it down and kill it if we share our findings.

Just to clarify, I've had the noise since before the headers, but the headers made it 10x worse.

DownSouthV
10-14-08, 08:58 PM
It is possible mine did it before the header install and i never noticed it, however i notice it now for sure lol. I will let you know what i find out... ive done like you... pulled the gaskets off...replaced them... pulled the magnaflows off...checked for holes/broken welds and even re-welded some areas just to be safe. None of my efforts have done anything to minimize the terrible noise tho. The amount of times ive changed gaskets and dropped my exhaust really makes me wanna cry :banghead:.

rand49er
10-14-08, 09:02 PM
If you were to make a list of the usual suspects in order of priority, it would start with valve springs (or valve spring).

I don't know if there's a better way than popping the hood, remove the garbage can lid, unbolt the coil sets, remove the valve covers, and look things over. Next, do a good visual inspection of each and every spring. Since a few others here have had broken valve springs, there's a possibility that it may have happened to you, too. Springs that just got produced a bit too brittle ... it happens.

Anyway, that's my $0.02. :alchi:

The Tony Show
10-14-08, 09:08 PM
Thanks, Randy. :thumbsup:

My tech was too busy to get a scope on it today, but will tomorrow. I'm hoping it's something external (like a pulley) so I don't have to pull the valve covers, but if it does turn out to be a spring that's just an excuse for swapping in some Patriot Golds while I'm in there. :lildevil:

DownSouthV
10-15-08, 01:11 AM
free bumb