Odd Sound after car is warm

[pixelhaus]

the other day my engine began making a pretty loud 'fluttering/clanking' sound after running for a while. it isn't very apparent when first started, but once warm it becomes very loud. upon throttle it gets louder. more of a fluttering sound than a clanking sound, but somewhere in between the two, almost like an extremely exaggerated valve clatter.

any ideas? suggestions on what to test?

thanks everyone.

 

[Commander]

If you have a standard tranny NSX try pushing in and holding the clutch pedal down. If the flutter sound goes away than it's probably your clutch throw out bearing, when it gets worn they can make noice, also the hotter they get the noise increases. If no change than at least it's not your clutch but unfortunitely someone else will have to give you ideas since it's most likely an engine issue.

 

[chado]

the other day my engine began making a pretty loud 'fluttering/clanking' sound after running for a while. it isn't very apparent when first started, but once warm it becomes very loud. upon throttle it gets louder. more of a fluttering sound than a clanking sound, but somewhere in between the two, almost like an extremely exaggerated valve clatter.

any ideas? suggestions on what to test?

thanks everyone.

I hear this exact noise that your describing and I had both Ramon at Niguel Motors and the guys at Autowave listen to it. I had Ramon pull of the intake manifold and make sure there wasn't anything loose that shouldn't be and that would lead to catastrophic damage. Of course there wasn't and when the guys at Autowave heard it they said it sounded just like a little bit of chatter from the butterfly valves flapping where some of the (teflon?) coating had been worn down..
No harm no foul... still running strong. :smile::wink:

 

[pixelhaus]

thanks for the responses.
i think the butterfly would be wishful thinking in this case.
definitely sounds more internal than that and a lot louder.

 

[davidf]

Can you make a decent sound clip?

 

[pixelhaus]

will do, i'm away right now, but will do when i return.

thanks

 

[(NSX REY)]

Pixelhaus,
Here is my suggestion on the sounds you described. Does it sound like it is coming from the bottom end (Crank)? With the car running disconnect each coil pack wire one at a time replacing as you move on to the next. You can manually rev the motor pushing the throttle cable. If the sound goes away when you disconnect the wire, I would suspect a bad Rod Bearing. I hope I’m wrong but it’s a good place to begin your trouble shooting. Until you know for sure it isn’t a bearing I wouldn’t drive the car because your repair cost will shoot through the roof if you do more damage.
Good luck!

 

[chado]

thanks for the responses.
i think the butterfly would be wishful thinking in this case.
definitely sounds more internal than that and a lot louder.

Trust me I said the same thing! Remember these engines are pretty noise/loud as it is. DO this.. at idle rev it to between 2k-3.5k and hold it there. See if you hear it more distinctly and louder. Then rev higher and you will hear almost go away at 4k and up or at least not with the same nasty sounding chatter..
I thought the same thing you did and when I first took it in everyone (2 nsx techs and owners) said it sounded like it was doing damage to the engine. Shane at autowave immedietly explained the noise...

 

[sicarius82]

bad Rod Bearing. I hope I’m wrong but it’s a good place to begin your trouble shooting. Until you know for sure it isn’t a bearing I wouldn’t drive the car because your repair cost will shoot through the roof if you do more damage.

It would suck to be a bad rod bearing. At least it may give him the excuse he needs to build the bottom end...:biggrin:

 

[pixelhaus]

It would suck to be a bad rod bearing. At least it may give him the excuse he needs to build the bottom end...:biggrin:

well, it was actually 'rebuilt' twice within the last year (6 months to build each time), and i've only driven it maybe 4 hours total.

yes, that would really suck if it failed again.

 

[dynomike]

does the sound get louder when engine rpm is raised why was the engine rebuilt trice in a year?

 

[pixelhaus]

dyno mike, pm sent

 

[KrayziE RussiaN]

well, it was actually 'rebuilt' twice within the last year (6 months to build each time), and i've only driven it maybe 4 hours total.

yes, that would really suck if it failed again.

When the engine was "rebuilt", what exactly did they replace? Was it a bottow end or top end rebuild or both? Were all parts mic'd, especially in the areas that the bearings failed (eg. crankshaft, etc)? Are you running poweradders that would keep causing this type of damage? This definitely sounds like a "bearing" problem, since it gets louder when warmed up, this would make sense, since the oil gets thinner when warmed up.

 

[pixelhaus]

When the engine was "rebuilt", what exactly did they replace? Was it a bottow end or top end rebuild or both? Were all parts mic'd, especially in the areas that the bearings failed (eg. crankshaft, etc)? Are you running poweradders that would keep causing this type of damage? This definitely sounds like a "bearing" problem, since it gets louder when warmed up, this would make sense, since the oil gets thinner when warmed up.

Bearings do make the most sense.
FactorX did the build. full build (bottom end), sleeved, low comp pistons, etc... the car is turbo charged. it's a very, very, very long story, but first build failed and not sure if second build was done as thoroughly as it should have been done (bandaid repair?). well, i think it's pretty obvious considering this happened within hours of getting it back.
the story is long and painful, financially, physically and emotionally.