deilenberger

So - being of the paranoid persuasion, as all the other V8 owners - I'm super sensitive to engine noises.. particularly a "rap" sort of sound.

My '11 has had a tap/rap since the day I got it at around 48,000 miles. It now has 30,000 more miles on it, and has had the Variocam adjusters replaced as preventative maintenance (told you I'm paranoid).. so the engine was out, the heads removed and reworked, I looked at the cylinder bores (looked perfect), and all reassembled. The rap/tap was still there.

Since a few more reports of failed bores have been appearing lately, and I'm thinking of doing another trip to California next month with the CTT - I spent some quality time with my mechanic's stethoscope under the hood with the engine idling.

Probing around the coils/plugs - all sounds perfect. Probing around the valve covers - perfect. Probing down near the exhaust manifolds - perfect. Finally I started probing near the very front of the engine, bank-1. And I heard the tap/rap. I kept probing the engine cases, thinking the noise was coming from inside the engine. It suddenly got REALLY loud in the stethoscope.. and I realized the probe of the scope was resting against this - what I assume is a check-valve.

So I put my finger on it - and could feel a sharp tap in it. It's mounted in a rather elaborate rubber mount, so I'm guessing some noise from it is normal.

But - the question remains - whatzit?

Before I spend endless hours going through the 11,000 page manual - perhaps someone who knows what it is could enlighten me.

And perhaps someone else with a CTT could open their hood and see if theirs is making noise.

Since it's lasted this long I can't imagine it's anything actually serious - but if it's simple to make it stop making the tap/rap noise - I'm up for it.

The mystery device is circled in orange:




Whatzit?

deilenberger

After an hour or so with the service manual.. best I came up with is:




Not surprisingly - there is no overall diagram of the emissions system plumbing, so it's hard to confirm this. I can remember when a diagram was pasted inside the hood on cars, I don't see one on mine.

There have been no engine or emissions codes recorded - ever.

Puzzled.. rappa/tappa, rappa/tappa

Petza914

Since #3 has to do with tank ventilation and we know the other rhythmic sound we hear out of these motors is related to the pulses from the high pressure fuel pump, I'm betting it's a harmonic related to that and is probably nothing to be concerned about.

wkearney99

Is there ever actually an engine compartment noise that supports that notion?

Petza914

The only one I can think of is the tick, tick, tick of the fuel pump, but then again, maybe it's something else :/

deilenberger

It's really frustrating not having the emissions plumbing diagram. Mebbe I'll look on AllData - they usually condense the 11,000 pages of manual into something useful.

And would someone else with a CTT take a listen/feel of the check valve on yours? Please?...

deilenberger

Ah ha!! Found some info on AllData (continuing to look..)

Found a bit of info in the fuel tank ventilation system section:

My thinking is - that check valve may just open/close (making a click sound when it does) when the engine is at idle and there is basically 0 boost.. the turbo still is spinning, but not building pressure..

So - could someone with a CTT open your hood and listen?

Petza914

This is the system that fills our Driver's side intercoolers with condensed oil and why many have installed a catch can setup to condense this oil vapor somewhere other than in the intercooler. I bought a Mishimoto one to install once I get my Turbo S back with the upgraded FVD intercoolers.

AGARubberDuck

Don, I took a video of mine at idle for you. can't upload an MP4 so when I get back from lunch I'll pop it into YouTube and link it here.
The clattery noise this engine makes under the hood is not sexy, but I don't know if I'd describe it the way you are.

deilenberger

Thanks. Sounds a lot like mine. I'll have to video and upload it..

There we are:


I took the beauty cover off the throttle-body for the video - you can hear it a bit better (louder).. and I can actually feel it in the check-valve and the hose going to the throttle-body. If I wrap my hand around the check valve - it muffles the click.. which makes me think about some localized noise suppression material.

desmotesta

my wife's 958 GTS has a tap tap tap sound in cabin.. seems to be coming from engine bay

I can't hear it well with engine running (and hood open) but its audible (at times) in cabin.

I was told that it is Tank ventilation and is "normal".. take it for what its worth

In my case, the frequency of tap tap tap does not increase with higher revs.. it actually goes away as I rev the engine

deilenberger

Actually - that's the PVC system on the other side of the engine.. If you look at my video - to the right of the throttle-body is a big-*** (tech-term) check valve for that system. It's an interesting design.. if you disassemble it you destroy the connectors between components and you're supposed to replace it piece by piece. I *hit you not.. right in the manual and AllData.

deilenberger

Actually - I believe I've noticed that too.. have to get someone in the car to rev the engine a bit while I'm listening under the hood.

DaVinchy Vol

2011 ctt here

thank you for the thread, it eased my mind. Im currently in the midst of a cross country trip and started noticing a weird tapping sound in cabin at idle>1500 rpm. After u rev past 1500, the sound goes away, once idle settles, the sound comes back... was kind of freaking out.

up the volume. After i rev it, ull hear tapping come back after it settles at idle

RAudi Driver

I was going to say check valve as my BMW has that sound also. I have the same sound. Don't know if it's coming from the check valve. I always thought it was my turbo bearings and was just waiting for something to happen, but the car keeps pulling like freight train. Doesn't burn any oil and other than the slight sound, runs perfect. SA, says the sound is normal and they all make sounds.

When it starts to bother me, I get in the GT3 for a few and realize that the cayenne is quiet.

D, I'll check with my steth today.