Flapping diaphragm vibrating tin like sound starting at 1800 rpm's?
 

I have been hearing a clapping like diaphragm vibrating tinny-tin like sound starting at around 1800 rpm's and up, you know like that wind-up monkey toy that claps the two brass plates together.

It's consistency is easily predictable and repeatable. I have a hunch that it has something to do with the turbo because as I understand the turbo starts increasing boost at around 1800 rpm's. I have had the walnut blasting done and the timing chain components replaced, does anybody know what this sound is? Do all MCS have this sound?

Much appreciated!

Systemlord.

Do I need to replace the spring in the blow off valve? what could be making that noise when boost starts to begin kicking in?

Any help appreciated.

Waste Gate.... Getting loose on its' mounting .

my 2 ¢
Good luck!
E.

I have learned that the MCS don't have wastegates, instead have blow-off valves that relieve the pressures during deceleration. How quickly the blow-off valves recovers from releasing the pressure and then repressurization for boost is what concerns me. When I go from 2nd gear and shift into 3rd gear when WOT is when I'm getting multiple misfires periodically, I think that tinny sound is what's also responsible for periodic misfires.

If somebody could chime in here that would be great! :)

MCS engines do use a waste gate for the turbine side of the system; The waste gate moves to open or closed to allow exhaust gasses to either bypass or turn the turbine.. It is a required part on a turbo charged engine so far as I know.
On the clean side of the system , there is either a B.O.V. or a diverter valve. The B.O.V. or diverter valve are 2 methods for keeping the compressor moving as fast as possible between shifts by dumping compressed air either to atmosphere (B.O.V.) or to the front of the compressor (diverter vakve). I gather this keeps the compressor from stalling / stopping or overworking when the throttle is closed and there is no where for the compressed air to go when between gears.
I know the N 18 engine has a diverter valve; Your N 14 on the other hand ,I am not sure.

So if I get it right:. You have the monkey with cymbals & a misfire at WOT between 2nd & 3rd?
Any codes? CEL?
E.

No the monkey with cymbals only can be heard at 1800-2000 rpm's, then it goes quiet. The misfires happen well above 2000 rpms, mostly 3000+ rpm's. The misfires don't happen enough to where the dealer can actually witness or diagnosis the problem and with no codes or cells their not very helpful.

You would think that when getting multiple misfires you should get some kind of code or cell. It happens sometimes but only once did it get so bad that there was almost complete power loss and still no codes or cells. If the car had been doing 20 mph the car would have stalled and stopped.

It seems the only way the dealer is going to know something is wrong is when I have cracked pistons. :-(

I would still argue that the cymbal sound is from the waste gate. As the waste gate just comes off the closed stop, you are maybe hearing the flapper rattle against the housing.

Another thought is to have a look at your exhaust heat shields. On my Hondas they were a continuous battle - chase the rattle!

This is still only a 2 ¢ bit of advice given from 1000'S of KM away! :)

The miss fire is beyond me - it might be linked to the cymbal noises but I dont pretend to know how...

this is an old thread but, systemlord, did you ever get this figured out? i think i have the same noise you're describing and am looking for info on fixing it. thanks.

I have been told it's either the vacuum valve that operates the waste-gate or the waste-gate itself, I believe it's the vacuum valve because the moment it starts to actuates around 1800 RPM's in second gear it makes a flapping light tin noise. Actually for a time the noise all but disappeared, then came back. Back when we had EGR valves made of rubber and lightweight alloys I remember the sound was the same as I'm hearing now. I never hear it in any other gear, when I first bought the car I thought it was pinging. If it were the waste-gate causing problems I would be getting the boost levels I'm getting, Dash Command shows up to 14.4-15 psi, Torque shows 12-13.5 psi. Not bad for an 07 MCS, recently had valves walnut blasted.

When I get the money I'd like to replace the turbo along with the turbo feed line and do it all at once.

Hmmm, alright. I Just ordered the WMW diverter valve, I have no interest in making more than stock psi, and will check the waste gate line and check that its actuator is mounted securely when I install the new diverter valve. Thanks.

Those are peak boost levels not actual boost levels, actual levels are closer to 12.5 at most.

Waste gate rattle is my guess.

My '09 MCS has this same tinny buzz starting at 3K when accelerating for the first few minutes. Some days it's fine. Recently I've notice it briefly between shifts too. Sounds like loose baffles in the muffler or heat shields more than monkey cymbals though.

Any downside to leaving it alone? No codes, runs great after a de-carbon at 60K mites.

It seems like my waste-gate rattle (only in 3nd gear) is gone for the most part after I started driving it harder. However sometimes (rarely) it comes back but only for a little while and goes away as fast as it appeared, the first 2.5 years of owning the car it happened all the time 24/7. I checked all my bolts for the heat shielding around the catted downpipe and all were secure. I wonder if it could be the pressure converter having something bounce around inside like a whistle as it sounds very similar.

Mine used to happen at low 3rd gear and nowhere else in the rpm range, I also had knocking only in 3rd gear bewteen 2800-3200 rpms under light, medium throttle. I wonder if...?