Hello,

I recently applied caps to delete the rear PCV hose on my 2007 MCS in hopes of preventing carbon buildup.

The peculiar thing is that when I re-installed my DOS intake and started the car up, I'm hearing a very peculiar low resonance noise from the intake side of the engine while idling. (wohm, wohm, wohm, wohm, wohm, wohm...)

I checked to see if there were any loose intake components that may be causing this sound, and there doesn't seem to be any evidence of such. The noise does not alter or decrease/increase with RPM, and the engine otherwise seems to be running fine.

It sounds like it may be a vacuum or air related issue, as it is clearly being made audible through the cone filter behind of the firewall of the DOS intake.

Could the PCV hose delete have caused this issue? Has anyone else experienced this sound?

The timing and timing components of the engine all sound regular.

My clutch release bearing was on its way out and has been making noise for a few months, but this sound is otherwise heard with clutch engaged or not. Am I hearing an engine related condition?

I'll be bringing the car into my mechanic on Tuesday but would love to hear some opinions or suggestions until then. Thank you.

 

Just out of curiosity, when did you the PCV delete did you put one on each end of the connection where the PCV hose was located at?

My understanding is that if you add a BSH boost tap in line then you only need one. But if you do the PCV delete then you need 2. One on each end.

Maybe I am wrong..........

 

I certainly did. I also reinspected my work to ensure both caps were properly fitted.

As mentioned above, it's very peculiar because the sound is audible inside and outside the vehicle, but engine operation is normal. I've noticed no loss of power, no odd idling, no strange noises from other areas within the engine compartment or areas of the vehicle.

I'm just wondering if there are any other engine conditions which would potentially create a sound to this effect.

It appeared right after the pcv hose delete, and I otherwise keep a close ear on the engine regularly. I've not installed a catch can yet on the remaining pcv line yet, but doubt it would eliminate the issue.

Are there any other probable scenarios to consider?

 

It's the full load breather valve opening and closing it is nothing to worry about the only reason you can even hear it is because you have a DOS intake.