I am reluctantly starting a new thread on exhaust valves ( there a quit a few already) but I can’t seem to find the answer to an easy(?) question.

I have a 2017 S coupe which I believe uses manifold pressure to work the exhaust valves, but you can’t see if they are open or shut through the exhaust system.(6 cyl)

They seem to be in quiet mode always, and the pistons on the valves appear to be all the way in?

If there is no vacuum on the system, they should be loud, and the pistons extracted?( or compressed in?)

Thanks for your input!

 

Ok, I just checked mine. The valve is held open by a spring, with the piston extended. I can push the piston in (some) to partially close the valve (it’s a pretty strong spring.)

 

Thanks for your reply!
So my pistons are compressed(in) that means the valves are closed and quiet.
They should be out when the car isn’t running, since there isn’t a vacuum?

 

Correct. This is why starts are always loud. It has to build up the vacuum before the valves close.

 

Any thoughts on why they closed without vacuum?

 

If you got the car used, maybe the previous owner defeated the valves somehow? Use pliers to try pulling the piston shaft out, but keep your fingers clear, there should be a pretty strong spring trying to push it out. I was able to reach one of the valves with my car on the ground.

 

I’ve had the car since 2021 and the valves have worked up until 2 weeks ago.

 

Starting on p. 4805, the Workshop Manual has a good description of how the active exhaust system operates.
https://www.dropbox.com/scl/fi/o6d1x...=07j1wjnv&dl=0

 

What has been done the car at that time?

 

Just went back to my mechanic to check position of exhaust valves-
in quiet mode the pistons are in, switching to dynamic they pull out
So it should change the sound, but no difference in either position?!
We can only guess that the valve mechanisms are broken inside?
Appreciate any advice or opinions
thanks again!

 

According to this picture, you should be able to easily run an endoscope up the pipe to look at the valves on the inside, though the endoscope might get sooty.

 

Great idea! Thank you
if they are broken I can just cut them out and put in a small straight pipe, but will be loud always

 

Looks like I’m going to cut the valves out this Wednesday. Any advice on how to handle the vacuum line?
Should we cap it? Will it affect engine performance if left open?
Thanks again for your input!

 

I would NEVER leave a vacuum line 'open'.

Cap it!

 

The vacuum lines connect at the solenoid switch before the exhaust valves.
If the switch is off, as in dynamic mode,that essentially is capping the line?
Vacuum only works on quiet mode correct?
please correct me if I’m misinformed
thanks!

 

Vacuum is always present with engine running and with dynamic mode at idle, I bet you would probably not notice a difference in sound.
Best way to test is to open rear hatch and take off in both normal mode and dynamic and see if you hear a difference and when I say take off, I mean tire spinning launch.