My car is a 2009 XKR with active exhaust. My problem is the valve appears to be flapping loose as the car is driven at a steady pace. It used to be loud on hard acceleration but quiet when cruising. It now sounds like a rapid (imagine someone speaking while rapidly placing one's hand off and on their mouth). Any suggestions on where to look to stop the flapping?

 

The vacuum-operated valves are on the sides of the rear muffler box, controlling flow through the outer pipes that bypass the muffler. They're powered by a vacuum pump & reservoir, and operated by a solenoid, all of which are in the LH rear wheel arch (behind the plastic arch liner).

It's possible one of the vacuum lines is damaged & leaking, so the system doesn't have enough 'suck' to pull the valves shut properly against the springs that hold them open by default. Or the vacuum pump may be on its way out. I'd have a good look under the car around those valves & check the vacuum lines, and also whip the wheel & arch cover off and take a look at the pump assembly and associated plumbing.

Obligatory dumb warning: make sure the car is securely supported before you start messing about underneath!

 

If you have a small vacuum hand pump just pull the line on the mushroom can on the outside exhaust pipe and pump it up and see if it holds vacuum. If so then you need to trace the vac lines back to the can and solenoid.

 

Or just remove fuse 19 - my car is still quiet on cruising even with the fuse removed and the valves open all the time, it's just a little bit louder on acceleration from lower revs.

 

And we love it that way!! So do a lot of people that hear the cars growl.

 

I pulled fuse 19. It still fluttered as it appears there isn't enough strength to hold against the exhaust pressure. Thanks for the suggestion.

 

With Fuse 19 out, the only force operating is the spring that's supposed to hold the valve open. Perhaps you have a busted spring.

There aren't any instructions in the 4.2 manual for removing the valve, but there are in the 5.0 manual. I'm not sure if that means the valve isn't serviceable on the 4.2, or whether they just missed that bit out of the manual.

 

teddy, i had exhaust issues with my 07 xkr, It is fitted with a milltek full system and the exhaust tubes are not needed just pluged up.Then one day the exhaust just sounded different, the lovely deep throat sound was gone , left with normal xkr growel. To my regreat it was a cat that was gone. Not to worry you but maybe a cause if your system sounds different