RS4 Exhaust Valve/flap

[MCPCJC]

Hi Everyone
I'd like to pick your brains, my B7 RS4 one exhaust valve opens and closes as it should but the drivers side will not open when the sport button is pressed, it just stays closed. Am I correct in thinking that it is held closed by the vacuum system ? So when the car is off it should be open, then close when you start the car and open again when the sport button is pressed. The valve does seem stiff compared to the other side which seems to spring back if you move it manually.
Thanks

[Dr G]

They get stuck (coked up with carbon deposits).

Blast it with isopropanol (brake cleaner) as best you can then it's a case of manually manipulating it and adding some spray lube until it frees up. Keep doing this until it opens and closes nicely. A regular clean and squirt of lube will keep them working properly, in extreme cases and if left stuck for ages it can mean a new backbox.

[MCPCJC]

Ok thanks will give this a go.

[MCPCJC]

Hi
Tried this, managed to loosen the valve up but it still won't open. It's as though it wont spring back to the open position like the other side.
I presume the vacuum system is working as the valve closes when you start the car.
Any suggestions?

[Dr G]

When our workshop clean/free these it's a slow process of repeatedly moving, cleaning, and lubricating the flap. We have also replaced a small number that were too far gone and do as you describe (simply won't work despite careful cleaning).

I can't suggest anything further than the elbow grease already mentioned, sorry

[MCPCJC]

Ok thanks for your help.

[MCPCJC]

Can I just ask, is it a case of replacing the valve or do I need a complete back box?

[Escort3500]

I think it's the whole back box from memory. But you can get them cheaply s/h ( make sure you get one that works!)

I didn't bother with mine, just removed the rubber pipe from the valve, put a screw into the end of the pipe and a cable tie and run it with the valves open all the time.

[MCPCJC]

Thanks, I think I'll do this.