Why has my dump valve started to sound like a VTA blow off valve? I've got a totally stock car and stock factory dump valve but when I lift off the gas it has started to sound like a vent to atmosphere type. It used to be silent but recently it's started to get louder.
Car is a 99 uk turbo.

 

Maybe it's just old n knackered I had a forge recirc one and it was solid

 

As above could be a knackered diaphragm, my focus st one went then sounded like a atmospheric one.

 

Ok cheers for the comments. It is on 150,000 miles! I didn't think there was much to go wrong except a spring.
What's that forge one like? Silent like the standard recirc?

 

First, check the obvious.... See if the recirc hose hasn't worked loose (at either end).

 

I have the Impreza MY97/98 Forge recirc. on my STi 5 (but running a FMIC). I get a very rapid, cool-sounding compressor stall noise upon lift off (coming out of mid/high boost)... I'm guessing the air is exiting the open cone filer, hence the noise... Although, it's not intrusive, or BOV-esque #whooshy# lol -- I dig the sound.

If you still have the OEM panel filter/closed airbox assembly though, I'm guessing it'll be quieter... Maybe barely audible...?

 

I can't see any obvious signs of damage, I might blank it off and see if that changes anything. I also think I'm also getting a boost leak as there is some whistling as the turbo comes on boost and the car isn't as smooth as it should be when accelerating.
Cone filters un leash all those cool turbo sounds!

 

In that case, check all the hoses/clips/fastenings from the turbo outlet, through to the TMIC, and onto the throttle body. Also check the gasket and mounting bolts for the DV to the TMIC.

Remove everything, check and rectify as necessary...

 

Yep all good advice cheers, I'll try that this week.
Gonna order a new gasket anyway as they're very cheap.

 

Totally.