Dump valve on 2001 A4 1,8 TS

Hi again,
Question this time on what might be causing a rapid clacking sound under accelerations around 1500-2000 rpm, especially when engine is hot. I am
beginning to suspect the dump (bypass) valve, since I've now heard that the valve can open and close rapidly, creating this kind of noise, if malfunctioning.
Anyone having any experience of this.
For those who know something about dump valves, what kinds of symptoms can a faulty valve cause?
Thanks, Robert
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More likely you have a bad waste gate actuator. When that goes bad you hear a rattle and your boost is very low. You can just barely see the wast gate actuator rod under the tubing. Put a small wodden stick in there (engine shut off) and try to move it. If it moves at all that is your problem.
The actuator and rod can be found for about $200 but the work to pull the turbo is enough to make it worth considering a new K03.
or ..
Better yet you might find this a good time to upgrade toa Ko4 and chip from APR.
Robert wrote:

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Tony wrote:

Tony, I haven't had the opportunity to try to move the actuator rod but I do know that I always get good boost, which is why I'm doubting that the wastegate (or the electromagnetic valve that sets up the vacuum that moves it) is the trouble.
Do you or anyone out there know if a faulty dump valve can cause this?
/Robert
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This isn't a symptom I noticed, but my 1.8T (2003 OEM valve) started to "chatter" when I let go of the throttle. (Accelerate *hard* and then really *let go* of the right pedal). It's not hard to pull out the DV and have a look: there's a simple test for one of the more popular non-OEM replacements described here:
http://www.forgemotorsport.com/valve_service.pdf
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