Can anyone outline the egr and wastegate circuit from the two electrovalves on the bulkhead for me (on a 2003 HDi 110)?
One of them (I think the left/offside) is making a chattering/pinging noise when the engine is turned off, lasts about a minute, but can be stopped by repeatedly pressing the brake pedal. It also chatters away to itself whilst driving but I'm not familiar with where the pipes go or how the braking circuit is involved.
Is this likely to be the valve itself or bunged up pipes? Can't find much info on it so I guess it's not all that common a problem.
I've never heard of this particular fault before on an HDi, but to me it sounds like there could be a fault with the solenoid valve itself. The brake servo, egr solenoid & wastegate solenoid all share the same vacuum pump on the HDi 110 (at least they do on my Xsara with the same engine as yours.) Thats likely why you can make it stop by repeatedly pressing the brake pedal with the engine off, by doing this you are exhausting the reserve of vacuum in the system.
Before you change the valve though, it could be worth testing the electrical supply to the solenoid valve just to make sure its not actually an electrical fault causing the valve to chatter with the engine off. As far as I know the valve shouldn't be getting any voltage with the engine turned off.
Thanks for your reply - I didn't realise they shared the same outlet from the vacuum pump!
I'll have a look at the supply as you suggest. It sounds rather like the solenoid is pulsing, bleeding off the remaining vacuum when the ignition is turned off, which as you say it shouldn't be able to do. I can also hear it quite a lot at low speeds. Will also try to check out the pipework. Everything is linked up (though I am assuming it to be in the correct order!) but I haven't checked for blockages yet.