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Peugeot 306 hdi - Help finding a whistle in the engine bay - scfc_151

I have an anoying whistle in the engine bay. I took it to my local french car specialist who located it near the egr valve at the drivers side bulkhead but cant pinpoint it.

Ive been told it could possibly be to do with the fuel rail and that some people think changing the fuel filter housing (bad one way valve) would help.

I cant see how if it sounds like its near the egr.

Anybody have any ideas what it could be? the mechanic reckons it sounds like an electrical whistling.

Peugeot 306 hdi - Help finding a whistle in the engine bay - bursty

Has it recently had a new exhaust fitted? I had a similar problem several years ago with a 306 after a new exhaust was fitted. For weeks they told me that it was my turbo and later they discovered that the exhaust had not been sealed properly and that was making the whistling noise.

Peugeot 306 hdi - Help finding a whistle in the engine bay - scfc_151

Thanks for the reply but the exhaust hasnt been touched. I thought about that though.

Ive recently had a fuel pressure regulator fitted and an air flow meter because of some fault codes that came up on the diagnostic.

Since then the car feels more powerful, smoother and has less smoke out of the exhaust under load.

However now this whistle is there and it sounds slightly throaty under acceleration. A couple of people have mentioned the fuel rail could be making this noise or changing the fuel filter housing may help.

The grumbling sound under acceleration reminds me of when the throttle position sensor needed replacing a while ago. I presume this was due to underfueling so im wondering if its upset something by replacing the fuel pressure regulator and air flow meter?