Mercedes CLK Diesel Engine Power Loss Whistling Noise

My 2005 Mercedes CLK diesel is playing up and I'm hoping someone can point me in the right direction. I'm getting a check engine light and seriously reduced engine power. Feels like I'm towing a house. Engine response is terrible, and it even stalled on me a couple of times when idling. Fuel consumption has definitely gone up too. I've also noticed a whistling noise, which turns into a loud hissing when I try to accelerate. I've read a bit online, and it sounds like it could be something to do with the boost pressure system. Could a defect in the wastegate valve cause all these problems? I have checked the MAP sensor, and it seems okay. I cleaned the throttle body as well, but no change. Any ideas before I start chasing ghosts around the turbocharger?

4 comment(s)

That does sound unpleasant. I had a somewhat similar experience with my old Vauxhall Astra – a petrol one, mind you. The symptoms weren't identical, but the lack of power and the strange noises were certainly there. In my case, it turned out to be a faulty diverter valve, which is similar to a wastegate. It was affecting the boost pressure. Is your wastegate electronically controlled or vacuum-operated?

That's interesting. I'm not entirely sure if the wastegate is electronically controlled or vacuum-operated to be honest. Is there an easy way to tell? And did your Astra also have issues with stalling and increased fuel consumption?

Yes, the stalling and fuel consumption were definitely part of the package with my Astra. As for checking the wastegate, look for an electrical connector going to it. If it has one, it's likely electronically controlled. If it only has a vacuum hose, then it's vacuum-operated. Honestly, with all those symptoms, I would recommend a proper diagnostic check at a workshop. It could save you a lot of time and money in the long run.

Thanks for the advice. I took it to a local garage, and they confirmed it was indeed a problem with the wastegate valve. The total repair cost came to 860€ including parts and labour. Runs like a dream now!

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