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Discussion Starter #1
Hi guys, Desperately looking for some expert advice on a problem im having! So basically, im thinking what i can hear is a police siren noise coming from my turbos. Gets louder when engine is warm and only audible under acceleration. NOT when idle. You hear it before gear change and also after. Its very loud. NO loss in power. No loss in MPG.

sounds alot like this:

Had a few people tell me it sounds like turbo issue, so took it to garage. Heres what i had done:

Breather pipe replacement
Small turbo refurbished
Oil feed pipe
Oil return pipe
New gaskets
Seals
Oil change
Oil filter

turbo refurb company said this: On inspection of your turbocharger we found a build up of carbon around the piston ring area of the shaft which had caused the shaft to partially seize.

prayed and hoped this would fix..
But it didnt. Still the same as before.

they couldnt find what was causing the noise. But they done a code check and these threw up:

4BD7 - engine mount activation
480A - particulate filter system

but, NO fault lights on dash. so im stumped. Iv booked it in to have a fault find at BMW next week. But i honestly cant see what they’ll find.

is it the larger turbo? Is it the DPF? Is it a hole in the exhaust?
Some knowledge and advice on this would be very much appreciated
 

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Did they check boost hoses for leaks?

Regarding that DPF code did they check exhaust back pressure with diagnostics?
 

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It’s definitely turbo related for sure. The code showing indicates the back pressure in the dpf is too high. Unfortunately it will not mow regenerate with that code logged. It needs to be cleared preferably whilst driving until the regen kicks in. As said in the other reply it would be useful to check for any other codes and also confirm that the engine is getting up to temperature as again this will stop a regen. The siren noise does not sound excessive and could be a leaking seal on the pressurised side. It is not unusual not too have an engine light with the codes you have. Did the turbo refurb garage give any comment on the condition of the big turbo and did the work on the smaller turbo make any noticeable difference?
Cheers
Jim
 

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Discussion Starter #5
It’s definitely turbo related for sure. The code showing indicates the back pressure in the dpf is too high. Unfortunately it will not mow regenerate with that code logged. It needs to be cleared preferably whilst driving until the regen kicks in. As said in the other reply it would be useful to check for any other codes and also confirm that the engine is getting up to temperature as again this will stop a regen. The siren noise does not sound excessive and could be a leaking seal on the pressurised side. It is not unusual not too have an engine light with the codes you have. Did the turbo refurb garage give any comment on the condition of the big turbo and did the work on the smaller turbo make any noticeable difference?
Cheers
Jim
Not very helpful garage really, they did a great job on the work they did but unfortunately did not look into the issue further or give me anymore info than what iv already mentioned. Its going into BMW on monday to diagnose issue. Just done a video for you guys so you can see exactly how it sounds. Will upload. Thanks
 

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That’s interesting as on the video the siren starts to kick in around 2750 revs and this is the point that the larger turbo starts to take over from the smaller one so could possibly be the larger turbo is the issue. Good luck on Monday.
Cheers
Jim
 

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Discussion Starter #7
That’s interesting as on the video the siren starts to kick in around 2750 revs and this is the point that the larger turbo starts to take over from the smaller one so could possibly be the larger turbo is the issue. Good luck on Monday.
Cheers
Jim
Ahh okay that’s interesting, i didnt realise that was the takeover point
 

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Discussion Starter #8
Just to give you guys an update.. took it to BMW this morning. Took it for test drive with the lead technician. He advised me that it’s not a boost leak. Its not an issue with the DPF. It is 100% an issue with the larger turbo. Top bloke, Didnt even charge me for his time. Advised me that by refurbishing the larger turbo he would bet his life on it fixing the issue. And understood the cost implications with BMW and actually told me to go get it done by an indi specialist for a fraction of the price. He said that 99% of the time its a small turbo issue. Just my luck that its the larger one! Typical!
 

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That’s good you have an answer now. Thankfully changing a turbo is not as expensive as people think. Essex turbos have a good reputation for replacement turbos.
Cheers
Jim
 
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