I have a 2.0 turbo diesel passat - just 3 yrs old. First diesel I have had. Its quite rattley especially at tickover and takes maybe 2 minutes to quieten down. Is this characteristic?

Personally I would NOT drive it. Get the turbo repaired/replaced! Modern vehicles have engine sensors that will cause even more running problems as they aren't detecting the turbo doing it's job.
Diesels will run without a turbo but they are usually ridiculously slow and really really struggle to accelerate.This is especially true on smaller diesel engines like those you get in cars and smaller vehicles. I had a turbo fail on a 2.0 litre diesel engine and with my foot hard down it took me well over a minute to hit 50mph, and that was before I got to any hills.

The first video should help

https://www.google.com/search?q=2004+VW+Passat+2.0L.+Turbo%2C+air+temperature+sensor

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Best going to a nissan forum to ask this
Truck SUV Nissan Forum
Nissan Trucks Forum

diesel engine version ,to be honest i would need my dirty grubby hands under the bonnet and listen to it when cold to have the slightest idea as to what the problem could be.Owing to the complexity of modern engines unlike a good old bedford TK or a garner the faults as you appreciate can be quite expensive to correct a silly fault or just a quick bit or hose replacement will suffice ,try reading the OBDII to see if any sensors are throwing a code up if no codes then start from cold and use the moniter status and check the readings of the temperature sensors ? failing which run it into a bosch diesel garage who have all the fancy software to check it out because unlike a good old ford D series where i could adjust the injection pump with the engine running to regulate the fuel output and reset the injectors on a simple pump with a glass dome iam now consigned to classic car repair or becomeing a macdonalds sweeper uppere

Its quite an old vehicle so most probably turbo has gone. Go to any good mechanic and he will be able to diagnose the issue in your turbo by taking it apart. Most of the time some normal servicing of turbo that require some change of components in it makes the turbo as good as new one.

PLEASE DO NOT add any oil to the fuel,use redexe/wynns diesel additive to clean the lines/injectors/turbo vanes,but burnt oil will stick to the turbo vanes and could cause failure.....just use 10/40 semi synthetic oil as normal and change regularly.also let the car tickover for a min or two after a HOT run....

A bearing going bad. Do you follow turbo shut down procedures? If you don't have time to do this then my suggestion is installing a turbo timer to do this automatically. When you drive the car specially a high speed and need to shut down the engine is the worse thing you can do to your turbo. The impeller spins double the speed of sound and takes quite a while to slow down specially when you shut down the engine. At the same time it is shut down, oil pressure is no longer provided by the oil pump and cooking from extremely hot turbo assembly. The end product is oil carbonizing and clogging moving parts. The term is called coking. A turbo timer will keep your engine running when you remove the key from ignition and lock the vehicle for a programmable amount of time. This will help the turbo to spin dow while lowering the temperature critical for a longer servie life of your turbo charger.

Try the airmass meter and air intake pipe,very common cause for lackof power.

Hi,
This is the second Vw I have responded to in a fortnight.
Your lack of power I presume always happens when the glow plug light illuminates?
This is because it is causing over combustion to vaporised diesel, I would be looking in the Glow plug timer and relay, as for Turbo lag, I run a E34 6 cyl Bmw Diesel and the Turbo only kicks in around 2,500ish so maybe yours is a little tired or in need of a check up?
Hope this helped,
Paul 'W'
Onyer~EDson(:0) {#><U.K.
Please remember to rate my effort!

Generally it is not recommended using parts either that the ones designed for same model, however some Passat engine connects same way as Golf. You need to know the Passat engine year and verify engine mounting procedure and connections positions. Getting the two Haynes manuals for the two VW models can help you to compare.