2007 2.7 tdi aut. - humming, resonating noise on low rpms when cold

**Crasher** · 05-11-2015,02:25 PM

If your car has the fuel filter with the plastic check valve, I have had quite a few of these humm.

**niall campbell** · 05-11-2015,07:52 PM

I wonder if its the alternator clutch on its way out ?

If you look at the scan, it does mention battery regulator etc on it

Can you disconnect the belt on the alternator and run the car ?

If it is the alternator, then replace like for like ........................ don't get a Lucas one as it wont talk to the car ............... I had major problems with this

**MarkTM** · 06-11-2015,10:53 AM

Originally Posted by niall campbell

If it is the alternator, then replace like for like ........................ don't get a Lucas one as it wont talk to the car ............... I had major problems with this

If it is the alternator, just get the existing one rebuilt/refurbed, the aternator can be taken off without removing the front of the car (from underneath), I paid £35 for the removal/install and £38 to have the existing alternator repaired.

Far cheaper than a new one and trouble free for the last year. Local battery centre or garage should be able to advise who does refurbs in your area.

**Crasher** · 06-11-2015,06:00 PM

The 2007 All Road with a BPP engine uses either a Bosch 0 121 715 120 (VAG 059 903 017) or Valeo 43751 (VAG 059 903 015 R) and as far as I can tell, neither of these has a free-wheel pulley. If I were to fit a new unit on this car the only one I would recommend is the Bosch 0 986 080 090 exchange unit.

**cozmo** · 20-01-2016,03:09 PM

For some reason I didn't get notifications for the last posts (all the way back in November 2015), so I stumbled upon my own thread here after googling "audi low rpm hum" :-)
Goes to say - I have not resolved this issue. It's been cold has h##ll here in Norway the last month, so not so cosy to work on the car. However, I got around to changing the glow plugs during the christmas holiday, and man that was needed. 5 out of 6 was totally gone. No wonder there were problems starting i -20 degress celsius

Anyway, thanks for the tips regarding the alternator and fuel filter. As soon as the temperature climbs closer to zero, I'll look into this. Is the alternator on a separate belt? I need to drive the car to provoke the humming, so if detaching alternator belt also means stopping stuff like water pump - that makes things a little more complicated...

**cozmo** · 21-01-2016,12:48 PM

Update: I booked the Audi in at an Audi specialist shop nearby on Monday. I simply haven't got the time or energy to dig into this myself right now. Our other car, an old Saab 9-3, steals all my energy on its everlasting need for repairs :S
So, guess we'll see if they can figure it out. I cannot stop thinking it has something to do with air/exhaust escaping on its way in or out.

**cozmo** · 25-01-2016,10:35 AM

Update again: So i brought the car to the Audi shop this morning. Problem is this phenomena with the humming and resonating noise is partly intermittent. And typically today it was barely noticeble at all.

But the mechanic took the car for a spin and did a quick vcds scan while I waited. But as i suspected - they couldn't find anything in particular.

So I guess I'll live with it for now and see if it gets worse...

**cozmo** · 23-02-2016,08:22 AM

Well, is has most definately gotten worse. Today it was "brooming" all the way to work (very cold this morning). But If I book a new time at the local indie, I'll bet it decides to be quiet at that particular day anyhow, so no use.

I think my time as an Audi owner is over. Never had a car with so much annoyances and stuff going wrong over such a short period of time. Guess I'll wait until spring and warm weather and pass it along to a new owner

**niall campbell** · 23-02-2016,12:55 PM

But all that has gone wrong is the glow plugs . I would expect anything over 45,000 miles to do this as expected. I was always told to wait 2 seconds after glow plug light goes out to start car, the glow plugs are still heating up & waiting means the glow plugs life is extended also, most people don't bother ................. especially in summer

Can you do me a favour and look at your Power Steering fluid level please. There are owners who have complained about this , its usually mineral oil, which can be a bit funny in cold weather. This might be low , which made a noise in cold weather in my car .......................... but since top up its fine. Mine hasn't leaked since & baffled where it went !!

Any moisture that has gotten into the oil , will freeze as we know, maybe its due changing ?

Canadian car owners also know to fit good quality auxillary / fan belts to cars, as these will make noises in cold weather.

**cozmo** · 23-02-2016,01:28 PM

I have no problem replacing glow plugs, or other normal wear and tear parts like brakes, bulbs, oil and other servicable parts.

What I hate is unknown noises, rattling or other obscure faults like cooling hoses cracking etc. I guess a jap is my next car, however - I hate the cheap, rattly plastic experience they come equipped with.

My servo oil is at correct level by the way.
I have a strong feeling that this "brrooom" on 1200 rpms is related to air somehow. Either air-in, or air out.

Aren't the swirl flaps activated at round this rpm? According to the mechanic at my indie, the 2.7/3.0 tdis most common faults are related to the swirl flaps failing due to carbon build up inside.