Author Topic: Rattle / metallic noise from belt area. Present when cold at startup.  (Read 1289 times)

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  • dk Denmark
    Danmark
Hello everyone.

I just bought a used i30 1.6 crdi 180000km at the clock.

I have a noise / mechanical problem with the car.

When the engine is cold i get a weird rattle / metallic sliding noise from the belt / alternator area. This is only present when the car idles an goes away after 2-3 minutes og idling / driving.  Other times, the noise dos not appear.

So far, I have replaced -
the belt with a new original
The idler pulley
The tensioner pulley, but not the tensioner. It seems to be working fine.

The problem gets worse if I turn on the cars electric functions, like the rear heated window. I have tried stating the car without the belt, and the noise has not appeared.

I have read all the topics around about similar problems, but mine seems to be a little different, as it goes away, as soon as the engine gets hot. Using the air-conditioner makes no difference.

I will try and upload a short video of the problem.

I am leaning towards a bad alternator clutch pulley, but I am not sure, as the sound disappears after a little.

So, guys do you have any suggestions?
« Last Edit: July 25, 2018, 15:44:54 by Soegaard » »


  • i30 1.6 crdi 2009 90 hp.

:link: I30 rattle noise - YouTube


Link to a video with the sound / problem.
  • i30 1.6 crdi 2009 90 hp.

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  • au Australia
    Ipswich
Hello everyone.

I just bought a used i30 1.6 crdi 180000km at the clock.

I have noise / mechanical problem with the car.

When the engine is cold i get a weird rattle / metallic sliding noise from the belt / alternator area. This is only present when the car idles an goes away after 2-3 minutes og idling / driving.

So far, I have replaced -
the belt with a new original
The idler pulley
The tensioner pulley, but not the tensioner. It seems to be working fine.

The problem gets worse if I turn on the cars electric functions, like the rear heated window. I have tried stating the car without the belt, and the noise has not appeared.

I have read all the topics around about similar problems, but mine seems to be a little different, as it goes away, as soon as the engine gets hot. Using the air-conditioner makes no difference.

I will try and upload a short video of the problem.

I am leaning towards a bad alternator clutch pulley, but I am not sure, as the sound disappears after a little.

So, guys do you have any suggestions?
I was going to suggest maybe timing chain but if it's gone with the aux belt off then that sounds conclusive.

You could check the clutch pulley fairly quickly by removing the belt, then grab the alt pulleyy strat to turn it clockwise(normal direction) then sharply  change then direction to anti clockwise. Should be enough inertia to have the clutch pulley slip which is what it should be able to do it that direction. or if you can lock the internals of the alternator without damaging the windings then you could also trying turn that pulley in reverse.

Replacement, you need the correct splined tool to insert into the pulley and a impact gun. I did a thread on it a while back when I had one seized .
  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly

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  • Posts: 2,594
  • au Australia
    Ipswich
Ok, with that video, sounds like a bearing dry and maybe seizing momentarily. have you spun by hand any of the idler or tensioner pulleys, looking for stiffness, roughness , or rumbly sounds.

Check the clutch pulley but I'm thinking also it's one of the others or you may have more than one item on it's way out if all original.

Or you could just replace them as preventative, I find the plastic OEM idler is the first to go.

also should mention there's internal bearings in the alternator too, at this distance any of those could be suspect, sin by hand same applies you'll be looking for rumble, roughness or unusal resistance(binding)
  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly

Thank you for the quick reply.

At first, I also thought it was the timing chain, but I am leaning towards it being a belt related problem. but I am not sure. I have to do some more startups without the belt to rule out the chain.


When i jam a screwdriver in the alternator, it locks in one direction, and rotates in the other. The pulley wheel can move a little in and out. Is that normal? The pulley feels a little rough when spinning hard.
« Last Edit: July 25, 2018, 16:13:58 by Soegaard » »
  • i30 1.6 crdi 2009 90 hp.

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  • Posts: 2,594
  • au Australia
    Ipswich
Thank you for the quick reply.

At first, I also thought it was the timing chain, but I am leaning towards it being a belt related problem. but I am not sure. I have to do some more startups without the belt to rule out the chain.


When i jam a screwdriver in the alternator, it locks in one direction, and rotates in the other. The pulley wheel can move a little in and out. Is that normal? The pulley feels a little rough when spinning hard.
So likely clutch pulley is ok, I'd expect some end float in the shaft, I don't recall the cltch pulley it self able to do that, a littlre rough spinning hard, can't say but there's likely some noise and there are a set of old carbon brushes dragging on a worn commutator. if it's original . check everything else that spins, forgot there's a water pump in there as well. Gut tells me idler is most likely, keep digging

  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly

It feels like the shaft moving a little, and not the alternator pulley, so it is most likely fine then.

I have already changed 1 idler pulley, the top flat one, and the 2. pulley on the tensioner. The 3 pulley, one with the ribs feels fine and spins freely. 

The tensioner, when manually operated, feels strong and smooth.

The only other thing is the water pump, but i run smooth with no wobble.

As you mentioned, the problem maybe lies inside the alternator.






  • i30 1.6 crdi 2009 90 hp.

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  • au Australia
    Samford Valley
Try this, old trick, get a water hose, make as little water and narrow jet as possible, then briefly squirt each suspect part.
The noise may/should disappear with this temporary lubrication.

Its not timing chain!
  • Every FD model; BMW Z3 M; Mitzi Magna(mobile office)

Thanks.

I will try the water trick. Is it OK with water near the alternator?
  • i30 1.6 crdi 2009 90 hp.

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  • au Australia
    Samford Valley
Yep, just the same as driving on a wet day. Irrespective, if I get the alternator wet, I like to keep the motor spinning for a few minutes to dry it out.
  • Every FD model; BMW Z3 M; Mitzi Magna(mobile office)

Tried the water trick. Could not find the bad wheel. The water on the belt seemed to make the sound a little worse, as if the sound rises depending on the tension / belt load.

Can it be the belt tensioner, even though I have already changed the wheel on it.?

The noise has gotten a lot worse the last 48 hour. And is now present even when I am pushing the accelerator. The noise does not seem to follow the engine RPM but disappear over 1200 rpm.
  • i30 1.6 crdi 2009 90 hp.

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Sounds like alternator if you changed all the pulleys etc. I can bet it is a clutch pulley. They last around 150.000km.
  • 1.6crdi

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  • au Australia
    Samford Valley
The other test is a crude stethoscope: use a short length of rubber hose to your ear.
  • Every FD model; BMW Z3 M; Mitzi Magna(mobile office)

Changed the alternator today, and now the noise i gone!  :happydance:

On the old alternator, the pulley was a bit loud when I spun it, and the shaft could move in and out a bit. The new one was silent and had no in/out movement. Probably a worn clutch pulley, and maybe some worn bearings inside the alternator.

Thanks to everyone for helping me out.
  • i30 1.6 crdi 2009 90 hp.

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  • au Australia
    Samford Valley
Good result  :goodjob2:
Thanks for letting us know.  :)
  • Every FD model; BMW Z3 M; Mitzi Magna(mobile office)

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  • au Australia
    Devonport Tasmania
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Bwillient!  :happydance:
  • MY18 PD SR & 2014 1.6 GDi Tourer (Prev had 2008  i30 CRDi & MY11 Petrol CW)

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  • england England
    cheshire
Hi this sounds like a dry bearing on the alternator, as you say it gets worse when you switch things on, could be alternator working harder under load, or it could be something internal inside the alternator its self, maybe as the engine warms up, the noise is not as obvious
  • hyhundai i30 crdi

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  • au Australia
    Ipswich
Thanks for the feedback
  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly