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Audi A6 The mid-sized Audi A6 model offers more room to the driver and passengers over the A4 line.
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  #1  
Old 12-31-2009, 01:07 AM
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Default Timing belt Serp belt noise? cross post, but please take a look

http://forums.audiworld.com/showthre...7#post23905087
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Old 12-31-2009, 02:24 PM
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Jeff, I would say the same as the guy on AW:
try to run it without the ribbed belt and see if the noise goes away. I would have guessed that the ribbed belt tensioner is bad, but you said you had it changed as well.
(Was it brand new or used?)
I know that my old tensioner was producing a similar noise. The AC compressor pulley can also make a noise.
One other thing I would check before taking it back or to a diff shop is the tension on the TB. Maybe it loosened up - that's why the noise starts when revving it up./
Keep us posted pls.
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Old 01-01-2010, 01:07 PM
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Well it's be isolated to the serp belt area so that's good. Now we just have to determine what it is. It was making the nice loud noise yesterday when I brought it back to the shop. Of course when the tech and I walk out, it was silent. Grrrr. The tensioner was new, all the parts were new. My fan clutch was also new in the last 5k. For the serp belt, we only changed the belt and tensioner. They said all the other parts felt solid, so they didn't change anything else. Doesn't mean one of them didn't decide to die now.

The good news is I don't have to worry about my timing belt snapping. I can live with a serp belt failure until we figure this out.
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Last edited by Jeffla; 01-01-2010 at 01:09 PM.
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Old 01-01-2010, 04:10 PM
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Well, if it was isolated to the serp belt, then one of the following is producing the noise:

- tensioner (it can be double checked by hand rotating it - the pulley on my old one had a "raspy"/grinding/rubbing sound and feel to it as comparative to the new one),
- AC compressor (you can squirt a little bit of oil right behind the pulley so would trickle onto the shaft), or
- the alternator pulley/bearing
- PS Pump pulley/bearing
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Old 01-02-2010, 11:09 PM
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Turn the AC off and see if the noise goes away.
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  #6  
Old 01-03-2010, 12:16 AM
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Turning AC off not always helps:
1. check tensioner by removing the belt (do not run more than 10-30 secs)
2. check AC pulley by (if you could get - shorter belt for models without a/c).

Sounds really like a tensioner (made in china?)
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Old 01-03-2010, 01:06 AM
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A/C is turned off.

It makes more noise as you increase load on the engine. Meaning, if I turn on everything possible, high-beams, rear window defroster, blower motor on HI... the noise gets louder, turn off everything and the noise gets a lot softer.

I have no idea where the tensioner was made. My shop insists on name brand parts. But to be honest, I don't know what brand went in there.

What puzzles me is why the noise takes 5-10 minutes of driving to start. You can let it idle all day and the noise never appears. Drive it for 20 and it's noisy, then let it idle for 10 and it's quite again. My biggest problem is our garage is not heated, we have a heater, but in -11deg weather her in MN, it's too damn cold to mess with it.

For now I'm just going to drive it until it gets worse and the mechanic can finally diagnose it, it gets warmer, or breaks of course. Normally I'm willing to troubleshoot, but it's just too cold to mess around in a unheated garage.
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Old 01-03-2010, 05:43 AM
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It sounds like the alternator works harder to offset all the power needed by all those accessories turned on.


Here's something interesting:
Quote:
So, how can you tell if the alternator is failing without taking it apart and doing some measuring inside the alternator? It's really pretty simple. You will need a simple voltmeter. You can get one at Radio Shack for under ten dollars. Here's what you do - start the car, make sure all the accessories are off and rev up the motor to a fast idle. Set the Voltmeter to the DC scale (not AC or Ohms). Measure the voltage across the battery terminals - red lead of the voltmeter on the positive terminal, black on the negative (ground in most cars). The voltage should, and probably will, read around 14 volts. If it reads less than 12 volts you may indeed have a failed alternator and you can skip the next step. Next, turn on the heater, the rear window de-fogger, the radio, the headlights and anything else that draws power. Now rev up the motor and watch the voltmeter. It should still be reading around 14 volts. If it reads lower than 13 volts the chances are that your alternator is not up to snuff.

One last failure mode is of course noise. The rotor inside the alternator rotates on bearings, normally very high precision needle bearings, and these can fail. When they do you will hear a loud grinding noise associated with the alternator. To isolate the noise take a length of tubing, heater hose will do fine, put one end to your ear and move the other around in the vicinity of the alternator. The noise will be much louder when you point it at the alternator if that is the culprit. Other possibilities are the water pump and the power steering pump which are also driven by the engine belt. To further isolate the noise disconnect the drive belt and spin the alternator by hand. If you hear a rumble or grinding noise then the bearings are shot. If you don't hear a noise the problem may still be in the alternator since the bearing might be quiet without the loading of the drive belt tension. Check for side play in the pulley. If you are pretty certain the noise came from the alternator it is a relatively simple task to take it apart and visually inspect the bearings, else swap it in for a rebuilt. Your auto supply store will normally bench test the alternator free of charge and can tell you at that time if the bearings are noisy.

Before you go running down to the parts store for a new alternator make sure to check the connections at the battery terminals and also check to see that the voltage is the same at the alternator terminal (the big fat one with the heavy wire attached) {also, read the article, dead battery}. Check to make sure the belts are tight and not slipping. Replace them if they are cracked or shiny on the side that faces the alternator pulley.

One final thing to check - the field voltage. In order for the alternator to generate electricity it must be supplied with a field voltage. If you know which wire is the one that supplies the field (normally labeled 'F') then simply check with a voltmeter to see if there is 12 volts at the field. Another check is to use a hacksaw blade or a lightweight screwdriver , anything magnetic, and hold it near the side of the alternator with the ignition switch turned in the on position. If there is a field voltage present then the metal will be attracted magnetically to the side of the alternator, not very strongly, but you will feel it pull the metal to the side of the alternator.
As far as the darn cold and garage, I'm two degrees below you. Jim is right in between us, with an "aerated" shed . I have no garage...
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Old 01-03-2010, 05:43 AM
 
 
 
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2009, a5, a8l, alternator, audi, b7, belt, elantra, failed, hear, idlertensioner, making, noise, pulley, timing


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