New engine noise when A/C on!

[STRANGETDI]

Hi all,

I hope you can help with this issue that arose this morning.
I now have a clicking noise when the air conditioner is on. This is what happened: I started the car to go to work this morning. I turned on the A/C (fan setting 1) after about 20 seconds of idling. I back out of the drive way with no problem, as soon as I shift to 1st and go forward (I get this clicking noise that increases with engine speed) Everything is working fine, but I now get this noise. At some point when I reach a speed high enough, I don’t hear it anymore (engine may be to loud at this point). When I decelerate, I don’t think I hear it at all or as much (as the engine is still loud when decelerating). Any ideas?

I turned off the A/C for my commute, but I only continued to test this at stop lights, and it happened everytime.

Is this a sign that something may be on it’s way out?

Thanks,

Chris

 

[scurvy]

It's hard to tell from your post, but I take it that you're now getting a clicking noise that keeps tempo with the engine speed. It would help to clarify the following points:

Does it happen every time you're moving forward?

Does it only happen when you're using the AC?

If you're driving along and can hear the clicking, what happens if you shift into neutral - does the clicking continue with the vehicle's speed or does it abruptly fall off as the engine goes to idle?

Does it get better / worse / stay the same as you swerve right or left and/or make sharp right / left turns?

CV joints going bad typically make a clicking noise in turns but it could also be many things. You need to diagnose it better before anything can be looked into further.

 

[Ski in NC]

Does noise occur only when ac is on? No noise with ac off?

If so, could be ac clutch or alternator pulley issue. AC clutch central nut is notorious for backing out, and can easily be tightened. Alternator pulleys are one-way clutches, also notorious for failure once the years and miles rack up. Alt shares same belt as ac. Tensioner can also wear out.

 

[STRANGETDI]

Does it happen every time you're moving forward? YES

Does it only happen when you're using the AC? YES

If you're driving along and can hear the clicking, what happens if you shift into neutral - does the clicking continue with the vehicle's speed or does it abruptly fall off as the engine goes to idle? FALLS OFF AS ENGINE GOES TO IDLE

Does it get better / worse / stay the same as you swerve right or left and/or make sharp right / left turns? I'LL HAVE TO TRY THIS AND SEE

CV joints going bad typically make a clicking noise in turns but it could also be many things. You need to diagnose it better before anything can be looked into further. NOT CV JOINT, ALMOST POSITIVE

Thanks

 

[STRANGETDI]

Does noise occur only when ac is on? No noise with ac off? This is correct.

If so, could be ac clutch or alternator pulley issue. AC clutch central nut is notorious for backing out, and can easily be tightened. Alternator pulleys are one-way clutches, also notorious for failure once the years and miles rack up. Alt shares same belt as ac. Tensioner can also wear out. Interesting, very possible, but don't know at this point.

Thanks.

 

[STRANGETDI]

Does noise occur only when ac is on? No noise with ac off?

If so, could be ac clutch or alternator pulley issue. AC clutch central nut is notorious for backing out, and can easily be tightened. Alternator pulleys are one-way clutches, also notorious for failure once the years and miles rack up. Alt shares same belt as ac. Tensioner can also wear out.

Where is this AC clutch central nut located?

I do have 191,000 miles on it.

 

[Ski in NC]

Nut is right in the center of the ac clutch. 14mm I think. A little tight there to get a wrench in. Some car stuff is in the way. Easiest to get to from the bottom with some of the plastic junk moved out of the way. Need to hold clutch while tightening nut.

Mine was loose at 115kmiles. Put the hoodoo on it and it has stayed tight.

 

[scurvy]

Does it happen every time you're moving forward? YES

Does it only happen when you're using the AC? YES

If you're driving along and can hear the clicking, what happens if you shift into neutral - does the clicking continue with the vehicle's speed or does it abruptly fall off as the engine goes to idle? FALLS OFF AS ENGINE GOES TO IDLE

So it's definitely something before the transmission even though the first and second statements are incongruous - you don't ALWAYS have the AC on, do you?

I would check the AC compressor clutch nut as Ski in NC mentioned, it is 14mm. Also check the area around the compressor/serp belt to make sure there's not a twig or leaf in the area.

Has the AC changed effectiveness recently?

 

[STRANGETDI]

So it's definitely something before the transmission even though the first and second statements are incongruous - you don't ALWAYS have the AC on, do you? It only happens when the AC is on when moving forward. This only started to happen this morning.

I would check the AC compressor clutch nut as Ski in NC mentioned, it is 14mm. Also check the area around the compressor/serp belt to make sure there's not a twig or leaf in the area.

Has the AC changed effectiveness recently? Nope, seems to work fine.

Thanks. I'll check my Bentley Manual for this nut location. I do my own repairs when I can, so if this is easy. I think I can do this.

What do you mean, hold the clutch when tightening the nut? It may seem self explanatory when I get in there.

 

[SheeB]

When you go to tighten the 14mm nut, the clutch assembly will just spin.

 

[PolitesTDi]

If I need an A/C clutch only (compressor is fine) where do I find one? Do I have to piece it together myself or can I buy a kit?

 

[Dunno513]

Have you taken a look at the area around the AC Compressor... Almost sounds like something is up against the compressor and the compressor engagement disk is hitting something when it is spinning. If not it sounds like it's something internal to the compressor.

 

[PolitesTDi]

When I engage the A/C the noise stops, my buddy says it's because the magnet engages and pulls the clutch up far enough that it stops rattling (or something like that). No A/C cooling, so I'm guessing it's internal anyway.

 

[STRANGETDI]

Thanks for the suggestions guys. It turns out the issue was a bad tensioner, causing the belt to vibrate and shake to be audible when the A/C was on. New belt and tensioner goes in on Monday. Hopefully it doesn't go in the next few days. Knock on wood......

 

[Dunno513]

Might be safer to just take it off till then...

I have read where at least one serp belt became shrapnel for the TB. I'm not a gambling man when it comes to cars, especially this one.

 

[STRANGETDI]

Thanks for the suggestions guys. It turns out the issue was a bad tensioner, causing the belt to vibrate and shake to be audible when the A/C was on. New belt and tensioner goes in on Monday. Hopefully it doesn't go in the next few days. Knock on wood......

The tensioner and belt were replaced, but the noise still exists. I do beleive my trusted mechanic, that the tensioner was bad. He now thinks it is the A/C compressor.

I will try tightening the AC clutch central nut first and see if that fixes the probelm. I certainly do not want to spend $500 + labor on an A/C compressor at this time.

 

[STRANGETDI]

New Update:

Everything related to the serpentine belt, tensioner, and associated pulleys seem to be ok as all were replaced this weekend. The car is fine from a driving standpoint, just don't use the AC. It isn’t the AC components at all that are the cause of the noise. But this noise happens when the AC is on, which puts load on the engine. The noise is coming from the top of the engine. Through touch, feel and hearing, it's seems to be coming from the injection pump area. Has any one had this issue? Or an idea? We also pulled the timing belt cover off and there are no issues in there either.

 

[STRANGETDI]

Sound is similar to this: (the first one about 19 seconds)

http://www.youtube.com/results?search_query=TDI+injector+pump+noise&aq=f

 

[STRANGETDI]

Update:

I'll take the car back and drive without the AC. They can't figure it out. May take it to a local TDIclub guru.

From a PM by Meganuke earlier today:

I can't see the youtube video due to work filters, but here's a guess. When you turn the A/C on, the ECU bumps the injection quantity to compensate for the parasitic loss from driving the A/C compressor. If you have VCDS, watch the IQ at idle with the A/C off. See if it is stable. It will typically bounce between two numbers that are .2 away from each other (3.2 and 3.4, for example). Turn the A/C on and see what happens to the IQ. The quantity adjuster in your injection pump could be marginal given the miles on it, and using the A/C pushes it over the edge and it may be having a hard time keeping the IQ stable. If the IQ amount is fluctuating more than .2, then the pump should be rebuilt, but you can still drive the car for a while. It'll get harder and harder to start until it gives up completely.

Hope this helps.
Keith

I do have Vag-Com and will check this. I have also seen threads about bad seals and air leaking into the system......