'06 jetta idle knocking

llcooljc

Well-known member
Joined
Mar 20, 2013
Location
WI
TDI
06 jetta
When coming to a stop after the car is warmed up, the car is idling just fine. Mixed in randomly with the whirl of the engine is a knocking type sound. (not sure how else to describe it). It is totally random and only occurs when warm. If I press the pedal to increase rpms, it disappears. Anyone?

Also, it is a manual trans. 210k miles. pressing or releasing the clutch and/or brake seem to have no effect.

Thanks
John
 

llcooljc

Well-known member
Joined
Mar 20, 2013
Location
WI
TDI
06 jetta
How does one know/tell if a dmf is failing? (without ripping everything apart)
 

craig01b

Top Post Dawg
Joined
Mar 17, 2004
Location
Guelph, Ontario.
TDI
None
Usually vibration for the dmf, have your had your cam done yet? It may also be wear on the cam, that also is a fairly simple inspection if you pull your valve cover off.
 

llcooljc

Well-known member
Joined
Mar 20, 2013
Location
WI
TDI
06 jetta
I replaced the cam etc with one from Frank about 2k miles ago. (yes, the knocking i am talking about now was present before the cam change as well).
 

nord

Veteran Member
Joined
Mar 5, 2010
Location
Southern Tier NY
TDI
All turned back to VW. Now a 2017 Hundai Tuscon. Not a single squalk in 10k miles.
I'd tend to suspect an alternator clutch assuming all else mentioned above has been checked. The DMF is usually diagnosed by the sound of "marbles tossed into a coffee can" and shaken. Thus, I tend to doubt DMF.

Engine mount? Maybe but unlikely. Possibly the a/c compressor but these don't really cycle on and off like other cars.

And so back to the alternator. Have a look at your belt tensioner and see if it jumps around. I'd tend to expect that it's not running smoothly and that every time you see a good jump you'll hear the noise. Pop the plastic cap off the alternator pulley and you'll encounter a rust-like coating. If so, look no further as you'll have located the culprit.

Merry Christmas and good luck.
 

MyAvocation

Top Post Dawg
Joined
Jun 9, 2004
Location
Hoffman Estates, IL
TDI
2017 Passat SEL TSI
Are you sure knocking is coming from the engine bay?
A5s are know for an annoying, intermittent knocking noise in the cabin, near the glove box. This particular noise knocks about 5 times, then stops. I still don't know the source, but it sounds like a vacuum-assisted vent flap having an epileptic seizure -- most noticeable when motor up to temp and at idle.

Definitely check your Alt pulley, as it will lead to bigger problems.
 

llcooljc

Well-known member
Joined
Mar 20, 2013
Location
WI
TDI
06 jetta
I doubt it is the alternator pulley, as I replaced that about 6 months ago...and the belt tensioner is steady as a rock.

I would say it sure sounds like it is coming from the engine bay, and not near the glove box.

Thanks for the replies.
John
 

llcooljc

Well-known member
Joined
Mar 20, 2013
Location
WI
TDI
06 jetta
How does one tell if the dmf is going? (without digging into everything)

Thanks
John
 

Jergren

Active member
Joined
May 20, 2010
Location
Indianapolis, IN
TDI
2006 Jetta TDI manual
I doubt it is the alternator pulley, as I replaced that about 6 months ago...and the belt tensioner is steady as a rock.

I would say it sure sounds like it is coming from the engine bay, and not near the glove box.

Thanks for the replies.
John
Don't guess the pulley is good without confirming that it is. It would be a ***** if you replaced the flywheel/clutch and the noise didn't go away.
 

strommer

Veteran Member
Joined
Jan 4, 2005
Location
Brampton, Ontario, Canada
TDI
Jetta 2006 platinum
My 06 had a knocking sound and it was the accessory belt tensioner pulley that was shot. To check this, put a wrench on the square of the pulley when engine is running and put some tension on it by pulling to hear if sound goes away. Mine did so I bought a new one. Easy fix for something I thought was more major. Good luck.
 
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