Cold start noise ALH

[endreo]

Hello everyone.

I have a problem with my mk1 Octavia 1.9 TDI (ALH engine). There is a noise coming from the passenger side after cold start. I was suspecting the dual mass, but if I press the clutch in the sound doesn't change at all. It goes away if I blip the throttle and comes back as it continues to idle. The sound completely goes away if the car is warm, and it doesn't do it on every cold start. It is a strange noise because if I open the hood I can not hear it, only if I lean next to the wheel from the outside. I have changed the serpentine belt tensioner before (which still rattles a bit on cold) but if I press on it the sound doesn't change. I did some research and only thing I can think of is the oil pump chain.

Anyway I did a video of the sound I hope you can help me with some ideas what this could be.

(21) ALH 1.9 TDI cold start noise - YouTube

 

[cjolson140]

My 99.5 Jetta (ALH) makes exactly the same noise! The unusual part is that after idling for a few minutes, it will suddenly (instantly and completely) stop rattling and become silent. I had the timing belt, water pump, and alternator changed maybe 20k miles ago, and I’m starting to suspect either the serpentine tensioner or the alternator clutch pulley but I haven’t really looked into the issue.

 

[endreo]

Yeah it does stop by its own sometimes after a few minutes. But I did notice if I drive it and stop again and the engine is still cold I can still here it on idle. I was thinking about the alternator clutch pulley as well,, but I'm not sure. It just concerns me if its the beginning of some bigger problem.

 

[Vince Waldon]

How old is the timing belt system (rollers, idler, etc) ??

Rattling at that side of the engine can be bearings on a timing belt roller or idler that are starting to rattle a bit... tends to go away as they warm up.

Just did the belt on my daughter's ALH that had some first-in-the-morning rattling... once I got 'em off and spun 'em the bearings on both rollers and the idler were definitely starting to make a bit of noise, especially with the new parts in your hands as a comparison. Timing belt wasn't due for another 75K but we decided to do it early, in part due to the increased rattling that we couldn't track down otherwise.

All noise now gone... other than the usual beloved diesel chatter, of course.

 

[endreo]

It is due soon. Around in 25k miles. I will try to replace the alternator pulley first and if doesn't change, soon the timing belt needs to be replaced anyway. So two big possibilities will be addressed. It has been doing it for almost a year and the sound didn't get worse.

 

[Genesis]

Oh, that sounds like the alternator pulley starting to get wonky.... might be wrong but....

 

[endreo]

Thanks for the replies. I will let you know if changing the alternator pulley fixed the issue.

 

[endreo]

The whole timing belt kit was changed. The noise is still there time to time. I have checked the alternator pulley by turning the fins inside the alternator and it spins freely one way and blocks the opposite way just how it should be.

The belt tensioner was also replaced. There still quite a bit of audibale vibration from the tensioner when cold, and if I touch the top of the small shock of the tensioner, the small rattle stops, but it doesn’t have an effect on the noise in question. Still somehow I feel like the two things are connected.

It is so strange because if I just blip the throttle a bit, it goes away. If I press the clutch it doesn’t effect the noise. At first it totally sounds like a DMF rattle. Also it’s not really audible from the top of the engine if the hood is open. Only from the passenger side wheel arch. Sometimes the noise disappear suddenly after a few minutes of idling. What else could be the problem here?

 

[Sauaciden]

I have some type of noise aswell coming from timing belt side when engine is cold. It goes away few minutes after cold start when turbo charger vanes start working. My TB has been replaced recently with all rollers. Turbocharger is in excellent condition. Car came from factory with SMF. That had been replaced aswell when my clutch went. I wonder if its turbocharger making that noise. Bliping throttle should force turbocharger to make minimal boost