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AHU TDI Vibration Damper Pulley testing
Posted: 31 Mar 2025, 15:29
by hotpod
Does anyone know how to test if the vibration damper pulley ( harmonic balancer) on the crank shaft is in good shape?
Mine drives the ribbed serpentine belt for the alternator and water pump and has a pulley for a v belt to drive the power steering pump on the outside.
It looks fine on the engine (no play or anything) but I didn't even know I had one or what one was until a mate pointed it out whilst we were trying to diagnose the noisy engine in the camper. Turns out that the water pump pulley wheel is hanging and the bearings in the pump have a lot of play plus the tensioner pully bearings are also knackered so it might just be those but I dont want to put it all back together without knowing if the damper pulley is shot too.
Any advice much appreciated.
Re: AHU TDI Vibration Damper Pulley testing
Posted: 31 Mar 2025, 19:21
by silverbullet
Are they known for failing? Unless the rubber bonding between the hub and pulley is obviously degraded, split or has chunks missing then I wouldn't worry.
Probably just a failed water pump bearing and the tensioner can't cope or has also failed.
Re: AHU TDI Vibration Damper Pulley testing
Posted: 01 Apr 2025, 07:27
by hotpod
I have no idea if they fail but new ones are for sale so I would guess they do.
Nothing obviously degraded but I was wondering if there was a rule of thumb type way to tell.
I will take it off and do an inspection since this is likely the best time to do it
Re: AHU TDI Vibration Damper Pulley testing
Posted: 01 Apr 2025, 13:48
by silverbullet
I have seen delaminated crank dampers on other engines but its a rare thing. If it has a TDC mark then check if it lines up, if not then its loose.
Re: AHU TDI Vibration Damper Pulley testing
Posted: 04 Apr 2025, 18:01
by Burtybassett
My last engine was an AHU....I had my pulley replaced when I did the cambelt (which should be done every 4 years regardless of milage) as mine was squeeking and rattling due to shot bearings.
Parts are/were quite common.
This was.....2020.
Re: AHU TDI Vibration Damper Pulley testing
Posted: 04 Apr 2025, 18:42
by Oren Kipnis
Which Alternator is mounted on the engine ?
Does it have a clutch pulley ? It is essential on these.
Re: AHU TDI Vibration Damper Pulley testing
Posted: 05 Apr 2025, 10:51
by hotpod
Burtybassett wrote: ↑04 Apr 2025, 18:01
My last engine was an AHU....I had my pulley replaced when I did the cambelt (which should be done every 4 years regardless of milage) as mine was squeeking and rattling due to shot bearings.
Parts are/were quite common.
This was.....2020.
Which bearings were shot? and are you talking about the pulley which bolts to the end of the crank shaft and drives the auxiliary belt?
Re: AHU TDI Vibration Damper Pulley testing
Posted: 05 Apr 2025, 10:52
by hotpod
Oren Kipnis wrote: ↑04 Apr 2025, 18:42
Which Alternator is mounted on the engine ?
Does it have a clutch pulley ? It is essential on these.
Ii have the 90a and it doesn't have the clutch pulley. I shall look into getting one asap.
Re: AHU TDI Vibration Damper Pulley testing
Posted: 28 Jun 2025, 08:52
by hotpod
I bought a clutch pulley and tried to fit it yesterday. It didn't go very well. the axle of my Valeo alternator with the fixed pully is 20mm and the and only catches the clutch pulley by a couple of threads. Plus, the Valeo has a recess around the axle into which fits a sticky-outy bit on the normal pully . The clutch pulley is flush on the back so it tightens itself al the way to the body of the alternator and jams. Obviously not good
So I'm looking for an alternator with a clutch pulley already fitted.
I have a suitable old Bosch one here but its minging inside and out. I may look into getting it refurbed but I suspect just getting a new one will be more cost effective. The Bosch one has the sticky-outy bit ( a technical term) on the alternator body around the shaft and the shaft is 10mm longer.