T6 Squealing Auxiliary Belt - Might Not Be The Tensioner

Blanco · Apr 22, 2026

Starting the van from cold to move it on the driveway before packing for a week away and the engine let out a massive shriek. After a few seconds the noise quietened down and everything seemed to run as normal. However, every time the engine started there was a momentary loud squeak. Sounded like the sudden escape of pressure from something.

Suspicion fell on the auxiliary belt tensioner having failed although investigation indicated nothing wrong. BUT the centre section of the crankshaft pulley that drives the auxiliary belt could oddly be rotated within the pulley itself by about 1.5cm in either direction, which I’m told really isn’t meant to happen.

On T6’s the centre of the pulley carrying the auxiliary belt is apparently bonded to the outer part with a rubber anti-vibration cushion (I’m sure there’s a proper way of describing this) and it seems the two can decide to part company all of a sudden. When it occurs and the engine starts the outer pulley attached to the crankshaft rotates until it takes up the slack in the cushion at which point the auxiliary belt engages with sufficient jolt to stretch it before the tensioner spring reacts and almost throws the belt off the tensioner wheel causing the squealing. The sound of pressure escaping presumably is trapped air in the void worn inside cushion being forced out.

This was less than 40 miles after the auxiliary belt had been replaced at 56k miles. The original VW belt taken off was 1555mm long, and the replacement 1548mm. VW had once I’m told realised the longer belt was too long for the tensioner and shortened it 7mm. I’m thinking the shorter belt put extra pressure on an already partly worn cushion causing it to fail.

Does this sound broadly familiar to anyone?

New pulley then. Rather more expensive unfortunately than a tensioner … £570 plus bolts. Ouch. At least it happened at home and not the middle of Wales halfway through our trip. Every cloud as they say has a silver lining. Me just trying to remain positive!

sidepod · Apr 23, 2026

Crankshaft damper is the correct name. A mass damper. Damps vibration.

Blanco · Apr 25, 2026

Turns out this was a tale of misinformation. If anyone tries convincing you an Auxiliary belt 1548mm long is the correct length then in your own words tell them to do one. Auxiliary belts for a California ie Transporter with AC have to be 1555mm. The VW spares shop had no knowledge of the belt ever having been shortened 7mm …
Threw the BG belt out and fitted a genuine one 6PK1555. Afterwards not the slightest hint of a shriek and other frightening noises that had been coming from the engine.
Oh and if anyone says the centre of the pulley shouldn’t rotate at all, well that’ll be tripe as well.
140 miles to north wales and so far running perfectly. Stonking weather too.

sidepod · Apr 25, 2026

Nice mutt

Blanco · Apr 26, 2026

Mrs B’s irish angel.

Goldie · Jul 17, 2026

My 2017 2.0 Beach (14K miles) failed its NZ Warrant of Fitness (WOF) - (same as MoT) - a couple of days ago on the left rear ABS sensor and 'Steering mechanism'. It was the auxiliary belt which they rated as 'damaged' or 'significantly deteriorated' according to the failure criteria:

The power steering system, either hydraulic or electric:
a) has been disconnected, or
b) does not operate correctly, requiring unreasonable force to steer the vehicle, is unreasonably light, or
c) has a hose, pump drive, drive belt or pump mounting that is insecure, damaged or has significantly deteriorated, or
d) has a significant fluid leak
e) has a warning lamp or self-check system that indicates a defect in the power steering system.

They must have failed it based on the slight whine from the engine when ticking over. As the belt has no cracks or visual damage and is the same length and thickness 4.6mm as the original. The only difference I can see is that the V groves may be slightly worn on the original - hardly seems a reason for the WOF steering failure.
When researching replacing the belt I noticed that there are two different routes. The diagram on Autodoc for the Contitech belt has the idler between the Power Steering and the Alternator, whereas my engine has the idler between the Aircon and Power Steering. I've included a picture and a diagram. It would be easy to take the old belt off and then put the new one on following the wrong route - it may not make a difference, but they must have changed it for some reason. Mine is the same as this.

- I will admit the whine has now disappeared now I have replaced the belt.

Waiting for a set of ABS sensors to arrive from UK to fix the ABS issue and will then get it retested - I can buy a set of 4 for the price of a single one in NZ.

I think I will avoid taking it to my local VW garage for a WOF in future as they may be looking to 'upsell' on the back of the WOF (MOT), e.g. they quoted over £300 for the sensor and belt replacement. The ABS sensor is a valid failure, but the belt seems an opportunity for them to make a bit more profit.