Replace alternator freewheel pulley on Mk5 Golf GT TDi

Just a quicky for you. I found loads of info on this for other models but not much in the Mk5 Golf forum. Reading other posts, this seems to be quite common and often overlooked in favour of replacing the auxiliary drive-belt tensioner which doesn't always cure the problem. Also not knowing about this and replacing your whole alternator could be very costly!

My alternator freewheel pulley disintegrated the other night and shed the belt but luckily no further damage. Took about 30 mins to replace, I spent longer researching the forums. I only needed to move the fuel filter (3 10mm bolts) for access. Reading around, other models were more tricky to get at. Getting new belt on was a little fiddly but could be a lot easier with the car raised and the splash trim removed but if you've got skinny arms then go for it!

You will need a special tool which I sourced from Camberley Auto Factors for £15.59+vat (see pic) This has the 33 splined socket for the pulley and a M10 12 splined bit which holds the rotating part of the alternator still and is apparently suitable for some Audi and VW vehicles but not my Golf! Mine needed a T50 splined bit which I luckily had in my toolkit. The splined socket was the important bit for me though and it's only a small spring clip to get it off and use other bits in it. There are kits available, a Sealey one springs to mind but was over twice the price.

Attachment 18926

What was left of my old pulley came off easily enough. It's a bit tight in the engine bay so I used a long breaker bar on the bit holder and a 17mm ring on the splined socket with another spanner interlocked for leverage. Don't get confused with the threads, you are unscrewing the pulley with the 33 splined socket anticlockwise and the centre bit is just stopping the rotating gear of the alternator from turning. Torqued the new one up to 85NM as recommended in its documentation, replaced the protective cap, put a new belt on and job's a good'un!

To help with putting the belt on, use a 17mm open ended spanner on the tensioner and pull down towards the front of the car just enough that you can pin it in place with a drill bit, allen key or similar. Whilst you're at it check the tensioner isn't loose or sloppy and the wheel rotates freely and smoothly. Obviously remember to remove the pin and gently let the tensioner back onto the belt once it is fitted!

The freewheel pulley was £26.50+vat and the belt (for vehicles with aircon) was £7.50+vat, both from GSF. Camberley were a few quid more but I got them to price match as they had the tool in stock.

Found a very useful post on this with loads more info here. Hopefully this will save somebody time or money. This Golf has just over 100k but my A3 has over 140k and the same type of pulley so maybe I'll get more use out this tool soon...