How to undo the auxiliary belt excentric roller bolt?

[frog]

I am trying to undo the bolt that is holding the excentric roller for the auxiliary belt. The tension roller (the other one) is vibrating terribly at idle revs, just like described in this topic. So i was thinking maybe the belt needs to be set more tight.

However, that bolt (holding the excentric roller) is stuck. Really solid stuck. It is a bolt with a 8 mm hex socket ("inbus"). I've got a tool set that has a small socket (1/4", like this one) that fits within the small available space, but the small rachet that goes onto it is just too short to put any force on it.

So I'm looking for a big socket: 1/2" (like this one) to fit on the big rachet, however that socket is 60 mm length which is way to big to fit within the small space.

Any ideas how i can put some force on the bolt holding the excentric roller?

[Doggy]

A good quality hexagon key, shortened to the minimum length to allow full engagement and a sturdy steel extension tube usually does the trick.

Another possibility - I have a set of hexagon keys that are about 30mm long, with a small hexagon one end, e.g. 4, 5, 6, or 8mm and a larger hexagon the other end - all 12mm I think. It's possible to turn one of these with a combination spanner in the space you have available.

[WillNZ]

Had this belt flapping on several of my hdi's, always been the clutch pulley on the alternator has siezed solid. Replaced it and flappy belt problem solved.

[frog]

@Doggy, that is a good idea. I have a set of these "driver" bits like this and like this. They are al 8 mm one one side and the largest is 14 mm on the other side. Then I can use a 14 mm spanner.

Or as you say a good 8 mm hexagon key with a long pipe over it; will try that. Thanks!

@Will - you mean the aircon compressor clutch? I am not aware that the alternator has a clutch, does it? I did remove the belt and check if all pulleys run free, and they were all running very light. With the belt on and engine running, the flapping seems at its worst when the aircon is on.

[WillNZ]

Nope, alternator clutch pulley, only my very early hdi didnt have one, all the rest have been fitted with them.

look like this... https://www.ebay.co.uk/itm/Alternator-F ... SwJtJcAUOE

[frog]

Ah, so it is a freewheel? Like the rear wheel of a bycicle, only engages in one direction and runs free in the other?

If it is stuck that would explain.... Will check. Thanks!

[frog]

Just checked, indeed seems to be the clutch pulled seized. I used a screwdriver to try and turn the vanes inside the alternator. It will not turn in either direction; i would have expected them to rotate freely in one direction.

Seems it is time for a new (or 2-nd hand) alternator.

Thanks for the suggestion!

[WillNZ]

Replacing the pulley is a mongrel job... getting the retaining bolt out requires a lot of heat to soften the oodles of locktite holding it in, and a special tool to secure it while trying too undo it.

I have more recently gone down the replace pulley route as have had a few secondhand alternators fail not long after replacement (pulley again). New alternators here are almost impossible to find and VERY pricey if you can, and auto electricians want arms and legs to fix broken ones, so I import pulleys from UK and fit myself. Pays to check brushes/commutator while you are at it if you go down this route.

[frog]

Replacing the pulley is a mongrel job...

I'm not replacing it, as you say special tools are needed. Picked up a second hand alternator yesterday afternoon for € 60; a parts dealer nearby claims to have 85 of them! I got one that came from a donor car which had ~ 100.000 kms on its meter.

I fitted it this afternoon (needs about 1,5 hours, very thin hands and ET-like fingers ) and indeed it is now much quieter! The specific "chirping" sound when pulling up has also gone. Keeping fingers crossed .

[WillNZ]

Sounds good! (pun intended..)

Not ever had a belt jump off with the clutch pulley seized though, just had to tolerate the insane clattering when idling and putting up with looks from motorists alongside..

[jasper5]

The easiest way to replace the alternator pulley is to grip the pulley in a vice and undo the nut with a socket and bar then knock the rotor part out complete with the alternator leaving the pulley in the vice.

[WillNZ]

That method does not work if you have a clutch pulley. The outer will rotate when you try to undo the centre bolt.

[jasper5]

It will work if the pulley is seized as in frog's case.

[frog]

Thanks for the tips . The old alternator seemed to be in good shape (apart from the pulley). No grinding bearings or such.

As Will says, "secondhand alternators fail not long after replacement", so I will keep the old alternator and in some spare time try to remove and replace the pulley by a new one. A short internet search showed a pulley for around € 20 so that would be better than swapping again later with another second hand alternator.

[Doggy]

A few years back I repaired the alternator on my daughters 807, using a kit of parts, (bearings, slip-ring assembly, brushes etc). that cost £9 from a guy in Ireland after watching his how-to video on youtube. (Could never have stripped it down without wrecking it prior to watching the video). Convenient thing was he was selling the bits as well.
Tried but can't easily find the same video today, but there are at least 5 others if you search alternator repair.
On the one I fixed, the slip rings had almost worn away to the point where the brushes were running on the plastic instead of copper for about half the surface. These, the brushes and bearings are about the only bits that won't go on forever, so if you can replace them and the pulley it should be good as new.