Hard to see which orientation/pulley we are looking at, but the pulley seems to have a very slight wobble as the belt jumps, could it be a bearing? Could explain the “tick” sound?
New stuff can have a duff bearing.

Hi In video 1 You get a glimpse of the pulley as the belt jumps. The white shiny bit is the end cap to the pulley.

Looking at the video in landscape as it is. To the right is the electric fan.

This pulley is the one next to the alternator and has been replace twice. No change 2 new pulleys. The alternator is towards the bottom of the video. and the opt part of the belt that is running true is the section that goes to the water pump. As you can see after it leaves the alternator it is running true.

Sorry it is not the best video but with all the water pipes it is hard to get a good angle and keep some sort of focus.

Ok a quick update and maybe should have started here. With the belt removed. Not a peep. No clicking or squealing. I had noticed the active cornering oil level was slightly below min. So have topped this up. I also felt the pulley and there is slight forward back movement. Rotation is stiff. I have squirted some wd 40 between pump and pulley have put the belt back on. So far no squealing or clicks will only know for sure tomorrow when starting from cold. But maybe time for new pump.

OK another update.

After the squirt of WD-40 I have now had 2 days with no belt falling off, So i think I may be on to a winner. Well that is till you price up a new Active Stabilizer pump at £1300. So for my final testing I have ordered a good second hand one and going to use that for the final test before I spend the £1300

Can any one tell me if they have replaced one of these pumps before and if so other than contamination can I do this with out running the bleed process. I did read someone do this and just take the car for a 5 mile journey.

Thanks for any additional support.

On some cars and I don't know if the L405 is one of those there is a spacer washer behind the tensioner which if not refitted after a tensioner change will lead to the belt working its way off. An easy oversight that can have very serious and costly consequences.

Thanks baz000000
I think I have got to to bottom of the problem now, in that it is caused by a faults Active Stabiliser Pump.

I have had 2 + original tensioners to date. The problem started before I changed the tensioner and a lot of people have suggested it could be the tensioner at fault. Hence why it has been replaced so many times. The replacements have all made no difference and so I am fairy sure it was nothing to do with it in the first place.

I am currently looking for advise on changing the stabilizer pump and if it is something I can do without special tools/ diagnostics.

A new update will be available once I have changed the pump.

Well that was short lived. A replacement pump was installed and has made no difference. In fact made it slightly worse. Only at start up. Especially this morning when cold. I find it hard that I can not find anyone, who has had a similar issue. So this morning start the car. The belt falls off the idle pulley next to the alternator. Again loud clicking at the time. This does seem to temp related. But I am now at a complete loss.

I'd strip out the fan / fan cowling to make some decent working space and have a good look at every item the pulley goes around, pulling / pushing and turning each and every tensioner, looking for play / roughness.

As suggested - straight edge across all the pulley / tensioner faces, also make sure all items are compatible with your belt.

Also look at diagnostic live data to see if the clicking corresponds to the a/c clutch actuator. Perhaps it's engaging for a while at start-up even though a/c is off at the switch?

Also use diag data to see alternator output and whether this corresponds with the clicking?

Did it make it to the indi appointment you mentioned on 5th Sept?

Jon 1992 RR Classic 3.9 efi Vogue
2014 Disco 4 HSE
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Both my fatties now gone...
Previous: 2011 L322 4.4 TDV8 Vogue SE /// 2002 L322 4.4 V8 HSE /// 2009 Discovery 3 2.7 TDV6 XS /// 2004 Defender 90 TD5 /// 1993 110 V8 Snatch Landrover /// 2005 Discovery 3 2.7 TDV6 SE (Aus) /// 1990 110 Isuzu 3.9 County (Aus) /// 1976 Series III Trayback (Aus)

No I never took it there because I thought (Wrongly now) that it was the ace PUMP. When I asked if they would fit a second hand part they refused (rightly so) So I did the pump my self. Which has made it slightly worse if anything. Which kind of makes me think it could be to do with the fluid in the ace system. This has not been changed in my ownership 89k when bought to now 130k Miles so maybe this needs to be done. But would that cause it. I will check some outputs tomorrow.