Hello all, 99 L Series Hippo. So Friday while travelling back from Leicester my back box decides to disengage from the central exhaust. No biggie, replace the clamp Saturday morning and everything looking good again. However by Saturday afternoon the Hippo had developed a sort of whirring sound that increases with the revs (engine speed not road speed), no power loss, no smoke. Apart from the noise running fine. Checked all the hoses for splits just in case and they all look great. After a little more poking around I feel the noise could be coming from the left hand side of the engine so am starting to think it could be the aux belt?? Dunno if my imagination but it sounds a bit rattle and rough down there as well. Normally she sounds spot on and is quite quiet for an L. Any thoughts??

Probably the belt tensioner, take the belt off and give them a spin

Yes, be careful with the aux belt and its tensioner. The belt coming off, wrapping itself round the pulley and taking the cam belt out it probably the no.1 killer of L Series engines. The tensioner going/seizing is probably the No.1 reason the aux belt goes in the first place.

I got a bit paranoid at new year with a 'strange noise' that I was convinced was impending doom - even though nobody else could hear anything! The aux belt & tensioner checked out OK so I convinced myself it was the cambelt. Needed it done in a hurry, so spent good money with a garage to get the cambelt & tensioner changed and the noise was still there!

http://www.landyzone.co.uk/lz/f9/noise-timing-aux-belt-end-l-series-engine-273064.html

When this happened on my L series back box rubber went pulling apart from pipe put it all back with new rubber strange whirring sound from engine increasing as revs went up turned out to be leak/ blow in flexible pipe on exhaust.

Cheers all for the replies, gonna have a slide under and check the length of the exhaust as before my ham fists were interfering with the back box the sound wasn't there, failing that got it booked in on Thursday for the local garage to check out the belts. I'm very unwilling to fettle with belts. Unwilling/scared!

Checked the exhaust and that was fine so took it down to the local Landy service centre, called me today saying it was the tensioner and the belt was looking sorry too. Should all be fixed tomorrow!!