Technical Odd Noise from Auxilary Belt on start up but not always

[FrankNicklin]

Got a 2.0JTD Motorhome on a 52Plate. Had since September last year and done about 1200 miles. Insisted that the cam belt and water pump were changed before purchase also had service and new MOT. I have a copy of the invoice from the garage. Also on the invoice is the replacement of the alternator/auxiliary belt. MH is in storage and never had any noises on startup or after our time away. Back in April when starting from a few days stop over there was a strange fluttering sound which disappeared after about 10 seconds. I lifted the bonnet and all looked good, belts in place and I didn't hear it again. About 30 miles in to our trip home and the battery light came on. Stopped at services and then also realised no power steering and my suspicions where right, the aux belt had gone. Anyway got it home and had the belt replaced. Tested at various revs up to 3000rpm for about 15 minutes no flutter and no bounce from the tensioner so all seems OK. We had another trip away with half decent weather, all good driving there and back, but after a 4 day trip away last weekend I started the engine and got the same sound which again disappeared after about 10 seconds or less. Checked under bonnet again all good, new belt running true. Drove home fine, no incidents but obviously this is now playing on my mind as to whether I could loose the belt again. This round trip was about 260 miles. The 2 times away when this has happened the front of the MH has been facing quite bad weather, driving wind and rain and I'm wondering whether water is getting on to the belt causing it to slip momentarily before friction takes over and it drys out and runs OK, but of course we have already lost one belt. All other stop overs we haven't had that bad a weather so just thinking this could be the cause. The lower cover plate is in place and there is a blank area alongside the radiator that sort of protects from the front to a point. There is no belt cover on the auxiliary belt. Have stopped and started engine since and not heard the noise. Any thoughts please.

 

[bugsymike]

Unlikely but bearings or stator coming apart in alternator.
Next time you start it and hear noise , have a quick look to see if alternator pulley turning as normal.
You may also place stethoscope/long screwdriver carefully on alternator to listen for any strange noises.
Also jockey wheel/tensioner on drive belt etc.