05 2.0 dti

While in for 65,000 service at VX, I asked them to investigate a noise I keep hearing, it sounds a bit like belt slipping at about 2000rpm, it can also be heard when changing gear 1st to 2nd especially, it makes no difference whether the engine is cold, whether it's wet or under any load the noise is still there. I have examined the belt and all seems fine, the noise does appear to come from the top of the engine. VX say the turbo is knackered but I can't say I've noticed any difference in performance.

In your opinion are VX correct or does it need further investigation, I've never had any need to really doubt my dealers judgment before (unlike some others).