That's what I was thinking so I was wondering if there could be something blocked up It's only just done it again and it goes away once it's warmed up You can hear it much worse inside the car than you can with the bonnet open

Is it worth running some engine flush through it then changing the oil & filter? The car has done 87k and the oil was last changed last April/May time with Mobil 1 15w/50w I think.

Thanks