Hello, I would love some help with my cherished 2011 Octavia 4x4-120kmiles. It has a noise that only happens when it's been driven for over 20 mins. I have a video on you tube 

 

it doesn't appear to effect the power and doesn't struggle. Just sounds like a lawn mower. 

 

I have had two injector seals replaced on 3-4 as the injector surrounding looked a bit moist from a possible leak. But it hasn't fixed the noise. 

 

Any help would be great, I don't want to give up on it. Thanks. 

Total guess but maybe a dry tapet? I can remember old ford 1.3 would always have a tapety noise. 

Ye I think tappets or hydraulic lifters could be a route to look into. Thanks mdon for the reply.