Not sure what this sound is but I’m really worried it’s going to blow up.

any body no what this sound is ?

audi A3 1.9 tdi 150,000 miles. 

Has oil in 

https://youtu.be/7WzdaKTd4Ic

You are right to be worried. Any knocking that loud should not be ignored. It's hard to be certain without hearing it from above and below the engine, and without using a stethoscope to locate the sound, but the most likely thing to my ear is a valve bouncing off a piston. I wondered at first if it might be a big end knocking but it doesn't sound quite metallic enough for that. Get it looked into immediately and it may only cost you a small fortune; delay the investigation and a new engine will cost you a large fortune. Sorry but it's going to be expensive either way.

Hello Richard,

As Cliff says - the bleeding obvious is that this car is trying to tell you something, and you must, just must, get this looked at a reputable local garage without any delay (delay in caps.) Failure to do this will demonstrate a lack of respect for the car and for your wallet. 

The fact that you are asking, suggests you don’t do much mechanicaly with this car yourself, but if it were mine, I would be disconnecting the auxiliary belt to find if the noise remains - and hoping it doesn’t, but if I were you, I would leave this for a garage to do. 

Perhaps you could let us know how you get on Richard.

Kind regards,

Gareth.