GL320 engine hissing noise
 

Hi, I am new to forum so please bear with me. Couple of questions for the experts.
1. there is a distinctive hissing noise at 1500-2000 rpm. Only while accelerating. Doesn't come on while the truck is in park even when you press gas to get to 1500 rpm.
2. Adblue heater needs replacement. Reading through the forums it seems like a common occurrence. Is there any class action / recall

The truck has SCW till mar 2015. So far no matter what's it gone in for , it isn't covered for one reason or another.

1500-2000 is where the most aggressive turbo boost is..... you aint getting it in park because boost shows only under load.

the air intake should be checked for misalignment, lose hoses... especially where it mates to the turbo intake - there are two orange seals there - one large for the turbo seal and one smaller one (on the left of the large seal) for the recirc hose.

Thanks for the response Alx. I took it to the dealership and the foreman took it for a test drive. Seems like the turbo. It's booked for service next week. Hope it's covered under SCW. Thx