Audible hissing noises from 1.9TDI Golf

[Celestine]

I actually dont own a Golf 1.9 TDI myself, but a friend is having issues with his one. My friend initially described the sound to me as an ambulance siren type sound. This puzzled me so he brought his car over for me to have a listen.

Upon hitting boost at just over 2500 rpm, there is sometimes an audible hissing noises. I myself arent very clued in on turbo's or diesels for that matter of fact, but I'm guessing there is a chance of boost leak.

Anyone have any ideas on what other possibilities it might be? It's being booked in to get checked out, but any explanation would be nice.

[gregozedobe]

Leaking intake air (after the turbo has pressurised it) is the most likely cause of the hissing noise, there are lots of large and small diameter hoses and pipes and connections that could be leaking.

The 1.9 should be making good boost by about 1,900-2,000 rpm, so I would have thought you would hear a boost leak well before 2,500rpm.

Probably best to have someone with TDI experience and knowledge to check it out (VW specialist or dealer).

[gldgti]

or just inspect all oyur intake hoses yourself. start at the airbox, follow to the turbo, then out of the turbo, etc. do a visual check first, then look for any monor oil sprays (where oil may be leaking from the intake hose because it condenses out of the intake air.)

[Greg Roles]

I can add that my car makes what I would call a squeaky flutter sound when boosting hard, and I was concerned I had a loose connection too. Jamyz TDI made exactly the same noise when he let me drive it, so it may be a normal noise you are just noticing with the windows down??

[gldgti]

I can add that my car makes what I would call a squeaky flutter sound when boosting hard, and I was concerned I had a loose connection too. Jamyz TDI made exactly the same noise when he let me drive it, so it may be a normal noise you are just noticing with the windows down??

BOV doing its job.

[Mischa]

my mk5 does it too. so do all diesel trucks you hear trundling past you. its nothing to be worried about i dont think. it sounds like a "siren" as you put it (or whistling as id put it lol) when the windows are down and less noise gets through.