Got a wee problem with my 1.8T, been running fine since i have had it, but its now developed a whine when under mid to heavy boost conditions, it sounds like an electric drill spinning up, the car boosts ok ish, it isnt as quick as it was, but it still boosts, no smoke, no rattles, its just this annoying whine.  Now i am pretty sure that it is a boost leak, and i am sure it is coming from the intercooler or pipes that run to it as that is where the sound is more prominant.  The only mods i have is the 249 bypass, drilled airbox and ebay recirc valve, it has been running these for about a week now and not had this problem till today.  I have checked the pipes at the top of engine and from the intercooler to inlet and these are all fine, could it be the connecting pipe from the pancake pipe to intercooler, or from the turbo to pancake pipe, or even the intercooler itself? it was laid up for a few months before i got it, any others had this problem?

Does it sound like that?

If so, mine has been like that since my downpipe was replaced over 12months ago and performance hasnt changed. As the downpipe started to break the drill sound got louder

Yeah sounds abit like it, just a bit louder, but that was because i had the windows open.  What makes me think its a boost leak is that the "drill" sound fluctuates as boost reaches peak, like the ecu is trying to pull back or compensate in some way.

Sounds just like this.

Update to this problem, still haven't found the boost leak.  I have replaced the metal charge pipe on my AUM with the better jubilee clip design one from the AGU in the hope this would fix it, but alas the screech remains

 

https://www.youtube.com/watch?v=QcxGz2Zz5Oo

 

This is the exact noise and problem i have.  I found this on the mkiv forums.

 

Any Ideas anyone?

 

 

Mine sounded like that when my flexi on the downpipe was going

I think you might be best getting a smoke test done for this. It sounds like a very slight split/leak in a boost pipe somewhere and trying to find that could be tricky. It is possible to make a device out of baked bean tin and a tyre valve!! I was going to make one a while back just never got round to it.

I love that sound....really

I think i may have found it, i just checked around the connection to the pancake pipe from the rubber hose that connects to the boost pipe, and i found a small amount of oil at the jubilee clip, so i think it may be leaking there.  Time to get a new pipe.  Anyone know a good place to get one? i tried skoda a couple of weeks ago and they wanted £65 for it (i was just gonna replace this pipe in the first place, but the older style boost pipe came up at a good price, so i cut the clip off the old rubber pipe and reused that one, and it not that point its leaking, thats fine and nice and clean)

 

I have looked all over for one and cant find that one, i can find the top hose all day long, not that bottom one.

Most 1.8t have some oil leaking from that pipe so its unlikely to be your problem

Never say never that is defo a air leak mate or your turbo on its way out does it still pull ok ?

When the turbo bearings fail it sounds like the siren on a police car all the time you are accelerating, even when gently. Yours sounds more of a leak plus a little of turbo bearings noise in the background at certain revs, which again could be a leak.

Bit of an update to this problem, i still havnt fixed it as i have been so busy, but i am taking my car into college in the next few weeks to get this sorted onece and for all, but i now have a new problem, which i am sure is associated with the original problem.  When i am accelerating and boost builds up and i get my supercharger type whine, its like it is overboosting and the ecu is cutting back, then it builds boost back up and the same thing happens, it doesnt cut out as the revs still build and speed with it, it seems the turbo wastegate opens for a second then closes and dumps all boost with it, then shuts again and boost builds to this overboost like problem and it all gets dumped again.  Its almost like a pulsing of the charge system if you get what i mean?  its fine at low to mid boost, only on WOT and high boost.  Is it just what i think it is and overboosting due to the leak and so being cut back or could i have a faulty MAP sensor?