Driving last night, overtook a car, no silly speed or boost, slight squeal then bang and total loss of power.

Thought oh no, not turbo again (like last year - almost to the year!).

Drove on for a bit, still no boost, but no silly revving (like last year).

This morning - boost pipes all seem good. Oil level is good. No oil in intercooler pipes.

Took off tip and downpipe. Can spin both wheels in the turbo. No resistance or play. spin one, the other spins.

Not sure what else could cause total loss of boost? Vac box?

Thats a really odd one - especially if the turbo is fine (thank goodness!)

What was the 'bang' like? Where did it seem to come from? Metallic 'bang' or more dull?

You've definitely checked all the pipes properly? Your description sounds like mine did when it blew a boost pipe.

Yeah, just been on phone to Turbo Dynamics - they seem to think turbo is fine. Need to get bumper off and check the intercooler - otherwise not sure what it could be.

If VNT mechanism is broken, will that cause no boost. i.e. if the VNT mechanism is closed is no boost produced?

I have the same symptoms to as when I had dodgy wiring on the MAP sensor, i.e. no boost but still driveable and a slighly louder exhaust note.

But this time there was a bang - so somethings broke!

Intercooler and pipes are all fine...

Yeah, the VNT moves to assist spool up, then changes as it gets up to speed. Check the actuator pulls shut when the car starts and stays closed at idle maybe?

Yeah, I know how the VNT system works and all that in normal operation, just wanted to confirm that no boost is produced if there is no vacuum to the actuator. Therefore no boost. Which I assume must be the case as when I had the problem with the MAP sensor wiring.

I can move the actuator with my hand with some resistance and its smooth and it springs back into rest position. Maybe its an internal VNT problem...

Will look at the operation of the actuator when starting and at idle but need a helper! And she is at work lol. And its ****ing down!

Edited 8 March, 201313 yr by trebormint

Yeah, to check the box works, it'll apply vacuum on the actuator and pull it shut at idle. No vacuum leaves the VNT open and boost builds really slowly - kind of a safety feature. If it was the other way, youd over boost very easily!

I'd offer my help, but im sat at my desk at work

Do you have VCDS? Can check actuator movement via that mate

Yeah, to check the box works, it'll apply vacuum on the actuator and pull it shut at idle. No vacuum leaves the VNT open and boost builds really slowly - kind of a safety feature. If it was the other way, youd over boost very easily!

I'd offer my help, but im sat at my desk at work

lol, that's no excuse!

Need to check operation of actuator upon start up and idle and go from there. Just the noise I heard is worrying me! Might just have to get the turbo off :(

Do you have VCDS? Can check actuator movement via that mate

No VCDS :(

lol, that's no excuse!

Park outside my office window and i'll shout out and pass tools if you like?

You can test the closing actuator rod on your own. just check that its open, then start car and see that its pulled tight against the stop screw, and holds shut.