All week I've been trying to identify my boost problem, car will not boost until 3000-3500 revs and when it eventually does it goes into limp mode.

Last 4 cars have been vag tdi's so I know this will be vac/air leak related, it has same symptoms as boost leak, vac leak, sticky veins etc.

 

So after a few days of vcd's and checking dpf, sensors, egr, manifold actuator, boost solenoid and pipes are fine I checked the turbo actuator.

Easy test on the cr tdi's... start car, take vac pipe on and off actuator and watch if actuator rod moves, which it did but not enough.

So as I don't no smoke machine my mate blew his 'vape' fag through the actuator vac pipe and what do know, 'vape' was pouring out through where the rod exits the actuator.

 

So I'm assuming this is not normal but need your guys help just to confirm that a leaking actuator obviously needs replacing??

Any help appreciated.

 

Also if you lovely people are struggling to find an air/vac leak, them 'vape' fags are brilliant in finding the leaks.

Any comments welcome. Cheers.

It doesnt sound normal to me but I have no specific experience of having performed that test on a working actuator. The actuator has to hold vacuum though to work properly.

 

Sounds like the diaphragm will be shot. That could cause overboost. The tension spring could be shot too. 

Edited 20 July, 20178 yr by TheClient

Thanks for reply. These turbos on the cr tdi rely on vacuum to work which confuses things a little as we are blowing into the actuator and not sucking, but i'm sure its still not supposed to leak either way??

One things for sure when I replace old one I'll be cutting open actuator to see how the rubber diaphragm actually works.

Yes, ok. unless there is a valve employed in the actuator, it should hold pressure or vacuum, I would of thought.  There seems to be a lot of information in here and the links within it, even if it is not your exact engine it also refers to the operation being opposite to earlier generation models:

 

http://www.myturbodiesel.com/wiki/vnt-turbo-actuator-adjustment-repair-replacement-on-tdi-engine-mk4/

 

You could buy or ideally borrow a hand vac pump, the cost is probably similar to the actuator though. 

 

Maybe someone else who has played around with this on a TDI, will know from actual experience.

Turbo actuator was to fault. Back to full boost again.

£80 for reconditioned one also sending old one back.

£60 fitting by a VW technician out of hours, all good.