Transportwer T5 2004 AXE 128kw engine turbo problem .

[Sunny43.5]

Hi I decided to put this one out here in case someone has an answer or a suggestion , our van has had an issue of what has been logged as turbo overboost . Is this an issue that can be discovered by a scan ie the ACTUAL part that is causing the overboost . First thing in the morning when cold it takes around 30 metres before it gets going properly seems to lag . When its warmed up its perfect , but then on rare occasions I can be driving along the highway at 100 kays and you go to accelerate a bit and you can feel the engine sort of lag or hesitate and then it goes into limp mode a quick flick to neutral switch on and off quickly and its fine again . I want to sell this van but don't feel comfortable selling it with this niggling fault . I have replaced the MAF sensor and the N57 valve but it still does it . Any part of the vacuum system that needs to be checked , some time back I did find a tiny split at a junction but since repaired . Thanks in advance guys .

[TDIfan]

Those symptoms you've described could be caused by a sticky vane lever or a sticky vacuum actuator
Probably due to age and the soot/oil build up at that area
VNT turbos are quite known for that
Have a look at your turbo see if it's your case

[gldgti]

bet diagnosis ethod would be to connect an analogue boost gauge somewhere to double check the boost signal, and also log the boost whilst driving with VCDS.

[Sunny43.5]

The turbo was replaced and completely cleaned and checked before fitting , it came from a van that was on the road and running perfectly . So I need to check the vacuum actuator .

[Sunny43.5]

Can anyone tell me is this valve / connector supposed to be orientated a particular way it has an arrow pointing towards the engine it is the main vacuum line for the brakes and Turbo pipes . When the turbo was replaced this same workshop refitted and split the small hose on this connector , I discovered this and cut the bit out and refitted . Now I am not sure if these same people put this valve in the right way any clues ?

[Umai Naa!!]

Pull it off and blow through it.

Restricted side should be towards the brake booster.

Overboost generally suggests that the wastegate on the turbo is not controlling the boost correctly. There should be a vacuum line off the wastegate diaphragm that should be hooked up to that junction. If it's split or not connected, the turbo will overboost.

Also check that the freeplay in the actuator rod on the diaphragm is not excessive. If it's all loose and wobbly, it won't respond as quickly as the ECU expects it to, therefore logging an overboost code.

Been there, done it. New exchange turbo from Volkswagen fixed it.

[Sunny43.5]

Thanks Umai I will check the valve not sure where the actuator you referred to is I can see something down over the top of the engine on the turbo side , or is it the one on the intercooler pipe ? There are so many little valve and junction pieces just at the centre top of the engine mounted on the firewall , its a bit hard to know how many of those are working with the vacuum system as well which could effect the turbo .

[Umai Naa!!]

Anything coming off the fat plastic pipe from the brake booster, as shown in your pic, will be part of the vacuum system.



That prominent round thing off the side of the turbo is the wastegate diaphragm. It is on the bottom side, when fitted to the car. You can see the linkage from it for the variable vanes from up top. Grab hold of it, and see how much play there is. A little bit is ok, but a lot is no good. Also make sure there is a vacuum line going to the teat on the diaphragm.

[Sunny43.5]

Okay have checked the valve its is the right way around [no brakes told me that pretty quick ! ] now there appears to be a moving arm partially seen from above on the engine side of the turbo it moves up and down when pushed appears spring loaded it feels nice and tight no sideways movement . The vacuum tube from the engine side does go to a white valve style fitting there are two more tubes connected to that as well , one goes to the turbo and the other seems to feed into another tube with what looks like a mini air filter at the end . The other various valves with electrical connectors seem to feed to the Intercooler diaphragm and also another vacuum operated fitting inside the intercooler pipe itself .There is also a vacuum storage tank there as well . I am going to get the van up on some ramps on the weekend and have a look at the underside of the turbo as I cannot see where the vacuum tube connects as its out of sight .