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This article shows how to test or replace the turbo actuator on a TDIengine (vacuum actuator)
All mk4 and newer VW TDI Jetta, Golf, Passat, and New Beetle use vacuum actuated rodto move the vanes inside the VNT turbo. A sticky turbo actuator can causelimp mode by not moving the vanes as the car computer expects. Dealersusually replace the entire turbo because they make more money and it increases the chance of fixing the symptoms in 1visit. This is because the vanes inside the turbo or the vane control ringinside the turbo can also be bad and cause the same symptoms.
The VNT actuator looks like a wastegate can and uses a lever tomove the VNT vanes inside the turbo. VNT actuator and wastegates are similar in location andappearance so don't getconfused if you see the term wastegate used instead of VNT actuator. Thebiggest difference between them is that a wastegate canuses pressure to work and is found only on non-VNT turbos. The VNT actuator uses vacuum to suck its rod in. Related links: 1000q: fixing limp modeand 1000q: constant low power or can't rev.Also see 1000q: ALH/BEW turbo removal and 1000q:turbo vane cleaning.
It's possible to adjust the VNT rod to adjust its movement but before youtry this, carefully check and replace all vacuum lines and otherpossible maintenance items. If it was working fine before, do not adjustthe VNT rod. Only adjust the VNT rod if it was out of adjustment before oryou are modifying the turbo or turbo setup. Adjusting it when it doesn'tneed adjusting will not improve turbo response or fuel economy and could causedangerous boost spikes or lack of response.
Other non pumpe duse mk4 TDI engines are similar. 2004-2006 mk4pumpe duse 1.9L TDI, 2005-2006 mk5 Jetta, and 2009+ common rail 2.0L TDI use an actuator with a sensor to see rod position.A common problem with these is broken wiring at the actuator. Carefullyinspect the wiring if you have a 2004+ Jetta/Golf/NB.
FOR THE BEW ENGINE, see 1000q: BEW actuator replacement.
2004-2005mk4 Passat TDI use the non-sensor can.
Garrett (GT) and Borg-Warner (KKK) turbo actuators work in different directions. Garrett actuators suck in the rod with vac vs. push out the rod with vac. My mk5 BRM engine Borg Warner actuator pushes out starting around 3" vac and is fully extended around 17-18".
VW Touareg and Audi Q7 use anelectric actuator for the turbo so the testing and diagnosis is completely different.
If you find the tips on this page helpful, please use the donation button at the top so that I can continue to keep publishing great articles for free. The Bentley service manual is about $80 and doesn't even mention this repair - it just tells you to replace the entire turbo! This page has videos, color pictures, and greater detail. I know it's saved many people from a much more expensive repair. Thanks in advance!
How the VNT turbo actuator should work
The lever on the outside is welded to a lever inside the turbohousing. This is how it moves the VNT vanes. See the below videos tosee how smoothly and free the lever should move. It should not stick orbind at all. Vacuum is being applied to the can, not pressure. Whenthere's no vacuum (engine off), the rod is fully extended because the springinside the can is pushing it open. As engine rpm goes up and more turboboost is requested by the car's computer, the N75solenoid allows vacuum pressure to go to the can and the rod retracts under vacuum pressure.In other words, at full vacuum, the lever should be at the stop screw (notvisible). This moves the internal vanes and gives more boost. At full rest, the rod should be fully extended but not hitting anything.Because this relies on vacuum pressure, it's essential that the vacuum lines andN75 solenoid/wiring are working and not leaking.
The lever moves a ring and the ring moves the vanes. These vaneschange the angle and speed of exhaust hitting the turbine wheel.
Here's a newer video I made. A Borg Warner turbo is shown so there's some differences with the Garrett turbo shown above but the overall operation is similar.
Again, dealers prefer to replace the entire TDI turbo and actuator as a unitbecause it costs more and because it also rules out any internal turbo/VNT vanesticking problem. Below is an example of a sticking actuator. Itholds vacuum but doesn't have full or smooth movement.
Here is a video showing good actuator movement.
Once the engine is fully warmed up, you should rev the engine high and hardon a regular basis, like when entering highway on ramps(always observe posted speed limits), to raise exhaust gas temperatures (EGT). Raising EGT will burn up and blowout carbon and soot build up out of the VNT vanes and help prevent themfrom getting stuck. Only do this once the engine is fully warmed up andlet the car cool down with a period of normal driving afterwards. The keyis both high rpm and high load. High load at low rpm or high rpm inneutral with no load will not raise EGT high enough and long enough to burn upthe soot.
Before you order a replacement VNT actuator, spray some penetrating lubricant around the VNT lever as describedbelow and go for a few hard runs. You might go into limp mode afew times but it's free and it may solve the issue if the problem is only minor sootbuildup. The problem isn't from only vane movement because if youmonitor VNT movement through VCDS, it reaches full movement at a relatively lowRPM. The key is both high rpm and high load (temperatures) to burn up and blowout the buildup. Another problem is corrosion buildup around the adjusterring inside the turbo.
Limp mode with underboost is safer than limp mode withoverboost. Have the car scanned for codes and use aboost gauge to confirm which you are getting.
Also see the TSB for VNT actuator replacement with pictures and proceduresin the exclusivecontent forum
Parts (click links to compare prices)
Note - The ALH engine (1998-2003 TDI) is a little different from the BEW engine's(2004-2006 4th gen TDI) VNT actuator because the BEW's actuator has the "G500sensor" to determine vane position. This is also called the smart actuator. See additional notes below.
1 circlip/e-clips for the actuator lever and 1 spare - no VW# available buta 1/4" e-clip should work. The spare is for when the first one fliesoff and disappears. If you know the correct size/shape, please post yourcomment in the myturbodiesel forums, thankyou!
I avoid any actuator sold by sinceit's almost certainly a cheap copycat part. I also had a bad experiencewith this seller so never again.
The Garrett part comes with a clip taped to the box asshown right.
If you have the BEW or similar engine (2004+) you needthe smart sensor actuator. There is no official VW part number for itbecause VW does not sell these separately from the turbo. Borg Warner doesn't sell them either. They can be purchased from kermatdismart VNT TDI actuator and custom modified to fit.
There is no BRM actuator available but you can make a custom bracket to attach the CBEA/CJAA actuator. It will work fine. The Borg Warner (KKK) actuator rods suck out instead of sucking in because the spring is on the other side of the rubber diaphragm.
CBEA engine turbos have an actuator available, VW# 03L 198 716 a. This should also fit CJAA engines.
First confirm bad VNT or isolate another problem
First confirm the diagnosis of a sticking VNT actuator because it could alsobe a sticking turbo VNT vane, bad n75 solenoid, or leaking vacuum line.
Have ahelper turn on the car and the VNT lever should move. If you have a VCDScable from ross tech, with the engine running, click on"engine" and then "output tests". One of the tests isN75 test cycle. This cycles the n75 solenoid, VNT, and vacuumline.
A common problem is soot and carbonclogging the VNT vanes which causes the same symptom as a sticking VNTlever. See 1000q: clean turbo VNT vanes tosee a detailed cleaning procedure.
Through VCDS, log requested boost vs. actual boost.To do this, plug in your VCDS cable to the obd2 port under dashboard, near thesteering wheel. Click on "engine". Then click on "measuring blocks"in the below screen.
Then click "up" or enter 11 to view "group 11"and graph to see the below screen. If it'snot close then this could indicate a defective or clogged VNT actuator, N75solenoid, vac lines, orsticking vanes. Here is an example of a good N75 solenoid-vac lines-VNTactuator-clean turbo. Suddenly stomping on the accelerator pedal willproduce spikes - this is normal. Smooth, normal acceleration should produceminimal spikes. A healthy ALH engine should see a spike and then see theboost settle down to about 1900 mbar. Swap the N75 solenoid with the EGR solenoid as a test toisolate a possible solenoid problem and check the vacuum lines. This willisolate a boost problem to the VNT actuator or internal vanes. To furtherisolate those, do the tests below.
First put a fewdrops of PB Blaster on the VNT lever and then go for a test drive. Thismay loosen surface rust enough to get correct movement.Youmay have to remove the rubber elbow before the intake manifold and turbo intakeplastic hard pipe for clearance. Below is a picture of the passenger side with those hosesremoved.While this won't free a seized VNT vane, it won't hurtanything either. Warm up the engine and then go for some very hard runs asdescribed above.
Here is the turbo out of the car for illustration (as if you were looking atthe back of the engine). Put a few drops of PB Blaster around thelever and circlip to help them move smoothly. (There's a heatshield aroundthe can, not pictured). If you try to press the lever down by hand, youshould feel smooth, consistent resistance from the spring inside the VNTactuator. After you release the lever, the spring should immediately push it back up to the top restingposition. Full travel from the stop is about 1cm and can be seen in theabove videos.
Follow the vac line to the N75 solenoid valve (solenoid is mounted onmiddle of firewall - look above the brake fluid reservoir). Remove thevacuum line at the N75 solenoid valve and apply vacuum to the line. Therod should move smoothly beginning at about 3-5" vac and hitting the stop at18-22". Full travel from the stop is about 1cm. You can also useyour hand (on a cold non running engine only!) to feel the rod move as you applyvacuum to it.It should move smoothly with no binding or clicking.
For reference, here are the BRM engine's (2005.5-2006 Jetta TDI) actuatorspecs: during the test, do not exceed 750 mbar. The linkage shouldstart moving at around 300 mbar and be at the end at about 700 mbar. Theactuator lift should be 10mm.
If the VNT actuator is not holding vacuum then the VNT actuator is bad (sinceyou've already checked and rechecked the vacuum lines). Replace it.
If it's binding, clicking, or not moving at all, remove the actuator rod fromthe VNT lever. This will let you isolate and test the VNT lever's movement. If it's seized then youhave to remove the turbo and clean the vanes. See 1000q:turbo vane cleaning and 1000q: turbo removalALH / BEW. When the vanes stick too much, the internal lever and ringwear into each other and stick/create play.
How to remove and replace VNT actuator "wastegate can" on VW TDIor Audi TDI and adjust the rod
It's easy to remove the actuator with the turbo on the car if you have a ratcheting wrench likethis.....
.....the rest of this article and detailed pictures are in the premiumcontent forum in this post. Please join our community today and upgrade your account to premium for only $2 here: http://www.myturbodiesel.com/account/upgrades Thank you for your support!
If you have any questions about freeing a stuck VNT actuator on your VW TDI, free to ask a question about this article at thediscussion forums.
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