Sticking actuator or faulty N75 solenoid?

Palka3

Member
Joined
Dec 21, 2017
Location
Jackson GA
TDI
2002 Jetta TDI
I was driving my Jetta to a meeting. After filling up with diesel I was merging onto the interstate. While merging onto 75mph traffic I felt the car jerk slightly. The Engine light came on shortly after that. I turned around and swapped vehicles.
A Scan stated it was the Turbo. I didn't think so because the car never went into "limp mode"
I've read thru the forum and narrowed it down to the vacuum lines. I replaced the original vacuum lines (180K miles) to both EGR(N18) and boost(N75) valve. The actuator tested OK under vacuum. The linkage at the turbo was lubricated while I was there. The engine light went away (on its own) after the vacuum lines were replaced.
Yesterday the same thing happened on a 275 mile trip. I noticed it occurs around 70-75MPH when merging or climbing a hill or passing another vehicle where boost is needed. It's almost like the actuator or boost valve is sticking when it gets to a certain value. I don't have a EGT or boost gage to determine if there is a change before of after this event.
Any help would be appreciated.
 

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
What was the actual DTC(digital trouble code)? Chances are it is still stored in the ECU.
 

Palka3

Member
Joined
Dec 21, 2017
Location
Jackson GA
TDI
2002 Jetta TDI
P0235 as read from AutoZone. The funny thing is I was taking the car to a friend that has a VAG COM when the code cleared itself. I suspect there was a vacuum leak and it took a little time for the ECM to reset and clear the code.
 

Palka3

Member
Joined
Dec 21, 2017
Location
Jackson GA
TDI
2002 Jetta TDI
To clear up my last post. I still have a check engine light.

I've read that you can clean the solenoid with carb / electronic contact cleaner. Where would you be spraying?

Each port?
Isn't that just cleaning both sides of a diaphragm? Maybe the solenoid is sealed. If not, then the cleaner might loosen up the rod that controls the operation of the diaphragm.

The other location to spray would be the electrical connections. Maybe the contact points are dirty and giving a false signal to the solenoid.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
A light cleaning of the N75 could help, normally they don't get dirty, takes some contaminent into the vacuum system.

From Ross Tech wiki-
Possible Causes
Hoses/Pipes incorrect connected, disconnected, blocked or leaking
Charger Pressure Control defective
Solenoid Valve for Boost Pressure Control (N75) defective
Turbocharger defective
Possible Solutions
Check Hoses/Pipes to/between Components
Check Charge Pressure Control
Check Solenoid Valve for Boost Pressure Control (N75)
Check turbocharger
 

adjat84th

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Joined
Dec 13, 2008
Location
Virginia Beach, VA
TDI
'01 Jetta TDI/'15 Golf TDI
Get a MityVac or similar and apply vacuum to the actuator and check to see how smooth the rod moves. If you apply full vacuum till it hits the stop and then release, it will give you a good indication if that's your issue. Sticky vanes can certainly cause overboost.
 

wonneber

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Oct 12, 2011
Location
Monroe, NY, USA
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2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
I've read that you can clean the solenoid with carb / electronic contact cleaner. Where would you be spraying?

The other location to spray would be the electrical connections. Maybe the contact points are dirty and giving a false signal to the solenoid.
I took the N75 off, sprayed a bit of penetrating oil in each port, then shook it and lightly blew air to each port.
The car did seem more responsive for several days.
I did finally replace it.

I've read you use dielectric grease in the plugs and sockets.
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
Good thing you replaced it . Penetrating oil would have most likely destroyed the diaphragm over a short time.

I almost never use dielectric grease except maybe on light sockets because most automotive connectors are waterproof.
 

VincenzaV

Veteran Member
Joined
Apr 25, 2015
Location
New Hampshire
TDI
2004 Jetta Wagon
PLEASE wear eye protection if you are taking of the N75 and spraying it to clean it with anything (compressed air/brake cleaner). I did that to mine and in a "I don't NEED no safety glasses man-moment" got blasted by carb cleaner in the eye, Not fun, thankfully no permanent damage.

On the testing of the actuator, the advice of using a mityvac or equivalent is golden. But before you buy/borrow one, get under the car and move the actuator lever with your finger or a screwdriver (its a strong spring! but you can do it). I heard a "crunch-crunch-crunch" rust sound as I was moving it with my hand and knew instantly:

1. Regardless of if my vacuum system did/did not have a leak, the smart actuator HAD to be replaced.

2. The N75 SHOULD be replace (since rust contamination was in the system), didn't want to kill the new actuator in a few weeks/months

3. The vacuum lines SHOULD be replaced

I did all three.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
"I don't NEED no safety glasses man-moment" got blasted by carb cleaner in the eye, Not fun, thankfully no permanent damage.
Not all of us are as bright as you
*puts ear up to the end of the garden hose tell if the water is coming
>ear infection for 3 months
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
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2006 BRM Jetta
2. The N75 SHOULD be replace (since rust contamination was in the system), didn't want to kill the new actuator in a few weeks/months
Never heard of that one before. So how exactly does "rust contamination" get into a vacuum system? How did the rust get contaminated?
 
Last edited:

flee

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Joined
Sep 19, 2011
Location
Chatsworth, CA
TDI
2002 Jetta GLS wagon
Never heard of that one before. So how exactly does "rust contamination" get into a vacuum system? How did the rust get contaminated?
IDK if it's really a thing but it's not that hard to imagine a failed (rusted open)
actuator letting in some debris, including rust particles.
As far as replacing the N75 though, I've had good luck blowing out a bit of debris
just using compressed air. Original one from 2002 still working.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Never heard of that one before. So how exactly does "rust contamination" get into a vacuum system? How did the rust get contaminated?
Broke vac pump can let in some crankcase gas, half cleaned EGR,n75,etc. could introduce rust bits, unconnected vacuum tubes. Actuators rust out but usually stay clean on the vacuum side.
I thought this was odd as well, but a few have reported various contamination of the vacuum system.
 

VincenzaV

Veteran Member
Joined
Apr 25, 2015
Location
New Hampshire
TDI
2004 Jetta Wagon
The actuator rusted out, pure and simple.

As far as the N75, Not sure how, but after it shot at my eye, I was able to use compressed air and hit the N75 and see little rusty bit in my hand from the N75.

Not sure if actuator rusted through inside completely (could explain the crunching rust noise), or were it came from.

It's all good now though!:D
 

JB05

Top Post Dawg
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Oct 20, 2005
Location
Il.USA
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Golf,2005,anthracite blue
My N75 was heavily contaminated with powered rust particles sucked in from the turbo actuator which I cut open. The diaphram was completely rotted out.
 

Palka3

Member
Joined
Dec 21, 2017
Location
Jackson GA
TDI
2002 Jetta TDI
UPDATE:
I replaced all hose lines. I now have color coded hoses (Yellow = vacuum; Blue = EGR; Green= n75) I replaced the n75 valve. The actuator on the turbo moved as designed. Vacuum applied to actuator operated the arm as designed. Yesterday I made a 500+ mile trip and everything was GREAT!...except for the last 60 miles. The engine light came on while on the interstate. No signs or symptoms of trouble...I just glanced at the dash and the MIL light was on. I lost all that power I was so proud of having earlier. Before the MIL light I could touch the (gas!) pedal and have instant response. Not now. It runs like a non turbo vehicle. One thing I have not changed or checked is the MAF sensor. I usually clean it as part of my 10K service. It's original (182k miles) I've read that they usually don't fail, they just wear out over time. I replaced the MAF once before but the new one caused the car to "jerk" every once in a while. I put the original MAF sensor back on and have been running on it ever since.

NEW UPDATE: I may have a bad MAF. I just started the engine and pulled the wire connector off of the MAF sensor. The engine DID NOT stop. I'll put a scanner on it, change the MAF is necessary and get back. In the meantime...any other ideas on what could be the culprit would be appreciated.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
The code would give a clue.
Drive the car with the MAF unplugged, if it performs the same it could be the MAF, but other factors come into play.
Did the new actuator get adjusted?
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
what hoses did you use? brand, purchase location?

cheep hoses can react with oil, crimp under vacuum, and blow off or crack under boost.
 

Palka3

Member
Joined
Dec 21, 2017
Location
Jackson GA
TDI
2002 Jetta TDI
I used silicon hoses that were leftover from other projects. I used small tye wraps to ensure a good seal at each fitting.

UPDATE [/B][/B]: I replaced the MAP sensor that was causing hesitation with a new one. The car runs like a new car. I completed another 500 mile trip Monday without ANY problems except when I had to back off the "go pedal" a few times because I was doing 85+ on the interstate without realizing it. The power in this "little engine that can" is amazing.

The bottom line in my case is that the scanner code did not require me to replace the turbo like the part person stated but replace the N75 valve, hoses to the valves and MAP sensor.
 
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