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How To Access Turbo to Work On

Hamad990

Passed Driver's Ed
Location
Winnipeg, Manitoba
Car(s)
2007 Golf GTi
Hello,

This is my first post on this website so please forgive any formatting issues if there are any.

So my 2007 Golf GTI has recently gave me an underboosting code (P0299) and I've decided to check the issue out myself starting with checking out the wastegate to see if its stuck open. So I pop the hood open, and remove the engine cover, but there wasn't enough space to work on the turbo, so I thought that I'll have to get under the car to get to the turbo. So the next day I jacked up the car, only to realize that I can't easily get to the turbo from the bottom either. So I've come to the realization that I'll have to remove some parts to get to the turbo, however, I'm stuck with the decision of wether to do it from the top or bottom. So I was wondering if anyone has some experience with working on their turbo, or could point me in the correct direction with a video that could help me out. Also any other suggestions for diagnosing the underboosting code would be appreciated.

Thanks in advance!
 

1131

Passed Driver's Ed
If the wastegate arm is the only thing you're interested in, you can reach it from the top. You may need to put a knee up on the lock carrier. You can feel around for it behind the turbo's upper heat shield. It has the benefit of being the only thing that's rod-shaped back there. If, OTOH, you want to feel around the compressor wheel, then you'll have to separate the cat from it. I think it would be better to do that from the bottom. You'll just need to remove the turbo's lower heat shield to access it. Here's a guide I've used to replace my turbo. But since you're only inspecting and not replacing just yet, you should be able to start at step 21 and follow to step 26.

https://www.pelicanparts.com/techar...Your_Turbo/63-ENGINE-Replacing_Your_Turbo.htm

If it's not the turbo, then you have a leak somewhere. I'd smoke test it. In fact, it might be easier to start with that.
 

Hamad990

Passed Driver's Ed
Location
Winnipeg, Manitoba
Car(s)
2007 Golf GTi
If the wastegate arm is the only thing you're interested in, you can reach it from the top. You may need to put a knee up on the lock carrier. You can feel around for it behind the turbo's upper heat shield. It has the benefit of being the only thing that's rod-shaped back there. If, OTOH, you want to feel around the compressor wheel, then you'll have to separate the cat from it. I think it would be better to do that from the bottom. You'll just need to remove the turbo's lower heat shield to access it. Here's a guide I've used to replace my turbo. But since you're only inspecting and not replacing just yet, you should be able to start at step 21 and follow to step 26.

https://www.pelicanparts.com/techar...Your_Turbo/63-ENGINE-Replacing_Your_Turbo.htm

If it's not the turbo, then you have a leak somewhere. I'd smoke test it. In fact, it might be easier to start with that.

Thanks so much! I think ill actually start with the smoke test first if you think it's easier to do, hopefully its just a leak then
 

1131

Passed Driver's Ed
Thanks so much! I think ill actually start with the smoke test first if you think it's easier to do, hopefully its just a leak then

Easier still than doing a smoke test would be to check your (front) PCV. That is arguably the most common failure on our cars. I may as well mention it before ROH jumps in and says it. Other points of contention would be the DV and (rarely) the N75 or N80.
 
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3BallUG

Passed Driver's Ed
Location
Jerz
I know you're not to this point yet but I replaced mine last year with a buddy for the same underboost problem diagnosed by two reputable shops and I still have the problem. Sooooo...

It took about 7-8 hours. Both of us had never done one before and we had a lift. But yes if you need to check the arm it can be done from the top. There's a shield back there that if removed will give you much better access but it's not necessary.

Replacing it is not easy but it can be done in a weekend. Pack plenty of patience and make sure you have all the right tools if you decide to tackle the job yourself and try to recruit a friend. I watched a video and I printed out a step by step instruction pdf to refer to along the way. It helped big time.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
People have already mentioned the most common causes for low boost.
They are PCV, DV, and boost plumbing or even intake manifold leaks. Also, the "N75-charge pressure control valve" can fail or crack. When the N75 fails it usually causes weird boost but is often less boost than normal when failed. If you do not have a boost gauge, one may not notice the boost build-up dropping more and more over time.

If you haven't done the smoke test yet:
Easiest one to rule out is the PCV. Disconnect the PCV's corrugated tubing at the intake manifold, wipe the oil from the disconnected end, and blow into it with force. If it seals, then the PCV is not losing boost.

Next is visually inspect for leaks at every connection for boost plumbing from the turbo outlet to the throttlebody. Look for oil seeping from the connections. Replace seals if necessary or reattach hoses if found to be disconnected.

Access and remove the DV and inspect the DV's internal piston/diaphragm. Plan to replace it and have a spare on hand.

Still if coding low boost: Smoke test it. Or pressure test with soap spray. When pressurized, spray all of the boost plumbing connections between the turbo outlet to and including the intake manifold. Some leaks aren't seen when you visually inspect it...including intake manifold seams coming apart.

Lastly; remove the front right wheel arch liner and disconnect the N75 wires...the N75 is mounted on the turbo. Test the N75 resistance. If below 25 ohm...replace the N75. The N75 can crack and I am unfamiliar with the behavior of a cracked N75 as mine only lost some resistance and boost would build as much when it was found to be at 22 ohm. VW spec for the N75 is 20 to 30 ohm, but I was told replace it when under 25 ohm.

You can reach the wastegate actuator(WGA) from underneath. I really do not think it is the problem unless the rod or WG linkage has come apart. I have adjusted my WGA preload a number of times. I Installed the Forge WGA. I replaced the N75. All while the turbo is mounted. I have a K04, so the DV is relocated. Here's my vid to show how to see the WGA and WG linkage...must remove the axle's heat-shield:
 
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Hamad990

Passed Driver's Ed
Location
Winnipeg, Manitoba
Car(s)
2007 Golf GTi
Easier still than doing a smoke test would be to check your (front) PCV. That is arguably the most common failure on our cars. I may as well mention it before ROH jumps in and says it. Other points of contention would be the DV and (rarely) the N75 or N80.
I know you're not to this point yet but I replaced mine last year with a buddy for the same underboost problem diagnosed by two reputable shops and I still have the problem. Sooooo...

It took about 7-8 hours. Both of us had never done one before and we had a lift. But yes if you need to check the arm it can be done from the top. There's a shield back there that if removed will give you much better access but it's not necessary.

Replacing it is not easy but it can be done in a weekend. Pack plenty of patience and make sure you have all the right tools if you decide to tackle the job yourself and try to recruit a friend. I watched a video and I printed out a step by step instruction pdf to refer to along the way. It helped big time.
People have already mentioned the most common causes for low boost.
They are PCV, DV, and boost plumbing or even intake manifold leaks. Also, the "N75-charge pressure control valve" can fail or crack. When the N75 fails it usually causes weird boost but is often less boost than normal when failed. If you do not have a boost gauge, one may not notice the boost build-up dropping more and more over time.

Thanks to all of you guys for the help! I apologize for the late replies, but I wasn't getting any notifications at my email, so it was only till now that I decided to check out the forums, and happened to see if there were anymore replies.
I'll be honest, I haven't been able to touch the car, I've been really busy with work, and as a result I've been forced to drive the car with the underboosting. However I should be able to check everything out on Wednesday, if not, I've also got some of the next day to keep on working it. I'm hoping it won't come down to needing to replace the turbo, but if it does, where would be my best bet to get a replacement K03?

Once again I appreciate the help from you guys, and I'll keep you guys updated.

Also, is there a specific way to mention users without quoting their post?
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Where would be my best bet to get a replacement K03?
Also, is there a specific way to mention users without quoting their post?
Replacement K03: They are near $900 for a new Borg Warner, $1300 for a Borg Warner with a VW/Audi badge, and less for rebuilds and clones.

To mention users: I quote or multi-quote and edit/reduce their post. Like I did ↑ with yours. Though you have to leave something from their post.

Or you can copy their user name and paste it...
Hamad990
ROH ECHT
1131

...etc.
 

Hamad990

Passed Driver's Ed
Location
Winnipeg, Manitoba
Car(s)
2007 Golf GTi
ROH ECHT
Thanks for that.
I was finally able to take a look under the hood and after looking at the possible causes here's what I came up with.

-Wastegate actuator: like you guessed, that was fine. The only reason I mentioned it in the first place was because a friend of mine had his rusted open, so I thought that it would be a good place to start.
-N80: I didn't really find anything wrong with that (to be fair, I didn't know exactly what to look for) the hoses and clamps both seemed fine.
-N75: I quickly realized that I wouldn't easily access this so I decided to leave it for another time.
-Smoke/Soapy tests: I didn't have a smoke generator on hand I decided to leave that for another day, and I ended up deciding to do the soapy water test at the same time as well.
-PCV: This was the only thing that seemed wrong to me. I did the blowing test you mentioned, and I was unable to blow air in at all no matter how hard I tried. I included a picture of where I blew into just to make sure I was doing it right.

One thing that confused me was that after checking the N80 and the PCV, I decided to rescan the car and go for a drive. When I scanned the car I noticed that the underboosing code was gone and was replaced by code P2178 (System too rich off idle). After some aggressive driving (that's how the underboosting code was triggered for me in the first place) I noticed that the car was pulling harder than it used to when I'd floor it. After the drive, I scanned the car to see if the code would trigger again but it didn't. I guess the issue is something related to the N80 or PCV? I was going to replace them both regardless of if they were good or not, since it seems like they haven't been replaced in a long time, plus I'll be able to make note of when the next time I should replace them is.


IMG_1381.jpg


So the red circle is the end I opened up, and blew into. So I was blowing into the PCV. I was completely unable to blow any air into the PCV regardless of how hard I was blowing
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
OK...I am writing all of this only because I do not know exactly how all was done.

Here's my Testing the N80 vid...testing the vacuum direction (to the intake manifold/first test I do in the vid) is most important:

To do a soap/water solution...you need to pressurize the bits you plan to test. Using a shop-vac set for blowing can work if attached to the intake or turbo inlet. Because you need the air inside to be coming outward to make the soap solution bubble.

The PCV test you did was done correctly and shows it is not losing boost there. As long as it seals when you blow into that tube...then the boost is not leaking. Just beyond and below the elbow at the end of the arrowhead is the check-valve that is supposed to close when in boost.

The check valves in the PCV can accumulate crud on the valve and the same happens inside the N80. The PCV can be removed and given a Fuel/petrol bath. The N80 has a screen that can become plugged and build-up happens on the inner valve as well. You can clean the N80 the same, with fuel, but they are less than $15usd to replace.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI

3BallUG

Passed Driver's Ed
Location
Jerz
Let us know if you find a solution to your problem. I'd sure as hell would like to know what it turns out to be. I've had this underboost issue for over a year. Comes and goes.
 

Hamad990

Passed Driver's Ed
Location
Winnipeg, Manitoba
Car(s)
2007 Golf GTi
3BallUG Ill definitely update this thread if it comes back or not, but the code hasn't triggered since last time, although the System Too Rich code is still there. The only things I did was take off the N80 and PCV and clean the area surrounding them with a rag, and that seemed to fix the issue. I'll still be replacing them, as well as inspecting/ replacing the diverter valves since I've heard that they can be really finicky. Ive also got plans to smoke test it, but I don't have a proper smoke machine to help me so I might just use a vaper friend and hope that'll be good enough to find one if there even is a leak.
 
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Hamad990

Passed Driver's Ed
Location
Winnipeg, Manitoba
Car(s)
2007 Golf GTi
ROH ECHT Thanks for the link! I think this'll be my new go-to for possible solutions to my issues before heading on to the forums. I'm currently thinking of just replacing the PCV, N80, and Diverter valves since they probably should be replaced.

For the engine running rich code, I cleared it but it was triggered later that day when I drove the car. I haven't had a chance to look at the possibilities, but I should be able to take a look at it tomorrow
 

3BallUG

Passed Driver's Ed
Location
Jerz
Good to hear you're having better luck than I am. I'll keep an eye on this thread. If I come across any useful information I'll be sure to report back.
 
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