turbo not working

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
On the way home last night, my 2000 Jetta (390,000 miles) suddenly lost power. I managed to limp it home, but it was an absolute SLUG. I never got a CEL and didn't go into limp mode, but power was about 1/3 of norma (maybe even less than that)l. It was "manageable" downhill or on flat ground but it struggled with hills so bad, even on the slightest incline, that I could only manage to get up to about 20 mph with it to the the floor in 2nd gear.

A similar thing (same symptom) happened when I first bought it several years ago and was on the way home. That ended up being a hole was rusted in the vane actuator. That was around 140,000 miles and it has been good ever since I replaced it. I also replaced all vacuum lines during that process.

Starting with the easiest to check and most likely problems, what all should I check when I get home tonight?

Unfortunately I do not have VCDS.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
Make sure no boost pipes have popped loose. Check the actuator (again). It should hold vacuum and start moving at about 3-5hg and be against the stop at 18hg (with a mity vac). Check all the vacuum hoses. Finally if all that checks out you're probably looking at sticky vanes.
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
If you shut off your car and start it back up is your power back? If yes then yes you did go into limp mode. You don’t always get a CEL.
Do as Tdijarhead suggested.....
 

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
No, power does not come back after cycling the car off and back on.
The vane actuator moves as it should (when I apply vacuum), and at the correct vacuum.
I can manually move the vanes with its running and it will develop boost.
I can't find any vacuum leaks, but I "could" be missing something.
The vacuum pump is working.
The reservoir egg is good, but f I disconnect the vacuum line from the egg, the system will not hold vacuum with the pump on. It will start developing vacuum, but quickly bleeds off. Is that normal, or do I have a leak?
Could the N75 valve be the problem, and is there a way to test it? I'm not sure if the system SHOULD maintain vacuum or if there's a leak that I can't find.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
The one thing I forgot was the n75 valve. Yes it should hold vacuum if you test it with a mity vac at the port that leads to the actuator.
 

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
The one thing I forgot was the n75 valve. Yes it should hold vacuum if you test it with a mity vac at the port that leads to the actuator.
Is that valve something I can get at Autozone or am I gonna have to order it? I can't find it on their website. What is the generic name for it?
 

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
The one thing I forgot was the n75 valve. Yes it should hold vacuum if you test it with a mity vac at the port that leads to the actuator.
The valve will NOT build any vacuum at all (none) when I apply vacuum to the port that feeds the vane actuator. That is with the other 2 lines still attached to their respective ports.
When I unplug the other 2 lines and cap off the ports, it will build vacuum momentarily but then quickly leaks down.
Can I assume that the valve is bad?
 

shoebear

Veteran Member
Joined
Aug 1, 2002
Location
Colorado Springs, CO
TDI
1998 Jetta, 2003 Jetta Wagon, 2005 New Beetle, 2013 Sportwagen
I don't know if the N75 valve is bad or not, but I keep a spare just in case. Check your local parts stores, but I think you are unlikely to find one. The VW part number is 1J0906627A, and Pierburg makes a quality replacement, part 7.02184.01.0. You can get this from idparts for $35+$5 shipping:

https://www.idparts.com/pressure-converter-n75-for-turbo-alhb55-1j0906627a-702184010-p-447.html

You can probably find N75 diagnostic instructions by searching. Here are a couple of likely-looking ones to get you started:
http://forums.tdiclub.com/showthread.php?t=154871
https://www.audizine.com/forum/showthread.php/297974-How-do-i-diagnose-bad-n75-valve
https://forums.tdiclub.com/showthread.php?t=187540
 
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wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
I would tee the gauge into the line from the N75 to the actuator.
Starting the car you should get vacuum, 10 inches or so iIrc.
The actuator should move.

I had a long hose to put the gauge in the car and found the vacuum to the actuator drops when I started driving.

I don't think the N75 holds vacuum internally 100%. (My tests with only a few)

Last, the lowest port (iIrc) should go the the bottom of the air filter box.
If that port is blocked with dirt it raises havvoc.
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Just for $hits and grins, how is your brake booster hard plastic pipe?
These have a tendency to crack on the inside radius causing a leak, usually resulting in hard brakes. Worth a shot.
Also tee into your vacuum pump and see what kind of vacuum it’s pulling. I believe it’s supposed to be around 25 inhg. The nipple is famous for coming loose too.
 

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
I would tee the gauge into the line from the N75 to the actuator.
Starting the car you should get vacuum, 10 inches or so iIrc.
The actuator should move.

I had a long hose to put the gauge in the car and found the vacuum to the actuator drops when I started driving.

I don't think the N75 holds vacuum internally 100%. (My tests with only a few)

Last, the lowest port (iIrc) should go the the bottom of the air filter box.
If that port is blocked with dirt it raises havvoc.
T'd into the line between the solenoid and the actuator, I have 20 psi (iHg) at idle. When I give it throttle, it tries to drop (which should close/tighten the vanes and raise boost, if I understand how it works), but it only sputters and drops to about 15. Correct me if I'm wrong, but shouldn't it drop to near zero?
I don't have anyone home to help right now, but yesterday I checked for actuator travel and it only moves (opens the vanes) when you start it. It will not move the actuator as you raise RPM's like it should. I belive because the vacuum is not being modulated properly.
You are correct that the other (bottom) port goes to the sidd of the air box. That line also T's and goes to another solenoid that looks similar to the ,
N75. The lines are clear all 3 directions. What does that other solenoid do/control?
 

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
Just for $hits and grins, how is your brake booster hard plastic pipe?
These have a tendency to crack on the inside radius causing a leak, usually resulting in hard brakes. Worth a shot.
Also tee into your vacuum pump and see what kind of vacuum it’s pulling. I believe it’s supposed to be around 25 inhg. The nipple is famous for coming loose too.
The brakes feel the same as they always have.

At idle, the vacuum pump develops 25 iHg within 3 seconds and increases to around 30 within another 15 seconds.
 

commanderjjones

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Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
So with the above being said, any other ideas on what to check before I give up and take it somewhere???
There is only one place that I feel are TDI experts, and they are 65 miles away....and are a$$holes. So I'd much rather attempt to fix this myself.
None of the auto parts stores around here have the correct N75 solenoid, but I'll order one if you guys think that'll fix it. I went into town to get one that "supposedly" fit, but it only had 2 ports and not 3......and I wasn't sure if a T would make it operate properly.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
For troubleshooting, you can swap the N75 with the N18. Not sure if these cars actually boost much without a load on. If you drove it with the gauge on the tee, and it didn't drop towards 0 under full load, just get a new N75.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
When the n75 is off the car I can plug the two other ports with my fingers and put a vacuum on the actuator port and it will hold vacuum.

Your car will not build boost if it’s not under load. Swap the n75 and n18 around. The n18 looks just like it and is located about 6 inches to the left. Then take your car for a drive.
 

commanderjjones

Veteran Member
Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
Well, its wasn't the N75 solenoid. My driveway has a slight incline and I can't even back out of it.
So what do I check next???
 

commanderjjones

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Joined
Jul 1, 2011
Location
Harriman, TN
TDI
2000 Jetta GLS, silver 5-speed
Well, I've been through the "low power/limp troubleshooting guide" and none of those seem to be my problem. However after putting it up on ramps last night, I did discover that I have a BAD exhaust leak. Where the flex pipe attaches to the hard pipe directly out of the turbo (about 10" downstream of the turbo), that joint is basically broken in half. Would a bad exhaust leak cause my turbo to not work, even though the leak is downstream??? It isn't in what I would call "limp mode", cycling it off and back on doesn't restore the power, and I have never gotten a CEL.
 

flee

Veteran Member
Joined
Sep 19, 2011
Location
Chatsworth, CA
TDI
2002 Jetta GLS wagon
Well, I've been through the "low power/limp troubleshooting guide" and none of those seem to be my problem. However after putting it up on ramps last night, I did discover that I have a BAD exhaust leak. Where the flex pipe attaches to the hard pipe directly out of the turbo (about 10" downstream of the turbo), that joint is basically broken in half. Would a bad exhaust leak cause my turbo to not work, even though the leak is downstream??? It isn't in what I would call "limp mode", cycling it off and back on doesn't restore the power, and I have never gotten a CEL.
No, it wouldn't.
See what your MAF is doing requested vs actual with your VCDS.
Or just unplug it and see if the power improves.
 
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Vince Waldon

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Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Well, I've been through the "low power/limp troubleshooting guide" and none of those seem to be my problem.
A key step in that guide is using a hand vacuum pump to confirm the actuator starts moving at about 3-5 inHg, and gets to the stop at 18 inHg.

Were you able to confirm those numbers?
 

shoebear

Veteran Member
Joined
Aug 1, 2002
Location
Colorado Springs, CO
TDI
1998 Jetta, 2003 Jetta Wagon, 2005 New Beetle, 2013 Sportwagen
A key step in that guide is using a hand vacuum pump to confirm the actuator starts moving at about 3-5 inHg, and gets to the stop at 18 inHg.

Were you able to confirm those numbers?
Tdijarhead suggested that test in post #2 of this thread, and commanderjjones confirmed that the turbo behaved per spec in post #4. Jones was a little sloppy in his confirmation wording and didn't specifically mention that the actuator hit the stop at 18 inHg, but jarhead specified that and Jones said it worked correctly.
 
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