Squeezing my vaccum line fixed limp mode?

V1a2s2h4

Active member
Joined
Jun 10, 2014
Location
Rochester Ny
TDI
02 VW Golf
Recently changed melted vacuum lines to fix a p0299 cel but still had random limp mode symptoms. Plugged a vaccum gage to the turbo line and at idle the n75 was drawing only 5inHg on the turbo down from the normal 17. I squeezed the line a few times and it rose back to a normal idle value. Would that indicate the n75 i shot?

I've been driving with the vaccum gage connected to the line going down to the turbo to watch the relationship between vac pull and boost. When the limp mode symptoms occur, vaccum will fall down to 5inHg and I'll get a max of 4 psi with the pedal to the floor. What happens next is what puzzles me the most, vac pressure will climb back to 25inhg But when I touch the pedal it flatlines to 0 and I get no boost from turbo.

Sometimes it takes a few restarts to get out of limp mode, but could all this be pointing to the n75?

Any feedback would be greatly appreciated.

*Update 1* stopped at a rest stop after driving 80 miles without any issue, on restart the car is reading 6inhg, down again from the 17 it should be at idle. 2 restarts and it's went back to normal and pulling away from the stop it boosted normally. Cruising at 75 the vac gage was reading a steady 13inhg, about 2 miles later it drops to 5inHg and the CEL for p0299 comes back. Still getting some boost from the turbo but nothing near it's normal.

*Update2* about 20 miles into having low boost the vac gage dropped to 0 as I attempted to pass someone. Now on no boost I shifted to neutral and did a rolling restart. 2 restarts later vac idle returned to normal and car started boosting like normal. System is holding steady vaccum as of now.
 
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Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Check the lines themselves; if they're still the original cloth-covered ones they can be severely cracked internally and you won't see it.

I replaced all mine with silicone high-temp vacuum tubing several years ago when I started getting some odd vacuum-related problems and it's been trouble-free since. Note that the big "hose" by the brake booster can crack as well and if it does it will result in low vacuum in the entire system and all sorts of resulting (and sometimes intermittent) odd symptoms.
 

Ol'Rattler

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Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
Vacuum leak. The N-75 does not draw anything it just has vacuum available to it. Get a Mitey Vac and then check that the N-75 valve is not leaking by connecting the M/V to it and pumping it down. It should hold full M/V vacuum without leaking down.

Work your way up stream to the vacuum pump. With the engine running, everywhere in the vacuum system should have the same vacuum as the pump if there are no leaks anywhere.
 
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BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
I think the squeeze-hose-vacuum-increases would be debris in the lines or very thin hose.
 

V1a2s2h4

Active member
Joined
Jun 10, 2014
Location
Rochester Ny
TDI
02 VW Golf
I've check the hoses and compared to my older Alh this 04 bew doesn't have the cloth lines wrapped lines. Rhe turbo actuator line was replaced with a silicon line, I'll do the rest once I get more. I used a hand vaccum pump to check for system leaks or any other damaged lines and didn't find any. My 02 Alh had a limp mode problem because the hoses connected to the brake booster split before the n75 vac line, so I investegated that too and everything seems in order.

Im on the fence with it being a vac leak because I feel like the limp mode symptoms shouldnt come and go after several restarts
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
I see your point about about the "vac leak" comment, but you might be missing something. IIWY, I would put a vac gauge on the farthest place away from the vac pump--anti shudder, EGR valve--to look for the real culprit. I once also had intermittent boost/vacuum and I had bad solenoids past the N75; since they open at different times and throttle positions and can cause some of your parallel symptoms. I have 1 vacuum line coming off of the connection at the brake booster, just 1. You can double check your vac pump by going directly from the vac pump to the N75 and if you have over 20" of vacuum at that point, the problem is downstream is either the solenoids and/or the vac hoses running towards the passenger side of the engine compartment.
 

V1a2s2h4

Active member
Joined
Jun 10, 2014
Location
Rochester Ny
TDI
02 VW Golf
I pulled over and changed the vac gage to the connection in between the brake boater and n75 and cruising at 75mph it's pulling about 28" in vac coming off the vac pump. I'm assuming that's normal? I'll have to find the egr to check that next.
 

V1a2s2h4

Active member
Joined
Jun 10, 2014
Location
Rochester Ny
TDI
02 VW Golf
So I made the discovery kinda pushes me to belive that my vac system is fine. I replaced the n75, and ran new vaccum lines and on start up the car still only pulled 6" down to the turbo. I pinched the hose going down to the actuator and the vac gage climbed to 20". I disconnect the line going to the actuator and put my finger over the end of the open gage and it climbed to 20" again. On reconnecting the actuator line, it fell back down to 6". I started squeezing the line again and after several pumps, the system rose to a normal 17".

I'm kinda leaning towards the actuator being the culprit here. I'll have to look to see where on vcds can I see the actuator activity.

Fortunately enough, I have a replacement smart actuator since I needed one for the new turbo I was planning to drop in.

Ty for the tips so far guys, I'll keep you all posted
 

\/\/0J0

Veteran Member
Joined
Apr 27, 2010
Location
Knoxville, TN
TDI
Sadly, none anymore
Yep. If you can't build vacuum with the actuator connected but can with your finger over the same line, there's a hole in the diaphragm of the actuator

Sent from my mobile look-at device
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Yes, to simplify simply connect a vacuum pump and gauge to the actuator and pump it up to say 20 then watch to see if it holds or drops. If it drops, the actuator has a leak, likely rusted thru somewhere.
 

UhOh

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Dec 24, 2014
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PNW
TDI
2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
Location: Rochester Ny

Yeah, I'd wager on there being a rusted actuator:D
 

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
And if no splash shield then I'll double-up on my wager!

I'm so glad that I don't have to deal with rust like others do.
 

V1a2s2h4

Active member
Joined
Jun 10, 2014
Location
Rochester Ny
TDI
02 VW Golf
Hey now, she ain't too rusty under the hood, the lady I bought her from had her outfitted with a skid plate and the engine splash guards are still intact. The actuator visually is in good shape, a little dull cause of its age, but not visible rust on it.

Unfortunately my back up actuator is for a vnt and would require some fabrication/jerry rigging to get it on the stock turbo... I may as well wait for kermatdi to ship out my new one.
 
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