Boost Leak? (kinda long)

[D Piddy]

ok, so i'm not positive if i have a boost leak but i suspect i do. i was driving on the highway, rather spiritedly, doing about a buck 25. a felt a small loss of power, but all was ok, boost held. then when i let off, it was still ok, but when i got off the highway about 2 minutes later, and let of the gas for a short time, the boost didn't come back. it wouldn't go above 6-7 PSI. i'm chipped so it should be peaking aroudn 17-18. the ca felt very sluggish, most likely from the lack of boost, so i wasn't too worried, thought i prolly just need a new boost hose from my DV install last week. i was warned, oh well .

but i parked the car at the rink and when i came back out probably 2 hours later, and started it up, it was boosting to normal levels. however, this time, it sounds like the turbo's much louder. it could be just my imagination, but it sounds like the air can be heard easier.

could it be tthere's a hole in the boost hose? it would make sense since i could be hearin air escaping, but if that were so, wouldn't i experience a loss of boost? that lasted for two seperate car rides now so it seems like it's not changing. so, my question is, does this sound like a boost leak? and if so, is it possible that i have a boost leak where the only effect is a louder turbo noise and a fractonally slower spooling time?

[Daft]

It's a pain in the ass but, you should check all the boost hoses. That means:

BPV hoses
N75 hoses
FPR vacuum line
all hoses around the airbox

If all that fails, you should get a VAG-Com hooked up and check for a CEL. Perhaps you hit limp mode or a fouled sensor tripped a CEL.

[Mike~p]

this is totally off topic but turbo90awd....i love when i come across your posts...your sig is what keeps me searchin the forums

[xburbx]

^^^^^^^^^^^^^agreed^^^^^^^^^^

[nizmosx]

honestly i want to say that if you car is reaching full boost sometimes i dont think its a leak because if you had a leak i dont believe you would reach full boost. it could be possible however that you do have a small hole in a line but even then it would make sence that you would reach full boost one run then all of a sudden only pounds. do you have a old diverter valve in your car. maybe its time for a new one. i would however check all the vacum hoses mentioned a couple posts above as they are the cheapest fix if that is the problem. let us know what turns up.

[Daft]

Originally posted by Mike~p
this is totally off topic but turbo90awd....i love when i come across your posts...your sig is what keeps me searchin the forums

When I spotted the GIF file on the net, I knew I had to share it with the guys....

[D Piddy]

i just chnged my BPV last week, but i guess i need to check all the hoses. anyone wanna do a quick PS of an engine pic to show me which hoses to be lookin for? i'm kinda a newb to workin on the engine myself

[DDQ]

It sounds like you hit limp mode. Usually if you shut off the car for a bit, then restart, it will often go away.


Here's a crappy pic, but here's the basics to check for suspected leaks.

1. Hose from air filter.
2. N75 valve (has to small vac lines coming out of it).
3. BPV line. Runs up to the intake manifold. Also check the two larger diameter hoses connecting to the BPV.
4. FPR line.

NOTE: This is for my '97. Later models have the BPV in a lower spot, which would be in the lower left corner in the pic.

[pigliiit]

anyone know the size of those little fibery hoses, like the one that comes off the top of the bpv?

[DDQ]

Yes, they're 5/32" diameter, which is the same as 3.5mm.

[D Piddy]

ok, i'm gonna go check my FPR line bc that's where i had them tap for my boost gauge, maybe that connection got messed up. BPV hoses on BPV area are all ok, so i gotta go check some of the other ones posted. thanx a bunch. if anyone else has some suggestions, just keep 'em comin!! i'm just prayin it just went into Limp Mode and the louder noise is all in my imagination

[excursion]

I'd go with what Mike is saying, I was going to suggest limp. Sounds like you had a high spike :)

[D Piddy]

yeah, i just checked everything and everything seems not only good but in surprisingly good condition. it's prolly bc last year i threw a code and took it to audi and they replaced a bunch of vacuum luines os most of that shit mentioned is pretty new. the louder noise must be the Bailey's breaking in and gettin a little louder. guess i just havent't driven aroudn wiht my windows down for a couple days

[HotSauce]

Why don't you run the car, then rev it, and see if you can hear a hiss, from any of the hoses. Might as well shoot the horse again, just to make sure it's dead.

[OverSpun]

check your bypass valve again... it is possible for TT valves to be defective you know.. that could be the problem, if thats clear, put it back in and move on to the other hoses.

[DDQ]

Originally posted by OverSpun
check your bypass valve again... it is possible for TT valves to be defective you know.. that could be the problem, if thats clear, put it back in and move on to the other hoses.

Yeah, but there's no symptoms of a bad BPV here. He has full boost (after going into what sounded like limp mode). I think he just said he hears a hissing noise, which may or may not have been there before.

Most of the time a ripped BPV will cause boost "flutter" under load.

[OverSpun]

then is more than likely a cracked vacuum line. there are some places of the line that are hard to see, sometimes its just better to replace the lines and check, especially since vacuum lines are super cheap anyway. either that or something could be up with his software.

[D Piddy]

ok, so i still have a leak. the hiss is damn loud and it's just a little sluggish gettin goin and gettin the boost up. my guess is the vacuum line. i doubt i can do this myself so should i take it to my dealership? is this the kinda repair where they would have to test drive the car? bc if so they're gonna feel my chip. i should also disconnect the boost gauge too right? just in case so they don't see it my higher boost levels? and which is the vacuum line? is it the smallest hose comin off the BPV? oh and it's not a bad BPV, it's a bailey's, i'm still gettin boost and it's only a week old, so that's outta the question

[D Piddy]

sorry to keep this thread goin, but i've possibly narrowed down where the problema is. there appears to be an abnormal sound at idle coming from this region. is this the N75 valve or wutever?



this is where that close up is from



also, this is where my boost gauge was tapped into and the place that installed it seems to have done a good job. the hose is on pretty tight from friction and tight fitment, but the zip ties appear to be doing nothing, they can spin around the hose as if they're doin nothin. could this be a problem?







once again, thank you so much everybody. i know my questions get annoying but i don't have as much experience as many of the people on this forum and it just sux havin a car not workin right and not bein able to fix it. thanx again for all yur help on the matter. i think i'm just gonna take it to this VW/Audi/Bimmer shop near me to avoid the hassles of the dealer until i get a stock program for my ECU


EDIT: sorry for the blurry-ass pics. when my digicam is in digital zoom, it can't focus for shit. POC

[DDQ]

Personally, I would not have tapped that line for the boost gauge, but many have done it with no problems. I prefer the front line off the manifold. But, make sure there is no play in those hoses on that t-fitting where it was tapped. Can you easily pull those hoses off the fitting? If so, get some clamps and get it sealed up tight.

Those hard lines you pointed to in your pic do not appear to be the same as the FRP line you tapped, so if the sound is there, it should be unrelated to your boost gauge tap.

I'd inspect for visible cracks, and try to precisely locate the are the noise is coming from.

Based on your first post, it sounded like you hit limp mode, but afterwords everything was fine. If you're not experiencing loss of boost, and your gauge reads fine, then you may not even have a problem.

But,sometimes if you overboost (which threw you into limp mode), then the pressure may have pushed a hose loose.

Check the hose at connecting to the throttle body to make sure it's tight.

[D Piddy]

to clarify a couple points. i am experiencing other symptoms, slightly slower spooling and an audible leak. i hear the air escaping, even if i am hitting full boost. next, the third pic is unrelated to the first two. i just thought maybe the loose zip ties could be the cause. but the odd sound is coming from the region of the first two. wut's back there? and finally, where is the hose connection for the throttle body? i should prolly check that so long as it's relatively easily accessible

[ornjblud]

Check the "L" shaped hose that runs out of the intake manifold. That hose is a common problem. I had a similar problem to the one you describe. The "whoooshing" I heard was the air escaping from that hose.

You may have to feel around since you may not be able to SEE the tear.

[D Piddy]

Originally posted by ornjblud
Check the "L" shaped hose that runs out of the intake manifold. That hose is a common problem. I had a similar problem to the one you describe. The "whoooshing" I heard was the air escaping from that hose.

You may have to feel around since you may not be able to SEE the tear.

i'll go give it a look now, but my sounds more of a hissing than a woooosh. it just sounds like the turbo's a lot louder. not like when i let off, like a BOV, just whenever it's boosting it's as if i can hear the turbo a lot more easily. but i know it's just air escaping from some hose

[Daft]

There is a vacuum line for the EVAP system that runs behind the engine in the area in your picture. It does effect the vacuum system if it leaks so, you should definately trace it and look for tears.