Go Back   AudiWorld Forums > Audi Models > Audi A4 > A4 (B5 Platform) Discussion
Sign in using an external account
Register Forgot Password?


A4 (B5 Platform) Discussion Discussion forum for the B5 Audi A4 produced from 1995-2001 B5 FAQ

Welcome to AudiWorld Forums!
Welcome to AudiWorld.com.

You are currently viewing our forums as a guest, which gives you limited access to view most discussions and access our other features. By joining our community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join the AudiWorld Forums community today!


Reply
 
 
 
 
LinkBack Thread Tools Search this Thread Display Modes
Old 11-17-2009, 04:38 PM   #1
Audiworld Junior Member
Account #: 173357
 
Join Date: Nov 2009
Posts: 53
Send a message via AIM to reinstone79
Default Audi A4 Vacuum Hose Question

So I have a check engine light on, and it would appear the codes are basically telling me its a vacuum leak (and no, its not the gas cap).

So I found that on top of the intake manifold in the rear of the engine and on top of the throttle body there are several vacuum lines with different colors. There is a short blue and short brown cloth braided over rubber hose that go off to the driver side of the intake, and a black with tan spots hose and light green hose. All of the hoses are rubber with the braiding around them, but the green hose is hard plastic line after the rubber, and has a little rubber hose at the end of it after about 16" or so. This hose is just flopping around and isn't connected to anything!

Can anyone tell me where the green hose goes to in the circuit of vacuum hoses?

Should I just plug it off and see how the engine idles?
reinstone79 is offline   Reply With Quote
Old 11-17-2009, 06:00 PM   #2
AudiWorld Super User
Account #: 37725
 
AudiMick's Avatar
 
Join Date: May 2002
Location: Redmond WA
Posts: 5,102
Default You might want to provide year and engine type of your car.

There are significant differences.
__________________
2001 180 TTQ coupe (sold)
1976 Triumph Spitfire
2008 A4Q 2.0T (sold)
2003 A4Q 1.8T (sold)
1996 A4Q (sold)
AudiMick is offline   Reply With Quote
Old 11-17-2009, 07:06 PM   #3
Audiworld Junior Member
Account #: 173357
 
Join Date: Nov 2009
Posts: 53
Send a message via AIM to reinstone79
Default

Quote:
Originally Posted by AudiMick View Post
There are significant differences.
Oops... I meant to do that at the end. It is a 1996 Audi A4 Quattro 12V 2.8L V6. 116k miles... new timing chain, water pump, thermostat, pass side power steering rack and pinion, and various other updates.
reinstone79 is offline   Reply With Quote
Old 11-17-2009, 08:11 PM   #4
AudiWorld Super User
Account #: 37725
 
AudiMick's Avatar
 
Join Date: May 2002
Location: Redmond WA
Posts: 5,102
Default Here's the vacuum line diagram

Maybe you could identify which line is disconnected.

The "EGR mod" shown on the drawing was to prevent the EGR valve activating during normal driving. A few people did this to prevent a recurring problem on the 12 valve V6 "EGR insufficient flow".

The braided hoses should be replaced. They could be 13 years old. Silicon hoses work great.

About 8 feet of hose would take care of it. The only tricky one is the "bomb (vacuum reservoir)" underneath the ignition coils.

Another common place for a leak is around the iCV.
Attached Images
File Type: jpg 96_vacuum.jpg (38.0 KB, 550 views)
__________________
2001 180 TTQ coupe (sold)
1976 Triumph Spitfire
2008 A4Q 2.0T (sold)
2003 A4Q 1.8T (sold)
1996 A4Q (sold)
AudiMick is offline   Reply With Quote
Old 11-18-2009, 03:54 AM   #5
Audiworld Junior Member
Account #: 173357
 
Join Date: Nov 2009
Posts: 53
Send a message via AIM to reinstone79
Default

Quote:
Originally Posted by AudiMick View Post
Maybe you could identify which line is disconnected.

The "EGR mod" shown on the drawing was to prevent the EGR valve activating during normal driving. A few people did this to prevent a recurring problem on the 12 valve V6 "EGR insufficient flow".

The braided hoses should be replaced. They could be 13 years old. Silicon hoses work great.

About 8 feet of hose would take care of it. The only tricky one is the "bomb (vacuum reservoir)" underneath the ignition coils.

Another common place for a leak is around the iCV.

This diagram works great! Thank you very much! I'm not in front of the car to know for sure at the moment, but I believe the line I'm talking about is in fact the one going to the vacuum resevoir. I remember the green lines were part of the "Y" connection, and it is probably the longest hose there. So the question is, how in the world do I get to that vacuum resevoir?

It also makes sense that the line that is disconnected is to the vacuum resevoir because I felt some differences in the brake pedal travel at idle and I just did some brake work with a new ABS pump and pads and bleeding.

So is reconnecting or re-running this line going to be a disaster? Would just rubber vacuum hoses work as replacements?

This help is much appreciated.
reinstone79 is offline   Reply With Quote
Old 11-18-2009, 05:10 AM   #6
AudiWorld Super User
Account #: 37725
 
AudiMick's Avatar
 
Join Date: May 2002
Location: Redmond WA
Posts: 5,102
Default If the bomb is still good (not leaking) you should be OK .

It's awkward not impossible, regular rubber hose is fine if you can find the right ID hose. BMW dealers sell the braided hose by the foot, but it's $$.
__________________
2001 180 TTQ coupe (sold)
1976 Triumph Spitfire
2008 A4Q 2.0T (sold)
2003 A4Q 1.8T (sold)
1996 A4Q (sold)
AudiMick is offline   Reply With Quote
Old 11-18-2009, 12:14 PM   #7
AudiWorld Senior Member
Account #: 150900
 
Join Date: Jun 2008
Location: Yorba Linda CA
Posts: 1,516
Default

Could you explain the EGR fix? My '96 would always set the "flow insufficient" code until I cleaned the clogged EGR and manifold passage. My understanding is that the temp sensor at the end of the passage has to get hot when the EGR valve is open, otherwise the fault code.
turbo510 is offline   Reply With Quote
Old 11-18-2009, 04:57 PM   #8
Audiworld Junior Member
Account #: 173357
 
Join Date: Nov 2009
Posts: 53
Send a message via AIM to reinstone79
Default Where is the "bomb" vacuum reservoir?

Quote:
Originally Posted by AudiMick View Post
It's awkward not impossible, regular rubber hose is fine if you can find the right ID hose. BMW dealers sell the braided hose by the foot, but it's $$.

So where is this stupid vacuum resevoir? Under the ignition coil? I have been looking around, but not sure where it is. Is it that canister that looks like a bloated insect with three ballooned out circles?

I'm Audi-ignorant, but mechanically inclined in fixing many other cars. So this is just getting interesting to me.
reinstone79 is offline   Reply With Quote
Old 11-18-2009, 05:11 PM   #9
AudiWorld Super User
Account #: 37725
 
AudiMick's Avatar
 
Join Date: May 2002
Location: Redmond WA
Posts: 5,102
Default

Quote:
Originally Posted by turbo510 View Post
Could you explain the EGR fix? My '96 would always set the "flow insufficient" code until I cleaned the clogged EGR and manifold passage. My understanding is that the temp sensor at the end of the passage has to get hot when the EGR valve is open, otherwise the fault code.
The EGR valve is controlled by a solenoid to give two modes of operation:

When the solenoid is off vacuum from the plenum opens the valve. So when intake vacuum reaches a certain level at around 3500 rpm the EGR valve opens and dumps exhaust into the intake for emission purposes.This happens all the time when driving.

The ECU can also turn on the solenoid and provide vacuum to open the valve. The ECU randomly tests the system for operation to make sure the emissions system is working. This is just a test and is not all the time.If this test fails it sets the CEL.

Unfortunately as the cars get older, blow by gas condense and block up the EGR port, which then needs to be cleaned.

The EGR mod allows the valve to open when the ECU tests the emissions but not allow the plenum vacuum to open it.

Thus the valve is open less often, this means potentially more power and that the EGR passage will block up less often.

However the EGR passage must still be unblocked for it to work.
__________________
2001 180 TTQ coupe (sold)
1976 Triumph Spitfire
2008 A4Q 2.0T (sold)
2003 A4Q 1.8T (sold)
1996 A4Q (sold)
AudiMick is offline   Reply With Quote
Old 11-22-2009, 04:50 PM   #10
AudiWorld Member
Account #: 42821
 
Bruch's Avatar
 
Join Date: Sep 2002
Location: Irwin, PA
Posts: 301
Default Interesting indeed

Quote:
Originally Posted by reinstone79 View Post
So where is this stupid vacuum resevoir? Under the ignition coil? I have been looking around, but not sure where it is. Is it that canister that looks like a bloated insect with three ballooned out circles?

I'm Audi-ignorant, but mechanically inclined in fixing many other cars. So this is just getting interesting to me.
The reservoir is right next to the coils, its a black plastic ball, the size of a grapefruit.

AudiMick, thanks so much for the diagram, and the EGR fix reminder. I was straining my eyes in the Bentley this morning trying to get the lines squared away on a A4 I just bought. There was no vacuum supplied at all to either the EGR, manifold change-over , or FPR. But the car was running OK, for 3 weeks, until this past friday when it became hard to start. Way too rich/flooding. still working this out.

Bruch
Bruch is offline   Reply With Quote
Old 11-22-2009, 04:50 PM
AudiWorld
Audi R8




Paid Advertisement
 
 
 
Reply

Tags
2004, a4, audi, b5, b6, check, diagram, engine, hose, hoses, intake, light, line, reservoir, rubber, vacum, vacuum


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -8. The time now is 04:39 PM.


Copyright 2014 AudiWorld.com Audi Enthusiast Community