Boost Leak Test/Question - N80 Purge Valve

[audis4az4ever]

I have tried searching on the forums but I could not find an answer my specific question.

I have a 2000 Audi S4 with GIAC chip, new 710N diverter valves and have been performing a boost leak test on my car thanks to all the great information I found on this forum the past year. I have fixed all the boost leaks that I can find. I am using an air compressor and a boost leak tester with the gauge that I purchased from turboboostleaktesters.com

So the issue I am having is that when I do a boost leak check it is maxing out at about 13-14psi. I can't find any other boost leaks. The strange thing is when it hits about this range I can hear (and feel) the N80 purge valve turn on and it sounds like it is bypassing air thru it. I tried it with the electrical connection to it plugged in and unplugged. Is this normal? Could the N80 purge valve be going bad or is this a symptom of another problem? Any help would be very appreciated. Thank you!

[axnjaksn]

any chance you have video of the leak, noise, whatever it is your referring too

[audis4az4ever]

I don't but I will try this week.

[airjawed]

Why is the N80 on? Are you doing this with ignition on? Car should be off.

Is the 710 in the right way? Lots of people put it in the wrong way.

[zillarob]

They way the check valves are setup for that system, it should never see psi from a test in the first place.
Check the green check valves near it, and the one near the n249 or on the rear driver corner of the motor.

[audis4az4ever]

The ignition is off. The 710Ns are in the normal way with the vacuum hoses facing each other, not in the reverse order when them pointing up.

[audis4az4ever]

I was thinking possibly the same thing with the green check valves. I ordered two of them already and should be getting them tomorrow or Friday. Is there a good way to test the two green check valves?

[zillarob]

If you have the later style (no fhose) you can pull the line off the tbody.
If you can blow, the one by the #1 inj is bad.
If you can suck, the one top center of the mani is bad or the n80 is open.

Same if you have the fhose, just a little tougher.

[Zba]

If you have the later style (no fhose) you can pull the line off the tbody.
If you can blow, the one by the #1 inj is bad.
If you can suck, the one top center of the mani is bad or the n80 is open.

Same if you have the fhose, just a little tougher.

So you're pretty familiar with sucking and blowing eh? xD

[audis4az4ever]

Thank you for all the good information. I do have the f-hose. I already ordered two green check valves so after I replace those I will test the old ones off the car to see if one or both of them were bad.

As for the N249 check valve I took a picture of how the vacuum hose routing looks on my car. I don't know if it is clear enough but thought I would double-check with you all to make sure it looks correct. The arrow on this check valve is pointing to the rear of the car.

Just to make sure I understand the concept of the check valve and its operation during a boot leak test. When pressurizing the system the pressure should be going against the direction of the arrow and should be causing the check valves to close?

Thank you so much everyone for all your help!

http://s285.photobucket.com/user/kjp...00%20Audi%20S4

Edit: Sorry forgot to send the link to the pictures

[zillarob]

So you're pretty familiar with sucking and blowing eh? xD

I try not to, leaves a bad taste in my mouth


The arrow is the direction it can flow. Not always, but the arrow usually points to the line that goes to the intake.
The one on the top center will point to the hose to the fuel rail and to the inlets.

[zillarob]

Hard to tell from the pic.
The leg with the check valve goes to the intake Mani.
The other 2, 1 goes to the n249 and the other to the vac can in the dside fender.

[audis4az4ever]

Hard to tell from the pic.
The leg with the check valve goes to the intake Mani.
The other 2, 1 goes to the n249 and the other to the vac can in the dside fender.

Sorry about the bad picture. So the leg with the check valve goes to a T. From the T it goes to the intake manifold like you said and the other line on the T goes to the N249 (side closest to the rear of the car).
The other 2, 1 goes to the N249 (side closest to the front of the car) and the other to the vac can in the fender like you said.

Thanks again!

[zillarob]

Sounds right.

[audis4az4ever]

Just to give you all an update. I removed the two green check valves and sure enough one was leaking. I received the two new ones in the mail and installed them. I did a boost leak test again and now it is holding between 18-19psi using my small 2 gal 100 psi compressor. Not sure if I should be able to get more than that but that is much better than the 13-14psi that I was getting before.

For the check valve near the N249, do you think I should check that too? Or does 18-19psi with my air compressor sounds about right? Thank you so much everyone for you help! I learned a lot from you all!

[zillarob]

Which one was bad? The one by the inj would cause boost issues, the one up top might make it idle funny.
Might as well check the other one while you are there. Just pop the easiest hose to get to off after the valve and see if it blows air.

You should be able to hold enough psi to blow the tester or other hoses off, but Ive never used one like that and hard to say on the psi without seeing the setup.
If its holding 18-19 and all you are hearing is the oil bubbling, Id say you are prob good.
Drive it and see if it throws any codes?

[audis4az4ever]

Which one was bad? The one by the inj would cause boost issues, the one up top might make it idle funny.
Might as well check the other one while you are there. Just pop the easiest hose to get to off after the valve and see if it blows air.

You should be able to hold enough psi to blow the tester or other hoses off, but Ive never used one like that and hard to say on the psi without seeing the setup.
If its holding 18-19 and all you are hearing is the oil bubbling, Id say you are prob good.
Drive it and see if it throws any codes?

The green check valve closest to the injectors on the passenger side was bad. Probably was causing my boost issues like you said. The green check valve on top of the IM was good but I replaced it as well just as preventative maintenance.

You are right about the pressure testing. I hear oil bubbling from the oil cap area (I did take the oil cap off ) and it holds 18-19psi. I will test drive it this afternoon.

Thanks again!!!

[audis4az4ever]

After replacing the two green check valves, the difference is amazing! Car runs so much better with no hesitation like before on WOT. Thanks again everyone!

[RocksForsSale]

Where's the best place to get these check valves? I think I have the same issue.

[audis4az4ever]

I cant remember for sure where I bought them. I think either ecstuning or genuineaudiparts.com
Part #078905291A or 078905291B. The B part is the newer revision. Hope that helps. I suggest replacing all of them for peace of mind

[Grip99]

Bringing this thread back to life.

My 2000 threw some codes

P1557 (Charge Pressure Control - Pos Dev)
P1137 (Bank 2 (add) System too rich).

The car has a rough idle, and my boost gauge would sometimes drop to -15 vac from the normal -18/-19 vac. I feel the car lost some boost pressure as well. The car holds 13 psi under full load. The car is chipped with apr stg 2.

I performed a boost leak test at 15 psi, and i noticed that my N249 check valve was leaking out of the check valve seams after i sprayed some soapy water on it. I sprayed the green check valves as well and they seem to be fine. But i will check them the way it was stated earlier in the thread. Would that leak cause the codes i listed above? Im obviously going to replace it, but i cannot find the check valve with 3 ports like the image above in the thread.

Just to mention, i have an apr Bi-pipe, and my DVs are working fine. I have not gone after the N75 yet.

Any help would be great! Thanks guys

[IMG][/IMG]

[jaychen]

Bringing this thread back to life.

My 2000 threw some codes

P1557(Charge Pressure Control - Pos Dev)
P1137 (Bank 2 (add) System too rich).

bad n75 can cause the first code, just so you know.
the second code can come from a few different things. bad maf, bad fpr, faulty evap system.
have you checked fuel trims (032)?

[christianb5s4]

Are both green check valves the same part? Specifically this one:

https://www.europaparts.com/in-line-...78905291b.html

[Grip99]

bad n75 can cause the first code, just so you know.
the second code can come from a few different things. bad maf, bad fpr, faulty evap system.
have you checked fuel trims (032)?

Thanks for the response.

I ordered the new n249 check valve and will be throwing that in on sat. Just to let you know, my evap system is "coded out" based on what the previous owner says, but when i run the readiness it says its ok. My rear o2s are coded out as well.

Ok good to know about the n75. I havent looked into that yet. - As for the fuel trims, i have looked at them along with (033). The long term fuel trims were sitting at -3.1% and -4.9% (in order from first block) and the short term fuel trim (033) were fluctuating between + and - 2% on each at idle. My primary o2s are new.

[wbrunner23]

Are both green check valves the same part? Specifically this one:

https://www.europaparts.com/in-line-...78905291b.html

Yup, I got both from Europa as well. Was the best price I found, but GAP sells them for $26.18. Shipping costs may be the determining factor, but shipping to you from GAP will likely be quicker than Europa since Europa is located in NJ.

[Grip99]

Are both green check valves the same part? Specifically this one:

https://www.europaparts.com/in-line-...78905291b.html

I am pretty sure they are the same.

[christianb5s4]

Yup, I got both from Europa as well. Was the best price I found, but GAP sells them for $26.18. Shipping costs may be the determining factor, but shipping to you from GAP will likely be quicker than Europa since Europa is located in NJ.

I am pretty sure they are the same.

Thanks guys, I just ordered two. Seems like a good thing to replace just in case.