So my car just began to stumble at times at lower RPMs and cut out (from overboost) at mid- higher RPMs. I guess the stumbling problem is a vaccuum leak, but that started happening after the overboost problem.
I looked on the SJM site and it said to check the following, I've also searched the forum, but people list these things and not much is said on how to actually check for the following...

Check Lower Waste Gate Hose from Intake Manifold for leaks/restrictions
Check Vacuum/Boost Hose from Intake Manifold to Engine Control Unit (ECU) for leaks
Check Waste Gate Diaphragm for Leaks
Check Waste Gate Valve for sticking or restricted movement
Check Waste Gate and Waste Gate Solenoid Hose connections for incorrect routing
Check operation of the Waste Gate Solenoid

so now for my questions if you guys dont mind ;)

1. How do you check for leaks and restrictions? I heard there is a way to pressure test, but have no clue how to do so. Someone said i should remove all of the intake hoses and bend them to expose cracks, is that the easiest way?

2. Where is the WG diaphram, and how do I check that for leaks?

3. How do you physically check the WG valve for sticky movement?

4. How do you check the WG solonoid?

I guess thats about it, the rest I understand how to check.. And I thought the NA cars were a PITA
hehehe
Thanks in advance!

1. Checking for leaks and restrictions.
Leaks is best done by using a can or something about the size of the intake hosing after the turbo but before the throttlebody. Fit a compressor fitting on the can and set your compressor to 10 psi or so to mimic high boost. Hook it up to your intake hosing and you'll see/hear a leak. I used a Pint paint can which fit my Throttlebody hose. For stock turbo plumbing maybe a soup can is good. (seriously) PVC pipe is excellent too.

Visually flexing the hoses and looking/feeling for hardness and cracks is a good technique.

a. Check Lower Waste Gate Hose from Intake Manifold for leaks/restrictions. Wastegate
<img src="http://images.google.com/images?q=tbn:VDa38SCCVGgJ:ffp-motorsport.com/tuning/tunpics/hukkis.jpg">
See the rubber ring between the top and bottom. That is the diaphragm. The bottom is boost operated to pop open the spring and vent exhaust pressure. There is a hose connecting the bottom to the manifold. You can see the banjo bolt in the picture going to the bottom. The top cover has a nipple which isn't used except on some 10V cars.

b."Check Vacuum/Boost Hose from Intake Manifold to Engine Control Unit (ECU) for leaks"
That is a hose that goes to the ECU in the footwell on the passenger side where the ECU is. Typically that hose starts at the back of the intake manifold and runs along the firewall to the T splitter where is branches to various things. There are several vacuum lines taken off the intake manifold for vacuum reservoiur, vacuum operating switches and differentials. Usually a cluster of 3 hoses with Banjo bolts or standard barb fittings on the intake manifold AFTER the throttlebody.

"Check Waste Gate Diaphragm for Leaks"
See the picture above. Its the rubber bladder inside that. Don't overtorque the little nuts when you retighten the wastegate cover.

"Check Waste Gate Valve for sticking or restricted movement" You can take it off and manually operate it or, disconnect the vacuum line that goes to the bottom of the wastegate and feed it some compressor air (maybe 15psi). You should be able to hear it open up. Just a clunk is all you'll hear. You could also apply vacuum to the nipple on the top of the cover. That'll do the same thing.

"Check Waste Gate and Waste Gate Solenoid Hose connections for incorrect routing" The Solenoid is the electric plunger which controls the air operation of the wastegate. It helps keep the WG shut when you're not at boost yet. If is been replumbed all funny, strange things happen. NOt likely the culprit unless the solenoid is bad. The solenoid is a simple electric on/off switch with one input and two outputs. So 3 vacuum lines go to it and two wires. commonly called WGFV (wastegate frequency valve)

"Check operation of the Waste Gate Solenoid"
Gotta determine the voltage and make sure the plunger is moving. I'm not sure of the voltage of the solenoid on your car. Some clever work with 1.5V batteries or a 9V will do the trick. Again, one input and two output hoses. When the plunger moves after it gets electic power it just switches the air flow to the other outlet. Simple (a vacuum version of an electric relay)

You'd be out of your mind.

The simplist way I know of is definately a pressure tester.

****I will post pics of mine in a couple minutes****

You can build it yourself for just about nothing, using stuff from home depot. Basically youre mimicing a turbocharger, with the car off, so you can listen for leaks. Take the hose that's connected to the turbo outlet off. (the one going to the IC) Insert the pressure tester in there, connect it to an air source, and listen.

This will show you any boost leaks you have. However, the overboost situation is another thing. Every overboost situation I've ever had has involved the wastegate... I'd check that one more time. I believe a lack of fuel will also recreate this situation.

Leaks mean no fuel when its CIS.
There is always vacuum between the CIS airplate and the turbo. Thats is what pulls up the airplate.

There is less vacuum between the CIS airplate and the turbo on idle. So if you have a small leak there.. Its run lean on idle and bog/stall. Under boost the leak is overcome because the vacuum is greater in front of the turbo and the airplate moves. Still lean, but working.

Check in front of the turbo between the CIS metering box and turbo. All hoses going to that as well.

<img src="http://pictureposter.audiworld.com/49550/000_0072.jpg">

FYI, the widest part fits snugly inside that Rubber hose comming from the turbo... It looks strangely small in the pic.

Best of Luck

Really a great write up! As soon as I make the pressure checker, I'll start solving the problem.
BTW, I saw Bruno yesterday when I went to buy some Pentosin. They relocated the shop a couple miles away to a better area and closer to my fathers shop. I never go there with out seeing a UrQ or something really interesting.
Well thanks again for the help!

Nice contraption, and I'll be doing almost the same... I already made a simple dyi pressure bleeder for the brakes ;)

I wanted to bring you up and that I sat in the car ect, but they were crazy busy... Next time!

Mine is really mcGyver. We took a small paint can. drilled a hole in the end and then threaded in a compressor fitting with plumber's dope. Took 3 minutes.

is a rotted lower wastegate hose or torn WG diapraghm...

Lower WG hose is eay to check. Simply remove and inspect.

WG can be checked with a mighty vac applied to the upper WG chamber. If it holds vacum it's good.

Let us know what you find out.

Steve
Michigan

All this info should be archived on the AW site.

I Wiki'ed it onto the Audifans.com list, in the "KnowledgeBase" and gave credit.<ul><li><a href="http://www.audifans.com/twiki/bin/view/Audi/BoostLeaksVacuumLINES">Cut and Paste of this Searchable in the Audifans.com site</a></li></ul>

Check the MM hose and the lower IC hose. I've popped several MMs. Sometimes, if the hole is small enough it just acts like a BOV. If it is too big it may be causing a leak that will cause hard starting and lopey idle.

I have a 1987 5000 CS Turbo Quattro. Car used to run fine, boost 1.1 or so if I recall. Anyway, it will only get to about .8 now and "shudders" at that point. Engine stumbles and won't put out more than .8. Is this the same thing as andre? Or is it something more? I hope it's not too serious as I just put in a new hydraulic pump, bomb, brake master cylinder, power steering rack, and tie rod ends. I'm running out of money!!! Help!