No ideas left. Turbo replaced and everything checked still not boosting.

[dmg312]

So a long story short. My second turbo blew at 52K miles. 2,000 miles over my warranty, and 3,000 over the turbo replacement warranty from the last one going.

I have replaced the turbo with a new one. replaced a broken cracnkcase hose, and I'm still not getting all the boost requested. I've checked all the pipes, intercoolers(dual), and everything in between. The shop is saying the only thing they can think of is a bad wastegate.

Has anyone ever heard of a bad wastegate on a new turbo? I can't name all the tests that have been done on the car, smoke and mist tests to find boost leaks, but what else can be done to find what's wrong?

I consider myself pretty knowledgable aboout this stuff, but I am not near my car where it is being fixed. Happened far from home, so it's a very reputable VW Audi shop on the other side of town. going to see it later today anything Ishould look for?

Thanks for the help.

[IronAudi]

Have you checked the DV?

[dmg312]

Checked the DV, N75, Hoses, intercooler, gaskets, everything I can think of.

[lookaught]

you can test the wastegate itself you know. You just need to attach a hose and a finely adjusted air compressor delivering whatever boost you want and see if it opens. Probably easier to take it off the car to do this. This is commonly done to snych turbos for bi-turbo setups.

[1.8G]

had the same experience... turned out that the cat was bad, and was restricting exhaust flow so i could only produce ~3 psi... do you have any odd rattles at idle?

[CyberPMG]

^^maybe an exhaust leak or cracked exhaust manifold? you may not have enough backpressure to get the required boost.

[Splattj]

You should do a boost leak test:
http://forums.audiworld.com/a4/msgs/1659806.phtml

[PRY4SNO]

You should do a boost leak test:
http://forums.audiworld.com/a4/msgs/1659806.phtml

Did you actually read the OP?

I can't name all the tests that have been done on the car, smoke and mist tests to find boost leaks, but what else can be done to find what's wrong?

That's a brutal situation, GL!

[Papachristou]

i had a similar problem (i leak tested, couldnt find anything).. turned out it was a faulty APR R1 DV... do you think one of the plastic end caps on the intercooler could be cracked and only opening up under boost? i know u said u checked them, but...

[Splattj]

Did you actually read the OP?

I did. Smoke and mist tests while the car is running can't cover all of the system and a visual inspection of all the pipes doesn't rule out a boost leak.

If, when pressurized, there's no indication of a boost leak, the only two components left are the wastegate and bypass valve. I've had four turbocharged cars and I've been through everything. Cracked flapper valves on the internal wastegate flapper, clogged cat (which ended up failing spectacularly!), leaky BOV, broken endtank, you name it. For $15 worth of home depot parts, it's worth pressurizing the system.

[alexza4]

Did the problems begin right after you went Revo?
Not sure if it'll help, but i just couldn not get the proper boost after going K04 (GIAC, stg2+), checked everything 10 times over, tunning shop kept saying bad N75, or wastegate, tested wastegate - no problems replaced N75 - still same. So finaly i ended up getting rid of (brand new) N75 altogether and going turbosmart MBC - that did it. Its been perfect boost ever since.

[Killerteve]

I doubt it's a manifold issue cuz I have recently had a leak between manifold/turbo. The car sounded like a Harley but the car was still able to reach full boost with Revo stg 2 (26 psi). If you checked all the hardware/mechanical parts I would look to the software or maybe it's still an N75 issue like alexa4 said.

[dmg312]

I'm starting to think it's more likely a bad wastegate. How do you check that?

Obviously I'm paying to have the turbo removed again, but I want to check that befor eI do anythting else.

[ILoveT]

Take out your primary O2 and if you boost significantly more or at all then your cat is bad.

[LampyB]

if it comes down to it, call up a solid local audi shop and usually they will cover the cost of a tow if you want them to finish the work. i almost had this done with a clutch job, but in the end it was such a large repair i didn't want to transport my transmission while outside of my car...

good luck

[Splattj]

Wastegate failures usually manifest themselves by overboosting. If the diaphragm fails, it won't actuate and the turbo will make maximum boost. If the actuator arm becomes disconnected from the flapper valve, or if the flapper doesn't seat properly, you will lose boost. In your case, since you're not getting enough boost and you have a new turbo, you most likely have a case of excessive backpressure, a bad boost control selenoid (N75), a boost leak, or a software issue.

How much boost are you getting vs. expecting?

[dmg312]

The issue is this. (taken from the tech account as I have yet to drive it. Went to yesterday but got stuck in 45 minutes of traffic before I even left my side of town.) Whne the accelerator is hit, boost comes on, when the car requests a spike the turbo kind of builds a little, flutters, and drops down some and holds steady. I'm not sure of the numbers, but instead of producing 1+ power it is more like stock.

To me it sounds like thte wastegate is bad, and cannot hold boost. As boost builds, and there is a spike either a bad seal, or bad spring lets it open and excess boost tis just passed by.

I was told the N75 was checked. How much is it tot rplace that, and how easy. Might be a good step before I take the plunge and have the old wastegate put on the new turbo.

[CyberPMG]

A new N75 is $100 at ECS. I have a new one I don't need that I can let you have for much less. PM me if interested.

It's not too difficult to replace, but you need to work in a slightly tight area to get everything connected. Take your time, and you can have it swapped out in under an hour.