# Turbo noise....possible failing turbo



## Uberhare (Jul 30, 2003)

I'm getting an intermittant "dentist drill" like sound coming from the passenger side turbo (I think). It doesn't make the sound all the time. Some days it's there and some days it's not. The sound is definently related to the throttle position and boost level. Car has just under 40,000 miles and the engine is bone stock. The car did not have service records, but it appears to be maintained well. I have no idea how often the oil was changed or what kind was used. I've had the car for several months and use only Mobil 1 0W-40 synthetic. I changed the oil just after purchasing the car and looked carefully at the used oil. It appeared a little dirty, but no metallic flakes or unusual color/smell. Car seems to run good without any boost problems that I can tell. The noise just has me concerned. Would a boost leak somewhere maybe cause the noise?


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## sims159915 (Jan 24, 2005)

does it sound like that on start up? my buddies car is having that problem during hgih idle on start up


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## GLS-S4 (Jun 6, 2005)

*Re: Turbo noise....possible failing turbo (Uberhare)*

Does it make noise only when cold and subsides when warmed up?
It is possible for a boost leak to cause turbo spool whistle.
If you haven't already, check the BPV's as they are #1 suspect if stock and it never hurts to retest if not stock.
Perform an intake pressure test for $20 of parts:
http://www.awe-tuning.com/medi...r.pdf
I don't go over 10psi while pressure testing intake and I try to keep the intake pressurized for as short time period as possible.


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## Uberhare (Jul 30, 2003)

*Re: Turbo noise....possible failing turbo (GLS-S4)*

The noise ONLY occurs during driving and under acceleration. I never hear it during idle, warm up, or while cruising. I guess it does sound more like a whistle than a drill. So, you think a boost leak close to the compressor would cause a whistle sound under acceleration (boost)? It makes sense.


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## GLS-S4 (Jun 6, 2005)

*Re: Turbo noise....possible failing turbo (Uberhare)*

It does not have to be close to the compressor, an intake leak anywhere in the intake system is a problem.
Another thought is to VAG-COM log Engine - Block 115 under WOT, typically 3rd gear to get a good run of engine rev up. Use Excel to see 1st column RPM's along with 3rd column Boost Requested vs 4th column Boost Actual. Boost columns should not differ by more than 20mbar, else you likely have a boost leak or other major problem. Also note your local atmospheric air pressure at test time and subtract it from the numbers you see in columns to get actual boost values.


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## Uberhare (Jul 30, 2003)

*Re: Turbo noise....possible failing turbo (GLS-S4)*

Excellent info. I'm looking to purchase the Ross-tech VAG kit this week. I'll build the pressure tester tonight.


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## Uberhare (Jul 30, 2003)

How difficult is it to replace all of the stock rubber boost hoses? Is this something that be done without disassembling half the front end? I might just invest in the upgraded Samco hose kit and TB boot.


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## GLS-S4 (Jun 6, 2005)

*Re: (Uberhare)*

Are you considering upgraded turbo's with chip? Stock hoses are fine even if chipped while using stock turbo's, except for the common stock TBB issues.
It would be difficult to get access to some hoses and connections while car is intact.


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## Uberhare (Jul 30, 2003)

*Re: (GLS-S4)*

That's what I need to know. Thanks. Looks like I'll replace the TTB and DV's before I chip it. I will eventually upgrade to K04's when the stock turbos give up.


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## Uberhare (Jul 30, 2003)

After a little more research I'm being to suspect it's a maybe the tensioner pulley or some other rotating part. Or maybe the water pump.


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## GLS-S4 (Jun 6, 2005)

*Re: (Uberhare)*

How did the intake pressure test go?
VAG'd boost?
Another thought... Do you have a leaking valve cover gasket? Typically a small oil leak will accompany. It can create a small boost leak and may be audible only under boost.


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## Uberhare (Jul 30, 2003)

*Re: (GLS-S4)*

Pressure test will happen this weekend. Don't have VAG, so I can't perform that test. Car is going into the dealer on Monday to repair leaking valve covers and/or cam seals, hopefully under extended warranty. I'm going to have them check over the hoses and turbos to make sure everything is OK.


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## GLS-S4 (Jun 6, 2005)

*Re: (Uberhare)*

My sole local dealer would charge you to "check over the hoses and turbos to make sure everything is OK" by test driving the piss out of it








You could wait til car comes back from dealer valve cover repair to see if noise is gone. If noise still present after valve cover fix, then proceed with your own intake pressure test and VAG boost logging checks http://****************.com/smile/emthup.gif


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