How to tell if turbos need replacing in as S4?

Post by **Druggie** » Mon Oct 04, 2004 1:53 pm

Appart from the tell tale noisy turbo bearings , how else can you tell if the turbos are faulty or need replacing?
What checks can the workshops perform to tell one way or the other?

Post by **Dippy** » Mon Oct 04, 2004 2:14 pm

That's a difficult question! Noise is the no. 1 indicator.

From what I've read often the turbos can actually increase performance as they are on their way out.
Also there may be oil leaks. Unlikely to be external, so check colour of exhaust smoke during start-up and how long it lasts afterwards. Also check for oil in the intake system (a little bit is OK), and of course if the oil level has been dropping over time.

I'm not sure what else can be checked without remover a turbo...

Post by **Golich** » Mon Oct 04, 2004 2:27 pm

My turbo failure first showed itself as a breif limp mode that resolved itself on restarting. The error codes DTC indicated odd readings from a lambda probe. This was thought to be the oil contaminating the probe. But there was no smoke.

Boost pressure and performance was fine for weeks after this incident. It was only on stripping (something?) I think it was the intake side of the turbo that oil was seen it wasn't using any noticeably oil otherwise the car appeared ok.

Therefore, in some cases its not that easy to determine. But his was only one type of failure i.e. a worn oil seal. See my gallery for pics of a failed oil seal on one turbo and good turbo for comparisson.

Post by **JonnyX** » Mon Oct 04, 2004 4:39 pm

Also, I would add that leaking oil has to come from somewhere so if you suddenly need to start topping up with
oil then something could be amiss. Also, you can find plenty of posts in audiworld - just search for dentists
drill

Dippy, could you define more what you mean by oil in the intake system? I have oil in my intake system but it
seems to be from the PCV valve (i.e. it's only in the near side tract)

Post by **Dippy** » Tue Oct 05, 2004 1:51 pm

Jonny,

Yes it is common to have a trace of oil there. That's what I meant by "a little bit is OK". As you know, if a turbo seal goes, quite a lot of oil can spill into the intake.

Post by **Druggie** » Mon Oct 11, 2004 12:43 pm

Guys the other day after half a day cleaning the car in me garage i started the car in rediness to go out i noticed a bit of oily smoke filling the garage as i had the door and sunroof open. i jumped out and looked at the exhaust and there was a faint bit of oily smoke coming out the exhaust but the garage was filling fast with greyish/white smoke. I stabbed the throttle which only made it worse. I swicthed off the engine and let it stand for hald an hour or so. When i came back it started fine with no oily smoke and hasnt since then but i dont know what to make of it. But the only issue i have is that the car seems laking in midrange torque when the turbos should be in full swing and giving me a right old shove in the back. Ive even struggled to keep up with a 04 325i auto.
Are my turbos on the way out? Or is this a typical maf failure?

Post by **Julesm** » Wed Oct 13, 2004 9:50 am

If you feel down on power then it sounds like it could be your MAF sensor or a loose / leaking hose.

Oily smoke may be an indictaion of oil passing the turbo seal, however this is more so if it smokes after the car has been running at idle for a few minutes as opposed to start up.

Post by **excursion** » Wed Oct 13, 2004 12:10 pm

Blue smoke points to the turbo's....

Post by **Verruckt** » Thu Oct 14, 2004 12:03 pm

excursion wrote:Blue smoke points to the turbo's....

Hey cool sig! (That's my car).

Post by **Druggie** » Mon Oct 18, 2004 1:18 pm

Good news turbos are ok and power loss was a loose hose. Now back to normal and no smoke whats so ever. Dealer thinks it was bleeding boost and running rich so maybe there was a build up of fuel and oil in the exhaust so when i started the car it all came out and being in a closed environment it accentuated the amount of smoke coming out of the exhaust.

Explanation of my sig -
Being a pharmacist i though it was cool as S4 in australia is shorthand for schedule 4 drugs which are prescripion only. Wasnt sure if anyone would get it though...

Post by **Dippy** » Mon Oct 18, 2004 1:22 pm

Tony,

With an air leak your turbos would have been working harder to maintain a given boost. So if you still have a warranty on that car, I suggest you still get something in writing that states you had an air leak. So if the turbos to die prematurely, you can reference it back to this original failure.

Post by **Imolavirus** » Fri Oct 22, 2004 12:18 am

you're not going to see an increase in performance as the turbos die in any case

Post by **Verruckt** » Fri Oct 22, 2004 5:59 am

Imolavirus wrote:you're not going to see an increase in performance as the turbos die in any case

N00b!

But yeah, he's right.

The day before mine went, my car felt very sluggish.

Post by **Druggie** » Sun Oct 24, 2004 9:01 am

Wll do just that and get the fault in writing
If i was to dyno the car what power at the wheels should i get to make sure the car is producing its full potential. (standard car)
Any other tests or things i should do to make sure the car is 100%?

Post by **Imolavirus** » Mon Oct 25, 2004 3:52 pm

i dont think you need to dyno the car. A simple boost log of requested vs actual will tell you a great deal about how your turbos are doing. Also, given that your MAF is still 100% good, a g/sec log will tell you how much those little K03's are pushing. Do you have a VAG-COM or some other logging capability?

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How to tell if turbos need replacing in as S4?

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