No boost, possible failure of turbos.

[BaSen]

Hi, i was just asking for advice here since i bet you guys know more about this than me.

At the moment, my S4 runs like <beep>. I've got 0 boost, and there's also BIG BIG BIG whining, even on very low revs -1500rpm on every gear which sounds like a leak of big proportions.
It happened when i was driving my car (as any S4 owner would) on 3rd gear, full throttle, at around 6k rpm it suddenly stopped accelerating with this whining sound as followed.

With that said i've investigated what could be wrong. No leaks found anywere.
Anyone got any tips on what could be wrong

And my last question that follows is: Are my turbos completely wrecked?

I'd appreciate any answer good or bad.

[confusionhunter]

OPTIMISTIC ANSWER: there is a possibility that a boost hose has come off. Like at the top of one of the intercoolers which you wont see with out pulling bits off. the noise may be simply that you can hear the turbos as the intake system normally does a good job of muting them....
Hopefully, if you do a pressure test it will find the leak, and it sound like a major leak. Its unlikely that BOTH turbos have gone pop, even with one totally goobered you would expect at least some boost from one....

Pesimistic answer: Yes, your turbos are completely wrecked, it will cost loads to rip the engine out and chenge em but at least you can get KO4 ( do a search loads of material on this subject.....

Either way your next step is diagnostic pressure test. Do you have a boost guage? so you actually know you have no boost?

[BaSen]

Yes i have a boost gauge and i've got vacuum in the system.
And as soon as i give throttle it goes to 0 boost and loads of whining.

[s4yogi]

Sounds strange to be no boost at all unless both turbos are kaput have you checked the TBB throttle body boot

[confusionhunter]

Good, then the chances are its a major boost leak, as said it could be the throttle body boot which are very common for going. but if its noisy i suspect somewhere nearere the turbos, if its not a leak then potentially it could be the turbos....

[BaSen]

I've upgraded to a Samco silicone TBB. So that shouldnt be the problem tbh
The strange thing is that i've had the car up in the air once, didnt remove anything though but just felt where the hoses could've gone loose, didnt find any of the IC hoses loose nor any big holes in any of the mentioned..

[derdle]

Have you any fault codes from vag-com? Boost pressure leaks will normally cause the car to go into limp home mode which will give crap performance.

Since you're in Sweden the stock answer of "take it to MRC" would be costly...but probably worthwhile!

Paul

[DavidT]

Boost leaks don't really cause the car to go into limp mode do they ? thats why the turbo(s) get damaged because they overspin.

Sounds bad, but I reckon it needs a pressure test to fix any boost leak(s) and then see if it makes good boost and both turbos are quiet. Sometimes the boost leak sounds like the dreaded damaged turbo whine.

Good luck and please update us with progress.

[UKS4APR1]

Yes i have a boost gauge and i've got vacuum in the system.
And as soon as i give throttle it goes to 0 boost and loads of whining.

Remember 0 boost on gauge is actually SOME boost as otherwise it would be a negative reading (vacuum).

[derdle]

Boost leaks don't really cause the car to go into limp mode do they

Mine did iirc!

[confusionhunter]

Remember 0 boost on gauge is actually SOME boost as otherwise it would be a negative reading (vacuum).

Nah mate, thats still no boost, you get a reading of 0 in NA cars when they at Wide open throttle.... means its at atmospheric pressure.

[dazzer]

Boost leaks don't really cause the car to go into limp mode do they

Mine did iirc!

Mine 2

[UKS4APR1]

Nah mate, thats still no boost, you get a reading of 0 in NA cars when they at Wide open throttle.... means its at atmospheric pressure.

N/A engine would not be running at 0 ! how would the air be getting to the cylinders? It takes Boost to get to 0. You either suck it in (vacuum) or force it in (boost) it can't just go in on it's own.

[confusionhunter]

OK we'll agree to disagree.... but Im right I can attach a boost gauge to an NA if you like.
The air is sucked in, in an NA but at WOT the air is sucked in fast enough to show atmospheric pressure at the manifold, the pressure differentials on NA engines through air filters and the like are almost negligible.

Technicially speaking the pressure will be a slight vacuum but not enough to show on a guage.

[derdle]

Old Fords had windscreen wipers that worked off the manifold vacuum....the faster the car went, the slower the wipers. Proves what confusionhunter is saying.

Paul