boost leak - 1.8T

[kermac]

It's a while since I've been on the forum. Greetings to anyone who remembers me!

I still have my trusty MY2000 A4 1.8T quattro and had a (second) replacement engine fitted not long ago. All good except it suddenly developed a boost leak - major (perhaps 50%) loss of power, whooshing noise from under the bonnet as well as quite a lot of turbo whine rising and falling with demand on the turbo (this could be the best clue - I haven't seen this reported on the other forums).

Nothing to show on VCDS of course except:

00561 - Mixture Adaptation

13-10 - Adaptation Limit (Mul) Not Reached - Intermittent

First check was to the turbo outlet pipe but no sign of a split. So I inserted a tyre valve permanently into the inlet system and connected the air compressor. PLenty of air going in, but it was all coming straight out somewhere - not pressurising at all. I couldn't tell where but it sounded like it was somewhere beneath the intake manifold. I couldn't pinpoint it even with a home-made stethoscope, but I had expected it to come from the other side of the engine in view of the turbo whine.

The car is driveable, but I'm reluctant to do anything more than logging which seems fairly pointless atm. Anyone got any suggestions? She's got a GTRS and associated bits and pieces, but internals are stock.

All advice gratefully received...

Kerry

 

[jnrdavo]

smoke test to check for leaks?

Sent from my SM-S926B using Tapatalk

 

[kermac]

smoke test to check for leaks?

Sent from my SM-S926B using Tapatalk

Thanks Stu (it is Stu isn't it?)

I don't have the equipment to do a smoke test. Perhaps there's a simple way to do smoke apart from taking up ciggies?? Anyway, that would be making it too easy

I have the compressor fitted to the pipe between the i/c and the inlet manifold, but each time I try to pressurise the system the sound of escaping air seems to come from a different direction. But definitely on the inlet side... Can't feel the air anywhere with my hand when I activate the compressor (20psi, oil cap off).

There's a big fat moulded plastic pipe around 3-4cm round directly under the manifold running north-south and curling down into the block at one end, exiting into a connector with two rubber hoses at the other. What might this be? Crankcase ventilation? It doesn't feature in any of the schematics in my Bentleys or online pics. Looks like the sort of thing that might crack, but as I say I can't detect any leak coming from it.

I've already had the charge pipe running from the turbo to the cross-pipe off (other side) - no sign of a split.

It's been a long time since I've had my head under the bonnet...

 

[kermac]

This looks like the breather hose I mentioned above although it's actually upside down in the pic. Mfg part no is 058198298, available from an Aus parts distributor. The same part number also appears on ecs but it's a completely different shape. This could be because they don't have AJL motors in the US?
Either way, I can't detect a split or problem with the pipe, either by touch or by running compressed air through the system. The source of the leak is still a mystery (why does this have to be so complicated for a young codger?)

 

[smit2100]

This looks like the breather hose I mentioned above although it's actually upside down in the pic. Mfg part no is 058198298, available from an Aus parts distributor. The same part number also appears on ecs but it's a completely different shape. This could be because they don't have AJL motors in the US?
Either way, I can't detect a split or problem with the pipe, either by touch or by running compressed air through the system. The source of the leak is still a mystery (why does this have to be so complicated for a young codger?)

View attachment 33363

@kermac . I associated that sig with Frankenstein ( sorry Franken ) turbos if I recall correctly back in the day. I just went with German crafted lobas vs Chinese knockoff but paid accordingly. Great to see you still have the car. I suppose once a boost junky always a boost junky and that boost hit . Keeps that little hoon bast$&d inside in check). I can’t talk, I have access to be able punt around in a twin turbo v6 still. But I just upgraded to something more reliable but still b5 s4 vintage eg 996 turbo. Much much much more reliable. Boost least, WTF is that. Biggest issues in nearly 10 years was a key cylinder issue and a leaking diff seal which I am getting sorted this month. . Helps when you start tweaking a car that puts out 420hp from the factory floor at the turn of the century. B5 S4 wrong car to tweak. Wish I had saved the extra pennies and was a little more patient and brought a b5 rs4 back in 2008 instead of the s4. But How times have changed. Now to really eliminate those boost leaks, after a circa 10 year Audi cleansing, I am back with 4 rings after getting an itch that took 6 years to stop scratching. Eg If you want the apex of factory power and last century tech, and no forced induction and associated boost leaks I went straight to the apex of Audi power in the form of 5.2l v10. . Never would I imagined having an R8. Back in the day, when I was searching for my b5s4, only the v8 R8 was in existence at a circa 15 multiplier of what I paid for my b5 s4 which was one of the lowest priced examples on the market at 23k. B5rs4’s had a 4 out front with low k’s back in circa 2008.

So the R8 came with a caveat, strictly V106MT. ( makes for a good number plate). A mere 6 years to land one within my budget. But as good as it is, like you, need that boost hit. The NA is a bit nah.

 

[jnrdavo]

not sure what else you can do at home mate... soapy water on the pipes to see if you can see air bubbles?

And yes, it's Stu

 

[kermac]

@kermac . I associated that sig with Frankenstein ( sorry Franken ) turbos if I recall correctly back in the day. I just went with German crafted lobas vs Chinese knockoff but paid accordingly. Great to see you still have the car. I suppose once a boost junky always a boost junky and that boost hit . Keeps that little hoon bast$&d inside in check). I can’t talk, I have access to be able punt around in a twin turbo v6 still. But I just upgraded to something more reliable but still b5 s4 vintage eg 996 turbo. Much much much more reliable. Boost least, WTF is that. Biggest issues in nearly 10 years was a key cylinder issue and a leaking diff seal which I am getting sorted this month. . Helps when you start tweaking a car that puts out 420hp from the factory floor at the turn of the century. B5 S4 wrong car to tweak. Wish I had saved the extra pennies and was a little more patient and brought a b5 rs4 back in 2008 instead of the s4. But How times have changed. Now to really eliminate those boost leaks, after a circa 10 year Audi cleansing, I am back with 4 rings after getting an itch that took 6 years to stop scratching. Eg If you want the apex of factory power and last century tech, and no forced induction and associated boost leaks I went straight to the apex of Audi power in the form of 5.2l v10. . Never would I imagined having an R8. Back in the day, when I was searching for my b5s4, only the v8 R8 was in existence at a circa 15 multiplier of what I paid for my b5 s4 which was one of the lowest priced examples on the market at 23k. B5rs4’s had a 4 out front with low k’s back in circa 2008.

So the R8 came with a caveat, strictly V106MT. ( makes for a good number plate). A mere 6 years to land one within my budget. But as good as it is, like you, need that boost hit. The NA is a bit nah.

Hi Smit
Thanks for your post. Very interesting.
Do you know anything about boost leaks?
PS Yes I went for a Frankenturbo on my Mk1 TT. Pretty good. But the engine dropped out of the car and hit the road on a tour of Tasmania with the g/f years ago. Ian G bought the sad remains along with a spare engine and restored it into a beautiful car

 

[kermac]

not sure what else you can do at home mate... soapy water on the pipes to see if you can see air bubbles?

And yes, it's Stu

Thanks Stu. I keep reminding myself to try the soapy water trick but after a while of getting oil up to my armpits I sort of lose interest for a couple of days...

 

[smit2100]

I had a boost leak tester for my b5 s4 and have one for my 996 turbo but I just let my mechanics use it/ diagnose it.

 

[spaz]

Check all your one way valves if you still have egr

 

[quattro5v]

Plastic end tanks on the SMIC?

Check the connections at the turbo outlet, the cross-over inlet (which goes underneath the radiator), the cross-over outlet into the SMIC inlet, the SMIC outlet, and the TB. If you're hearing a whizzing sound (or louder turbo sounds in time with the turbo spooling) then its one of the "bigger" hoses you'd need to check. A crack or failure within the smaller vacuum hoses usually doesn't result in the turbo sounds becoming louder/amplified.

Another one to check would be your diverter valve (if its still intact), the diverter valve hose section which goes back to your airbox, and the diverter hose itself (could be split or broken). **That's only if you still have a standard style diverter valve there**

(Yep - still here)