Is my reasoning correct here?

Dec 5, 2007
888
0
N W Leeds
Heres the observations/problems:
My police siren (Turbo) noise has disappeared to be replaced by more of a throaty wooshy/hissing sound when I floor throttle, but not quite as much oomph as usual and a bit of a delay at the same time - throttle response is usually instaneous. Engine light occasionally gets lit up
I'm assuming a dodgy air intake pipe after turbo somewhere. Theres also the occasional puff off white smoke from exhaust
But also my catch tank has filled with ALOT of fluid over past week (half full) - haven't checked if its oil, water or something else.
My thoughts are engine is overfueling due to boosted airleak causing a build up of excess diesel in cylinder this leads to either increased compression causing blowby on the pistions/rings putting fuel in the oil or just increasing the blowby due to the lubrication of the rings by diesel and putting up the crankcase pressure. There is quite a high positive pressure at idel with oil filler or dipstick removed.
Any ideas? Going to have a good look at week end.
 
Dec 5, 2007
888
0
N W Leeds
Sure enough the intercooler entry boost pipe had gone wonky and wasn't sealing. This is such a crap design by VAG, and they continue to do it.
The catch can was full of a mucky grey oilly mayo with waxed up diesel around the inlet/outlet tubes. I wonder how much the oil is contaminated with diesel now? If I hadn't had a catch tank this fuel would have just kept going round and round richer each time.
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
CrispDust wrote

Heres the observations/problems:
My police siren (Turbo) noise has disappeared to be replaced by more of a throaty wooshy/hissing sound when I floor throttle, but not quite as much oomph as usual and a bit of a delay at the same time - throttle response is usually instaneous. Engine light occasionally gets lit up


Police siren? Turbo noise? doesn't make any sense to me, I've never heard such a sound out of my car.

Hissing plus loss of performance points to a leak in the pressurised part of the inlet.

I'm assuming a dodgy air intake pipe after turbo somewhere. Theres also the occasional puff off white smoke from exhaust

White smoke is not usually fuel/oil, but steam. Water getting into the combustion chamber.

But also my catch tank has filled with ALOT of fluid over past week (half full) - haven't checked if its oil, water or something else.

Boost leak won't cause that.

My thoughts are engine is overfueling due to boosted airleak causing a build up of excess diesel in cylinder this leads to either increased compression causing blowby on the pistions/rings putting fuel in the oil or just increasing the blowby due to the lubrication of the rings by diesel and putting up the crankcase pressure.

Fascinating theory, utter bullshit. "build up of excess diesel in cylinder" - won't happen, can't happen, diesels run lean, taking in a full charge of air at each stroke. More fuel means a bigger bang, combined with soot if you're near the edge of the map - that's how a diesel's power output is controlled. If it were at all possible for liquid diesel (as opposed to vapourised diesel fuel from the injector) to build up the combustion chamber you'd get instant hydraulic lock and an exploded engine.

There is quite a high positive pressure at idel with oil filler or dipstick removed.
Any ideas? Going to have a good look at week end.


Sounds like you have worn bores or a broken piston ring, causing blowby which is pressurising your crankcase.

The catch can was full of a mucky grey oilly mayo with waxed up diesel around the inlet/outlet tubes.

Oh dear. Mayo means the head gasket has gone, you've got water in the oil. Head gasket and shot bores. Have you been giving it too many beans? The boost leak is just a coincidence.
 
Dec 5, 2007
888
0
N W Leeds
The mayo didn't have any water in - it was a diesel/oil mix -I've seen plenty of motor mayos in my time. (checked with a moisture meter too). NO mayo on oil filler cap, oil filter (removed and checked) or the dipstick.
Not a drop of coolant loss either.
So what puzzles me is how the diesel got into the crankcase?
After refixing the inlet pipes and checking all the others, cleaning the catch can to spotless I've done a 200 mile motorway round trip, no smoke and nothing but oil in the catchcan. Crnakcase pressure seems much lower (normal) to.
Might change oil anyway as a precaution.
Power was all where it should be, normal smooth and bags of torques even will car full of family.
MPG normal - 36mpg at steady 80
Weird.
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
Mayonnaise is an oil/water emulsion. If you have something that looks creamy, like mayonnaise, it's water + oil, either fuel oil or lubrication oil. If you aren't loosing coolant then it's condensation.

I'm not sure how you can tell that you have diesel oil in the crankcase? I for one would have some difficulty distinguishing it from lubrication oil. Even if you are getting quite serious blowby, you'll get combustion products in the crankcase, not unburned diesel.

Nothing is impossible, of course, merely very unlikely. You have a PD engine, where fuel is delivered to the pump injectors through channels in the head. I suppose it is just possible that your injector seals are faulty, allowing fuel oil into the cam housing, and from there down into the crankcase. Not very likely though.

36mpg at a steady 80 is not very good. I'd expect better than that from my aged TDI 110 - on the continent of course, where it would be legal.
 
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OLDOILER

Full Member
Jul 28, 2005
1,292
1
Wiltshire, UK
Sure enough the intercooler entry boost pipe had gone wonky and wasn't sealing. This is such a crap design by VAG, and they continue to do it.
The catch can was full of a mucky grey oilly mayo with waxed up diesel around the inlet/outlet tubes. I wonder how much the oil is contaminated with diesel now? If I hadn't had a catch tank this fuel would have just kept going round and round richer each time.
Mayo oil can also be toomany short runs also what is your drive profile? [ how many miles has the car done?] - I'm trying to think of things that are NOT expensive!!
 
Jul 23, 2008
720
0
Manchester - UNITED
Get rid of the catch tank.
Its very hard to get one to work correctly on these engines as I have discovered.
:cry:
Even if you just get rid of it for a bit and see if that helps matters. But I would recommend getting rid of it all together. :funk:

Dan
 
Dec 5, 2007
888
0
N W Leeds
The catch can works fine, although the exhaust tube is routed well underneath the care. Its amazing how much crap comes out of that crankcase breather.
I thought 36mpg at 80 was not too bad, its what I got before the remap - remember this is an Altea - not the most streamlined of Seats! And the BKD is less efficient than the older PD units.
Anyway all seems fine now, plenty of power, no strange noises, even the turbo whistle/whine at low revs has gone
 
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