Author Topic: vnt's.... how do they die? (Read 6525 times)

DonGTI · « **on:** June 17, 2008, 02:28:33 pm »

abstract topic but my dad's mk4 golf (110 bhp 1.9 tdi) has 130,000 Km under its belt and the mechanic has told him to order a new vnt 15 since his should explode any minute... i told him i could get him a rebuild kit (tons of them on ebay) or maybe take it to a specialist turbo shop to rebuild it, however he insisted that vnt's at that milage are "beyond repair" and are a ticking timebomb...

is all this bullshyte? or as long as a VNT is still working it can be "saved" by a rebuild kit?

it has minimal up/down shaft play (tbh i've seen far worse) and engine is burning 300cc (i do dad's oilchanges myself after said mechanic broke sump drain TWICE) of 10w30 oil per 8000 km and does not smoke white (or black) so in my humble opinion it does not appear to be too bad.

can anyone shed me some light on this?

thanks
Daniel

jtanguay · « **Reply #1 on:** June 17, 2008, 03:49:02 pm »

what kind of oil are you running in it???

jimfoo · « **Reply #2 on:** June 17, 2008, 04:40:37 pm »

The turbine/shaft is hard to source, but the rest of the normal rebuild stuff is readily available on the net and elsewhere. It is actually the same as a GT15 from what I can see. The vanes can stick, but they are easy to clean, and if you don't drive it like a granny, they shouldn't get that bad. Also like any turbo, they can get damage from coking, like when you don't let them cool down after a drive.
Oh and obviously surge.

gigaz2 · « **Reply #3 on:** June 17, 2008, 04:57:38 pm »

Quote from: "DonGTI"

after said mechanic broke sump drain TWICEl

I believe that says it all as for that mechanics opinion..

I've seen them running quite perfectly with a lot of shaft play, and a seized one, but with care and the right maintenance they are pretty tough.

there's a post around here about a full stripdown.

DonGTI · « **Reply #4 on:** June 17, 2008, 09:55:27 pm »

Quote from: "jtanguay"

what kind of oil are you running in it???

10w30 fully synthetic Shell or Torco

Quote from: "gigaz2"

I believe that says it all as for that mechanics opinion..

if he just said all he said i wouldn;t be concerned, but he actually coughed up some ?fake possibly? vw service report that turbos be "replaced" after 130K Km since mean time between failures was 110-120K Km and thats what worried me...

Quote from: "jimfoo"

if you don't drive it like a granny

saddly he does drive granny style... tempted to just take it off and put in an SDI manifold (and keep the vnt to play around with it...) however he won't have any of that... if its a TDI he wants it to stay a tdi... even though when he drives it it is probably safe to say that it has never seen more than 2500 rpm's on it... once a week i drive it for 2-3 hours and try o make up for that :wink: but still probably internals al coked up

aidan · « **Reply #5 on:** June 18, 2008, 08:44:46 am »

I sold my Leon tdi with the same engine with 184k miles and original turbo and it was fine, that suggestion is bollocks

jtanguay · « **Reply #6 on:** June 18, 2008, 10:04:50 am »

hmm you might want to run a thicker oil. or go with that special Elf 0w30 oil if you really want it that thin. turbo's do like thin oil though. helps them spool up faster by reducing the friction even more.

lord_verminaard · « **Reply #7 on:** June 18, 2008, 10:53:56 am »

If it's never seen 2500 rpms very often then the vanes are probably stuck or gummed up pretty bad.

I'll offer a contrary opinion about the VNT15, it's a very weak turbo and the main cause of catastrophic failure is snapping of the turbine shaft. It is thin and can break very easily. I saw about a dozen of these failures when I worked for VW. If you are running any amount of boost higher than stock, like with a chip or otherwise, you are pretty much guaranteed of the turbine shaft breaking. VW should have put the much stouter VNT17 on these stock.

Brendan

gigaz2 · « **Reply #8 on:** June 18, 2008, 02:06:35 pm »

VW should have put the much stouter VNT17 on these stock.

and they do, now.. :x

I would go for the stuck vanes, a log from vag-com could be better diagnosing that.
if the car never sees more than that, the turbo is pratically new, a good cleanup and some maintenance and its ready for another couple hundred km.

if not, you can check the damage while its out

jtanguay · « **Reply #9 on:** June 18, 2008, 02:57:15 pm »

you could just install a water injection system to keep the vanes clear. or how about disabling the EGR?

DonGTI · « **Reply #10 on:** June 18, 2008, 03:30:10 pm »

vnt 17's and vnt 15's... there's more difference to them than just compressor size then?

jimfoo · « **Reply #11 on:** June 18, 2008, 07:37:42 pm »

Functionally they are the same, but the shaft is necked down between the two bearing contact points on the 15, and is a constant size on the 17 and above.

DonGTI · « **Reply #12 on:** June 18, 2008, 09:44:35 pm »

Thanks again Jimfoo, not sure if my eye deceives me but the 15 (necked down one then) looks thinner on the exhaust bit as well?

Regarding clogged vanes, should they move freely with actuator off? took his actuator apart (?jammed solid?) will not move any direction. Vane button/lever thing has about 5-8 mm of travel with lots of effort but not too much that i break things... is this normal?

Actuator for sure is screwed, hence bought a new actuator off ebay and looking for a complete rebuild kit right now, how complete should the kit be with the vanes i think stuck?

thanks
daniel

jimfoo · « **Reply #13 on:** June 18, 2008, 10:38:44 pm »

The diameters are the same. A 15 shaft will fit in a 17 and vice versa. The vanes should move freely, though the lever does have a fairly short range of travel. I haven't measured it. They can be taken apart and cleaned though, as it sounds like his needs to be.

jtanguay · « **Reply #14 on:** June 19, 2008, 03:35:43 am »

when taking it apart be sure to scribe the wheels to make sure that you put them back properly, as they are balanced.

Author Topic: vnt's.... how do they die? (Read 6525 times)

aidan