Clueless (oil consumption mistery)

[neich]

Hi,

I am experiencing high oil consumption since I bought my VW T3 syncro with and 1.9TD AAZ installed. I have got 1 liter of oil per 300Km, which I think is way TOO MUCH. The problems is that the problem is still there after: new turbo, new valve seals and new piston rings. The cylinder head is in good condition (is a new one with less than 30K km, no craks). The engine does not leak oil, I am pretty sure.

So I am wondering how the oil is getting into the combustion chambers. The only place that I can think of is the PCV valve that connects to the turbo intake. Since the AAZ is installed at 52º instead at the original 15º, I always though that this valve cannot work properly, and that installing the 1.6TD JX valve cover could be a good idea since the PCV would work vertically then.

But I have installed the crankcase ventilation tube than connects to the PCV valve, and with the JX setup I think It wouldn't fit.

BTW, this ventilation tube has another version with an oil separator in the middle. The problem again is the 52º angle (I think that oil separator have to work vertically)

Any hint ?

Thanks
Nacho

[fspGTD]

So you just stuck new rings in there without replacing pistons?  Did you replace all 3 of the rings on each piston?  Did you hone the walls or have someone hone them who knows how to do it right?  Did you check the piston to cylinder wall clearance and make sure they didn't exceed VW's recommended wear limit (which is something very small, like .002"!  - at least on a 1.6lIDI Diesel.)?

I would bet that excessive blowby and thereby oil consumption is due to poorly sealing rings is your problem.  And even if you got a good hone, I wouldn't expect them to last very long with excessive piston to cylinder wall clearance (the stock wear limit, at least for a 1.6lIDI diesel is something like .002"!)

Or... depending on how "fresh" the rebuild is, maybe the rings haven't yet seated in.  They might just need some more time to seat in.  Don't use synthetic oil when breaking in the rings.  The hard chromium deposits on the wearing edges of the rings is very... um, hard.  You need the correct hone on the cylinder walls to wear the walls and rings together to a perfect match.  You could try a compression and/or leak down test if you are not sure about how well the rings are sealing.

[neich]

Well, thats a lot of info ... :-)

I didn't replace pistons since they were new when it was rebuit (that's my guess because they are not VW).  I replaced all three rings. They are oversize rings.  By the way,  I have replaced the rings AFTER teh rebuild, so

I didn´t check the piston to cylinder clearance. But since it is a rebuilt engine, I guess it should be ok. But .002 is ... small.

I am not using synthetic oil.

Would a compression test show if the sealing is ok ? I guess that after changing piston rings, the compression should be maximum.

Thanks
Nacho

[Pfhettinga]

I was in a simliar situation where i didn't know why my car was takeing oil, it was even take a bit of coolint aswell, then 4 months later after noticing these problems my crank pully went and had to do a full rebuild. you might want to check the crank pully just in case it's coming lose....