Turbo Failures - anyone?

[glend]

I have been following a few turbo failure discussions over on LOST. It is apparent that the US owners of KJ CRDs seem to have a fair number of turbo failures often with other disasterous consequences - engine oil starvation and bearing failures. I was just wondering if there a have been any similiar turbo failures here in Australia? I have not run across much discussion of this on AJOR.

Here is the LOST thread, and I have waded in near the end questioning how they could have so many for so few vehicles when we seem to avoid it even though we have CRDs back to the early KJ 2.5L CRD years.

http://www.lostjeeps.com/forum/phpBB...752912#p752912

Common sense seems to indicate that good clean synthetic oil (of the right specification), paying attention to the turbo cool down, and watching your exhaust gas temperatures, will minimise the problem.

There is a turbo spool bearing description below:

There are NO MOVING PARTS inside the center cartridge of the turbo other than the center shaft of steel. That shaft passes through several small "bushings" on either end of the cartridge, a large thrust bearing on the compressor side, and into the main bearing: a carefully machined -yet solid- tube of brass. This brass tube precisely fits the steel shaft (If it hasn't overheated) and has several VERY TINY grooves and holes cut in it for the oil to flow through. The oil is the only thing moving in the turbo, supporting and cooling the center shaft entirely. In proper operation, the shaft would be completely covered and supported, and never touch the brass tube or anything else other than the thrust bearings at either end.

Those thrust bearings are the only thing that keeps the oil in - And they are solid little pieces of metal too. There are also no "seals" in the turbo that could possibly fail. The ONLY FAILURE MODE of the turbo is shaft damage to these other parts. The highly precise tolerances wear out from physical contact, and it overheats and begins to leak oil... Overheating more and leaking more... until it is replaced or the shaft seizes and snaps off.

Obviously any contaminants suspended in the oil (such as soot particles) will have an abrasive effect on these oil channels (grooves) cut in the bearing face and can accelerate the wear in the space between the shaft and the bearing surface. This seems to me to be a big argument for the elimination of EGR. Maybe a Magfilter would be a good idea as well.

Finally, while I am certainly no expert on this, that the expansion coefficient of Brass and Steel is different, and
seems to me that the Brass bearing tube that supports the steel shaft will expand more than the steel shaft and potentially squeeze the shaft and put more stress on the oil film that is separating the two components. I'd appreciate a more knowledgable take on this topic.

I assume the space between the two is much greater when cold and they expand individually to the design tolerance at operating tempterature (whatever Garrett determined that to be). The play in the shaft that you can feel when the unit is cold (the wiggle test) is a pretty useless approximation based on feel.

Any ideas for keeping this area cooler? An oil cooler perhaps?