Let's attach a theme that will stay rather actual in the near future.
The failure causes the following sudden symptoms: loss of power, engine runs roughly (at three cylinders), loud knock at idle, smoke in the exhaust, crankcase gases pressure strongly rises.
When disassembling the engine, there are cracks are detected in one or more pistons (various sizes, up to a local ruptures). The look is radically different from the cases of usual piston melting, and only small local flowing can be observed in the areas of ruptures. The worst - when crack spread to the outer surface of the piston, it makes a deep scuffing at cylinder wall.
There is not a unique dependence on distance - usually failure occurs at 100-150.000 km, but few cases reported at range 50-100.000 km.
The problem recognized by Toyota, and described at technical service bulletins (TSB) EG-0172T-0511-EN on 06.05.2011, EG-0008T-0112 on 19.12.2012/09.18.2014, as well as in adjacent EG-0108T-1211 (for fuel system changes).
Considering the circumstances of occurrence, the cause of the problem should be called "inadequate strength margin of pistons" - that is constructive defects caused by mistake during on of engine modernization. Contributing factors are associated with the fuel system, but are secondary.
During 1KD-FTV production, there was various piston modifications installed. (Note: for standard pistons should formally specify the full number with the code of size group at the end (-01, -02, -03), but let's assume some simplification).
The first version can be considered as problem-free:
13101-30020 / 08.2000-08.2004 (Euro, Jap)
13101-30040 / 08.2002-07.2004 (Gen)
13101-30050 / 11.2002-12.2003 (Jap)
The documentation highlighted that for strengthening the area around the combustion chamber, there was a particular metal-fibrous structure fused in the piston crown.
The following modification coincided with the overall modernization - reduced compression ratio, the euro-modification torque up from 340 to 410 Nm (Japanese market 1KD never forced until the end of the production). The shape of the combustion chamber in the piston was changed essentially, and any mention about the reinforced zone disappeared.
13101-30060 / 12.2003-08.2006 (Jap), 08.2004-08.2006 (Euro)
Substitutability - compatible with the following "defective" version -30090.
Together with the introduction of the Euro 4 version and a slight output increase (up to 172 hp), most unsuccessful version of the pistons appeared. The phrase in Toyota's description "The strength of the pistons has been optimized through the use of high-strength materials in order to support the improved power output of the engine" today sounds mockingly.
13101-30090 / 08.2006-06.2009 (Euro), 08.2006-07.2007 (Jap).
Substitutability - compatible with the next version -30150.
Three years later, obviously substandard pistons was replaced by a new revision, but it has not brought success.
13101-30150 / 06.2009-12.2013
Substitutability - compatible with the latest version -30200.
Euro 5 modification of the engine with reduced compression ratio get new pistons and delivered to civilized market till the end of production. The piston problems was not mentioned for this version.
13101-30170 / 10.2010-06.2015
The final revision of pistons to replace -30150 -
13101-30200 / 12.2013-
If 1KD engine is available for more than fifteen years, why the topic has received considerable resonance recently?
As we can see, the failed pistons delivered to all world markets from 2006 to 2010 (to 2007 in Japan, when Toyota temporarily abandoned diesel for JDM). And the problem had a sufficient reflection on the forums - primarily Australian and British (unfortunately, the Japanese diesel engines have not come to the US market at that time). However, solution methods were too "civilized" - from the extended 7-year warranty and goodwill of dealer to $20.000 for the repair. But after -30170 piston modification was introduced the problem if not resolved, at least has become less relevant.
And what about the number of 1KD-FTV in Russia... At the LC Prado 120 era the vast majority (over 80%) of new cars sold with a gasoline V6, so potentially defective fleet in 2006-2009 added only 6-7000 cars. The amount of used car import in those years has become negligible against the sales of new. Hilux with a 3-liter engine was preferred by 30% of model customers, which add about 7000 cars at 2011-2014. The main 1KD number increase was due LC 150 Prado (75% of new cars sold with diesel) - about 60.000 cars. But the main sales have fallen to the most "fat years" / "los años de vacas gordas" in Russia (2011-2013), so many cars are still within warranty and didn't drive critical distance yet.
And once again we remind. This 70+ thousand cars still have to go to the secondary market. Therefore, instead of showing their broken pistons in the net, more practical owners acquainted with existing experience and solve the problem quietly, sometimes even using "goodwill" (for the relatively fresh post-warranty cars). So the words "constructive defect" cause their strongly opposition and even after publication of the TSBs they prefer drown this problem by traditional "low-quality fuel" and "heavy duty operation". It is not necessary to know everybody how they can buy "legendary reliable" Toyota and obtain a certain probability of the repair cost comparable to car half-price.
The advices for 1KD users are simple - be very careful with the chip tuning, avoid long driving at high speeds, especially under load or at high ambient temperature... And there is the most radical method always in stock - the preventive installation of latest revision pistons.