This is a difficult one..... especially if it doesn't have an EGT gauge already fitted
Personally, I would naturally fight for a better price, especially for a 2003, and with the money saved, I would spend the money on getting the head off and having a look at the condition of the pistons and sleeves etc. Maybe even get the Patrol down to a guy like Frans, who can open it up and check. If need be change the pistons and rings ( I'm no ZD30 expert, so I may be barking up the wrong tree ) and bearings, as this will cost almost nothing in comparison to having a blown up motor. Then fit an EGT gauge if not already fitted, and do the whole EGR removal/blanking, and all should be well. Those ZD motors are strong, and with the right precautions done to prevent the " big bang theory " you will have many happy Km.
I was never a fan of these motors, but over the years, after seeing what they are capable of, I have grown a little fond of them.
But you still can't beat cubic inches though......
Cedric, we all know by now that I am no diesel expert, but I want to say this:
In my opinion, leave the head right where it is, and rather have a sample of the engine oil analysed. This is much cheaper, and will tell you more than having a squiz at the pistons.
The problem is that the hand grenade failure is a fatigue-related failure due to recurring crystal structure change. Each time the aluminium components go over a certain temperature, the crystals start changing shape, but the complete transformation takes quite a long time (at least when compared to combustion cycle timescales). So effectively, some crystals change shape, shoving the surrounding crystals around, and causing stresses.
However, there will be absolutely no sign of this until the moment the fatigue limit is reached, in which case the piston virtually falls apart.
Thus, as far as I am aware, there is either no visible damage, or the grenade has blown, and the engine is very obviously broken.
So while nothing on earth will give you any warning of imminent hand-grenading, an oil analysis will give you a very good picture of the general health of the engine. It will for example tell you if there is too much diesel in the oil, which can indicate injector issues and thus predict the type of failure you had on your 4.2. It can also indicate if the engine has gotten hot, if there are head or head gasket issues and much more. All this for under R500, to my mind it should be something you do before buying any second-hand car.
Mag ons ons kenniskry met lekkerkry aanhoukry.