2008 X5 3.0D 2nd engine failure in 2 months!

[jimbolambert]

Hi, I’m new here and am seeking some advice about my Dad’s 2008 X5 3.0 diesel (single turbo) in Australia . He has had the car about 3 years and has just experienced his second engine failure in 2 months! Car is fully maintained by a trustworthy local ex BMW master mechanic who installed an Autologic tune a year ago. First engine failure occurred when car was dropped off for a service (running fine?). Car had sat for little while and when the mechanic went to start it and it started making a tapping noise.
Turns out an injector was stuffed and cylinder 6 had a bent rod and a twisted crank. There was some water in the fuel, but not heaps. The mechanic suggested the injector failed open (in a big way) and flooded the cylinder with fuel after the motor was turned off. When the car was re-started the cylinder was full of fuel (and possibly some water) and caused a hydrolock.
All injectors were replaced along with the high pressure fuel pump. The motor was rebuilt with a new piston, rod, bearings and crank, and the head serviced. Huge $!

The car ran well for 6 or so weeks and then there were two sudden bangs whilst driving slowly and the car went into limp mode. There was heaps of error codes mostly related to cylinder 1. It turns out that cylinder 1 is now sitting about 20 thou" below TDC, so either has a bent rod or damaged gudgeon pin or bearing.

We don’t know yet if the new injector has also failed. Irrespective, I don’t see how enough fuel could possibly get in the combustion chamber to hydrolock whilst the motor is running. This leaves me thinking either too much boost or very wrong timing. I suspect either the ECU or the tune is at fault.

Car has run well after tune install and then in between failures. My dad mentioned some turbo whine at slow speeds, though I don’t know if that is normal or not.

I assume that the ECU won’t allow too high boost, unless the tune overrides that. Being a diesel, the combustion is compression related, but I wonder if the fuel charge is somehow occasionally firing too early. Though, there must be knock sensors.
I wonder if either the tune or ECU is experiencing an intermittent major melt down.
As it turns out Autologic who supplied the tune also does diagnostic equipment as well, so they are going to attempt to interpret the error codes to see if they can work out what is going wrong.

There is also the question of what to do with the engine now. The mechanic suggested that it may not be necessary to replace the con rod if the piston is only 20 thou" (0.5mm) below TDC. From what I have read 10 thou” is max allowable difference.
The tune is definitely coming out. I wanted to buy a replacement second-hand ECU, but the mechanic tells me that only a new ECU can be coded with the car.
We are so worried about rebuilding the motor, only to have it blow up again!
Does anyone have any other theories or suggestions?

Thanks for your help.