So I have a 57 plate 2008 MY TDV8 bought recently with 112K or so on the clock. Full service history and drives very well most of the time. It now has 116K on it. Since we have had it occasionally the car will go into limp mode with the message 'Engine System Fault' on the LCD display and, usually, 'Special Programs Off' on the A/V screen. It has gradually been happening with increasing frequency, usually when driving steadily up hills although it has recently done it when just driving along steadily at 50mph. There do not seem to be any specific combinations of road/load conditions that trigger it.
My local independent LR specialist has looked at it in detail twice and has struggled to get the car to actually reproduce the fault on test drives but they eventually did, the first time they changed both EGR valves because one seemed to be stuck slightly open but that did not cure the problem. The fault code (there is only one that comes up) concerns inconsistent airflow readings into bank A. The second time the indy cleaned up both MAF sensors and switched them over to see if the fault moved with the sensor but it didn't, it's always bank A (i.e. passenger side).
I have checked for the usual suspects split hoses and just today a friend who is a professional car mechanic did a smoke test on the engine (i.e. using a special machine blew smoke under pressure into the bank B inlet hose from the intercooler end with the bank A hose disconnected and plugged) to check for any leaks from the inlet system. The smoke tester always showed a small flow rate so there is a small leak of some sort. There were none evident externally. Oddly though after a while some of the smoke seemed to be emerging from the Bank A side of the intercooler even though both intercooler top hoses were disconnected. Does anyone know if there are any normal connections between the inlet system after the intercooler and the system before the intercooler, other than the main hoses? Are the inlest air systems for bank A and bank B connected to each other?
The indy has said that when the car is running all the readings look in the normal range. My friend the mechanic has suggested it could be carbon build up on the turbo variable vanes and recommended running a bottle of Millers diesel additive through a tank of diesel and also running the car on Shell premium diesel for a tank or two to try to deal with any carbon build up.
One other thing is that the battery may be on its last legs, although the car always turns over strongly it does not take much in the way of extra load on the battery when the car isn't running (such as the mechanic's smoke machine) to cause it to need to be jump-started. Is it possible that this might somehow be a contributory factor? The car also seems to be less likely to fault after the fault code log has been cleared.
It would seem that the indy is at something of a loss to know what the problem is. Can anyone suggest anything?
I would be really grateful for any ideas.
Thanks, Nick Previously a 2008MY Tonga Green Vogue SE 3.6 TDV8

My mechanic friend did some more investigation today and smoke tested from the air filter side on the low pressure end of the inlet system on bank A. He found that smoke emerged from somewhere in the well behind the oil filter housing on the right hand side but he could not see the precise location.

Looking at the workshop manual that appears to be the area where the EGR cooler is located. However, the indy has recently changed the EGR valves on both sides so it would seem unlikely that is where the problem lies.

Can anyone offer any thoughts as to where the air leak may be coming from?

Hes also tells me the valley pan is discoloured with dried coolant and he suspects the thermostat housing. We have had a small coolant leak since we got the car. How difficult is that to fix?

Thanks for any input.

Nick Previously a 2008MY Tonga Green Vogue SE 3.6 TDV8