sausage fingers wrote:When I bought Helga she had an Audi TD AAZ engine which has thrown all the coolant and seized.
Any engine will seize without coolant. It will be caused by some other failure first, eg head gasket gone, burst hose, previous damage from abuse in donor car, all sorts of possible reasons for the failure, but it's not because it's an AAZ.
sausage fingers wrote: Half the people I have spoken too say running a syncro with an AAZ is too much bus for the engine.
Sorry to be blunt, but this is nonsense.
Many Syncros left the factory with a smaller diesel engine (1.6TD JX) than you have, and the AAZ has been the most popular upgrade route for years. The AAZ is a good strong engine, and there are many of them out there happily pushing Syncros uphill for many 1000s of miles without trouble. I had an AAZ in my Syncro which was equally happy mud wading and hill climbing in Wales/Scotland or cruising down to Bavaria on the Autobahns at 4000rpm for hours. Never had any engine problems and was still running brilliantly when I reluctantly sold it. Have done several AAZ conversions myself for customers - none have reported any subsequent problems.
My advice would be to replace like for like with a
good AAZ (that can ideally be seen running in the donor car first). Perhaps you could buy a Golf/Passat/Seat/Audi80 with one in for a few hundred pounds and run around in it for a week or two before pulling it out to put in the van (but maybe not possible for you if your van's needed back on the road in a hurry).
A word of caution if considering the Tdi upgrade. They may be more powerful, but it is a more complicated conversion so will cost a lot more to do in labour and parts, must be done well or may be less reliable, and if the syncro is too much bus for the AAZ then the Tdi may well be too much engine for the Syncro box without an Aiden rebuild with taller gearing (as mentioned above).