audi a3 overheat problem

I own a 1997 A3 1.6 sport. A few weeks ago the engine overheated.I took it to my mechanic who has serviced the car for the past 3 yrs. Water had got into the oil so we presumed the head gasket needed
replacing - it did.He stripped down the head and had it serviced by specialist.After refitting he discovered that the impeller in the water pump had failed (the plastic had actually melted and broken up causing a blockage in the radiator which was also then replaced). This was fast becoming an an expensive repair but worse was to follow. After a few days of having the car back and only 60-70 miles it began to run erratically: 3 of the spark plugs had fouled up and the car was burning oil at a rapid rate. My mechanic thinks this is caused by the piston oil seals being damaged when the car overheated - obviously another expensive job to repair. So the questions I have are 1) is this the likely cause of the oil burning problem or is there another cause (valve seals?) 2)Would it be cheaper to replace entire engine? 3)Is the AEH engine the same as an AKL for straight swap? Would be grateful for any help/advice Dave
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Thanks Graham I spoke to Audi uk,and the local dealership and their basic attitude was 'tough luck' on account that I'd not had the car serviced by Audi.I explained that the service schedule had been carried out for the 3 yrs I have owned the vehicle to the letter, albeit by my very thorough and competent mechanic, but this did'nt seem to matter (before this it had been serviced by Audi). Your experience with the water pump may be the answer to my mechanics problem as he was struggling to work out what had failed first - it was a chicken and egg type scenario! I'll go back to Audi and try again with this new info. Thanks once again, Dave
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