Very little! I had the air con condenser replaced under warranty by the non franchised dealer I purchased the car from. In the process they damaged the radiator which at my request was replaced at a BMW main agent. Since then the only thing I've had to replace is the LED/auto closure switch on the alarm.
This is my 2nd E34 525 in 4 years. The 24v is a great improvement on the 12v especially with the vanos. These are great cars but buy the best you can afford with the highest spec you can find! I'm lucky that mine has air, leather and electric roof. Many of them with air did not have the roof. The only negative comment I can make is that the 5 speed electronic auto box sometimes gets confused in traffic or stop start conditions. I'm currently looking at E39 528's at the moment. I hope they're as good!!
I had three excellent E34's and one disaster E39 (now sold). It's put me right off BMW for good.
My E34/91 is also good, only the automatic box was broken after 170.000km.
Go for an E39, they are great and you won't be disappointed. Very reliable.
Good luck.
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The E34 is the most reliable BMW ever. The 24valve non vanos especially - with just enough power to see off those silly little "Boy-Racers".
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