The first thing to realize is that an E34 is not Honda so it should not be treated like one. The E34 is a well build car, but it will require much more maintenance then say a Toyota Camry. Don’t pick up an E34 thinking you just got a $6,000 BMW. There is no such thing as a cheap BMW, period. Obviously, you will have to care about the car. The E34 is a very durable car and will easily roll over 200K miles, in style…

As with any used car, look for a well maintained example. Make sure you have the history of the car to check if it has been properly maintained. A pre-purchase inspection at reputable independent BMW specialist is definitely recommended.

Check if the car is leaking anything

• If the engine is cold, open the hood and open the radiator expansion tank cap and check how the coolant looks. Check if there isn’t any oil in the coolant, this would probably be because of a blown headgasket. Btw, it would probably be a good sign if you find blue colored coolant in there. BMW recommends a blue coolant, as do many BMW specialists, probably means the car was taken to reputable shops.
  
  Start the car and see how it idles. Rough idling might hint at overdue maintenance.
• Let it idle for quite a while to see if it doesn’t overheat.
• Check for hesitation while accelerating.
• Play with the controls, see if they function correctly
• Play with the heater and air conditioning, see if they work. If it’s an 89-92 E34 it might still be an R12 system, check if it’s been retrofitted to R134a.
• If it’s automatic, see if it shifts smoothly. BMWs with auto trannies seem to be a risk at over 100K miles. Many North American 6 cylinder BMWs also use GM trannies.
• Check if the car brakes well.
• Shimmy under hard braking means the thrust arm bushings have gone bad. If the car has over 80K miles, see if any front end suspension work has already been done. It’s very common for these cars to have balljoints and bushings go bad at 100K.
• Play with the window/sunroof switches, see if they work. The window switches might simply be dirty if the power windows don’t work. Easy to clean.
• Check the lower (plastic) door trims. If those are not there anymore or if they’re worn, see if rust isn’t creeping into the doors.
• If important to you, check if the cruise control still works
  

*Prices based US market value estimates, rough estimates... These cars are getting older so upkeep tends to dictate their value more than anyhthing else. The above numbers are just what you might roughly expect to pay for an E34.