Just moved from E34 to E39 and I feel like SH...

[aabdelhamid]

Help I just baught a 97 E39 523i after driving my lovely 520i E34 1990 for a long period (thank god I did not sell it yet)
I have the following issues in the E39 and need guidance:
1) The computer does not detect the car by any means when connected to code the engine and gear box, it cannot communicate with the car and would not allow even recoding at all. Help me what can I do
2) The brakes when driving are mushy, the pedal sinks when the car is running and I brake and when the car is stationary and engine is not running the brakes do not sink. I am sure this is the servo, but what should I check exactly
3)The exhaust sounds like there is something loose, I checked everything and all rubber and bolts are OK. When I kick-down the exhaust sounds like a grinding wheel for a while ... any insights. I plugged the exhaust at the back and there are no leaks as far as I hear
4) The fan clutch is OK when the car is cold but once it heats up, the clutch does not disengage at all. My understanding is that the clutch engages till the car reaches a certain temerature and then it cools down the clutch soit disengages for a while and then engages again.

Please answer each one of those issue seperately as Iam just about selling the da.. thing again.
Thanks in advance
A very sad newly acquired E39 owner.

[wmann]

Not much help in the mechanical dept I am afraid, But I had a 1998 540i after a 1991 535i and sold the 1998 540i to get back into a 1995 540i/6sp.......You might want reconsider......the e34 in my opinion is much better made!

Best of luck.....Bill

[emw525E34]

Some insights that might help:
1) Need to have that computer looked at. Maybe just disconnect the battery and see what happens. This hard reset might cure the problem. A long shot but easy to do.
2) Get the brakes flushed by a garage. Its not costly. Put in only BMW Dot4 fluid pls.
3) The centre resonator may have rusted out and lose rusted metal might be vibrating inside. Had to take it apart tion inspect. Best to have it done in a muffler shop.
4) The fan clutch will NOT fully disengage. It just loosen and move at a slow speed. When idleing, if you can easily stop the fan blade using a thick GLOVED hand, then it is going south. I would say, replace it.

Yes, I know, it is disheartening to get a car knowing that it is newer and yet it is not running better than the old car. It happens. Just the usual fixes need to get it to the condition you wanted. You did not say if it is manual or steptronic, or what mileage it has. Good luck.