M535i General Information
The engine is more-or-less the same engine found in the US 535i, however with a few changes. Most noteably is the compression ratio, and power output. I have had no problems as of yet with the famous oil spray bar bolts, but have since replaced it as preventive maintenance. In anycase I will always be keeping an eye on that idle, which at the moment is fine. The engines are really bullet-proof if maintained well. Also, there are no head/head gasket problems on my car, VERY good. The only problem I have had with mine is that it has hesitation when started warm. This was due to the fuel pressure regulator, which I replaced. Also, my fuel transfer pump seems to be dying, cuz I have a hesitation under extreme acceleration with 1/8th left of fuel in the tank. This means no fuel because the main fuel pump is doing all the work and is being overworked. The transmission is excellent, with no problems and very direct. I'm going to use RedLine since in cold weather, it doesn't like shifting. The tranny bushings are going, and I'm going to have the check the guibo too soon. I sometimes get some driveline noises. The muffler will need replacing soon as well as some other exhaust components, though. Mufflers for these cars are somewhat expensive, as are any exhaust components. Water is condensing in the exhaust system, and I have plumes of white smoke coming out, no I should say out and around the exhaust tip! So yes, my exhaust system seems to be rusted out. :-)
Brakes
For originality, I've stuck with regular E28 brakes. However, there are some good modifications you can do to improve the already superior braking power. If memory serves, regular E28 535i front brakes are single-piston, 284mmx28mm or 288mmx28mm. M5 E28 brakes are 4-piston, 300x30mm. M5 brakes are a direct bolt-on to any E28 but you need 16" rims for caliper clearance. E32 brakes are a cheaper solution. E32 7-series brakes are single-piston, 302x28mm and also directly bolt on. Any E32 7-series, E34 5-series, and E31 8-series (as on my M5) brakes are also direct bolt-ons. About rear brakes, the only ones that fit an E28 are E28 M5 and any E34 5-series ONLY. E32 rears will not fit, although 740i calipers are the same as 540i/M5 (info thanks to Jason Lile at Zionsville Autosport, www.zionsvilleautosport.com).
The Suspension & Steering
The control arms have already been replaced at around 80,000 miles, but they're still shimmying. The steering box also needs to be checked for play or looseness periodically, but mine is fine. Also, I had the car aligned because of a vibration at more than 45 mph. My left toe alignment was toe-out!!! Otherwise everything was in spec. Now, my car has no vibrations and tracks true and straight. The bushings are going to be replaced with the beefed up versions (750il's, Steve D.'s, Bav Auto's, or Dinans are good).
The Interior & Electrics
Well, after diving into the electrics and making sure everything works, I discovered that the rear brake lights, back-up lights, and right front headlight were going on the fritz. Well, no bulbs needed replacing, and my original thoughts were right: the rear contacts needed sanding as they were corroded a bit, and same with the headlight. Also, the sanding off of the corrosion applies to ALL FUSES and the fuse box. I also have to soon replace the rubber gasket on the rear lights, as these are soon to be gone. The interior is in great shape, for cloth seats. The door panels have ripped a bit, and just buying a yard or two of new upholestery that matches, and doing a bit of stitching and glueing fixed them very well. The rear window regulators are notoriously slow, and my left rear window regulator needs replacing because a part broke. These are somewhat expensive (around $180), but worth getting if you're not so sure about them. I'm trying to find a junk yard with them. Zionsville Autosport has them for $75. Also, make sure all the A/C, buttons, radio, computer, etc. work on your car. I had to get the OBC picts from the E28 site in England in order to reset my computer, as my manual is in German! Overall, I'm happy with car, and all regular maintanence items are not too expensive and it's very easy to work on the car. I love it, and I'm a fanatic. Even though most people would've been extremely happy with my car as is, I HAVE to keep it in perfect condition. It's a disease I have.