I just purchased a 1990 850i german spec. Bought it from a german mech from Fla who worked for bmw in germany. The car is in very good cond. new tires, new shocks ,new break pads, new fuel pump, new bushings prior to purchase by seller. Color is Mauritius Blue. Black and grey interior. I noticed that I have engine heat coming in when ac not running. Also temp gauge went to about 65% nearer the overheating line but no engine lights . It was doing this off and on would cool back when driving. Is this a water pump or radiator core prob. I also have some pulsating on the break pedal when idle in drive. Indicator light flashes for less than a second. Gauges are in german so I was not sure but think it is the brake booster and power steering indicator.
Horn also has a problem it stays on when I put the fuse in. After driving today and letting it sit went to start and made a loud gurgaling noise and could smell radiator fluid ever so slightly but no leaks at all. Other than that car drives smooth and shifts perfect. This model also has the s sport drive like the CSI very nice when driving in this mode. Need some direction this is not my daily driver only a weekend nice day car I drive a 525i as a daily. Thanks hope its not to many ?. I expect to spend some $ on maintenance but not get mis guided by a local mech who does not understand 850s. Car has 61,500 original miles.Any ball park $ figures would be great. Thanks Again.

Starting with the heat coming in--good possibility that it is a broken/stuck heater valve.

The most important is the high temperature indication. The system needs to be bled to get the air out. That is the gurgle too.

If the overflow tank is yellow on the bottom, replacing it before it blows up is a priority.

If the radiator cap doesn't have the number 200 on it replacement is very important. The un-numbered cap is a danger to the cooling system integrity.

The horns are probably smashed--they are located under the nose where a curb can wipe them off. Add a stuck relay in the fuse box under the hood.

Lots of reading material in the links in my signature--bleeding the radiator should be on the e31faq site.

Check both fans. the one in front of the radiator should come on with the AC compressor. The one on the water pump should not stop when you test it with a rolled up newspaper.

A single overheat has been known to damage a v12 so the most important thing is the coolant system.

The brakes have a couple of possibilities that are also included in the literature.

Thanks Terry y look forward to more insight on this forum